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17 pages, 1067 KiB

Open AccessArticle

The Hydrophobic Effect Studied by Using Interacting Colloidal Suspensions

by Francesco Mallamace, Giuseppe Mensitieri, Martina Salzano de Luna and Domenico Mallamace

Int. J. Mol. Sci. 2023, 24(3), 2003; https://doi.org/10.3390/ijms24032003 - 19 Jan 2023

Viewed by 1542

Abstract

Interactions between nanoparticles (NPs) determine their self-organization and dynamic processes. In these systems, a quantitative description of the interparticle forces is complicated by the presence of the hydrophobic effect (HE), treatable only qualitatively, and due to the competition between the hydrophobic and hydrophilic [...] Read more.

Interactions between nanoparticles (NPs) determine their self-organization and dynamic processes. In these systems, a quantitative description of the interparticle forces is complicated by the presence of the hydrophobic effect (HE), treatable only qualitatively, and due to the competition between the hydrophobic and hydrophilic forces. Recently, instead, a sort of crossover of HE from hydrophilic to hydrophobic has been experimentally observed on a local scale, by increasing the temperature, in pure confined water and studying the occurrence of this crossover in different water–methanol solutions. Starting from these results, we then considered the idea of studying this process in different nanoparticle solutions. By using photon correlation spectroscopy (PCS) experiments on dendrimer with OH terminal groups (dissolved in water and methanol, respectively), we show the existence of this hydrophobic–hydrophilic crossover with a well defined temperature and nanoparticle volume fraction dependence. In this frame, we have used the mode coupling theory extended model to evaluate the measured time-dependent density correlation functions (ISFs). In this context we will, therefore, show how the measured spectra are strongly dependent on the specificity of the interactions between the particles in solution. The observed transition demonstrates that just the HE, depending sensitively on the system thermodynamics, determines the hydrophobic and hydrophilic interaction properties of the studied nanostructures surface. Full article

(This article belongs to the Special Issue Feature Papers in Physical Chemistry and Chemical Physics 2022)

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18 pages, 4706 KiB

Open AccessArticle

Crystal Structure and Chemical Bonds in [Cu^II₂(Tolf)₄(MeOH)₂]∙2MeOH

by Irena Majerz and Marta S. Krawczyk

Int. J. Mol. Sci. 2023, 24(2), 1745; https://doi.org/10.3390/ijms24021745 - 16 Jan 2023

Viewed by 1748

Abstract

A new coordination compound of copper(II) with a tolfenamate ligand of the paddle-wheel-like structure [Cu^II₂(Tolf)₄(MeOH)₂]∙2MeOH was obtained and structurally characterized. Chemical bonds of Cu(II)∙∙∙Cu(II) and Cu(II)–O were theoretically analyzed and compared with the results for selected [...] Read more.

A new coordination compound of copper(II) with a tolfenamate ligand of the paddle-wheel-like structure [Cu^II₂(Tolf)₄(MeOH)₂]∙2MeOH was obtained and structurally characterized. Chemical bonds of Cu(II)∙∙∙Cu(II) and Cu(II)–O were theoretically analyzed and compared with the results for selected similar structures from the CSD database. QTAIM analysis showed that the Cu(II)∙∙∙Cu(II) interaction has a strength comparable to a hydrogen bond, as indicated by the electron density at a critical point. The remaining QTAIM parameters indicate stability of the Cu(II)∙∙∙Cu(II) interaction. Other methods, such as NCI and NBO, also indicate a significant strength of this interaction. Thus, the Cu(II)∙∙∙Cu(II) interaction can be treated as one of the noncovalent interactions that affects the structure of the coordination compound, the packing of molecules in the crystal, and the general properties of the compound. Full article

(This article belongs to the Special Issue Feature Papers in Physical Chemistry and Chemical Physics 2022)

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12 pages, 3797 KiB

Open AccessArticle

The Use of Electrochemical Methods to Determine the Effect of Nitrides of Alloying Elements on the Electrochemical Properties of Titanium β-Alloys

by Jitřenka Jírů, Vojtěch Hybášek, Petr Vlčák and Jaroslav Fojt

Int. J. Mol. Sci. 2023, 24(2), 1656; https://doi.org/10.3390/ijms24021656 - 14 Jan 2023

Viewed by 1556

Abstract

Titanium beta alloys represent the new generation of materials for the manufacturing of joint implants. Their Young’s modulus is lower and thus closer to the bone tissue compared to commonly used alloys. The surface tribological properties of these materials should be improved by [...] Read more.

Titanium beta alloys represent the new generation of materials for the manufacturing of joint implants. Their Young’s modulus is lower and thus closer to the bone tissue compared to commonly used alloys. The surface tribological properties of these materials should be improved by ion implantation. The influence of this surface treatment on corrosion behaviour is unknown. The surface of Ti-36Nb-6Ta, Ti-36Nb-4Zr, and Ti-39Nb titanium β-alloys was modified using nitrogen ion implantation. X-ray photoelectron spectroscopy was used for surface analysis, which showed the presence of titanium, niobium, and tantalum nitrides in the treated samples and the elimination of less stable oxides. Electrochemical methods, electrochemical impedance spectra, polarisation resistance, and Mott–Schottky plot were measured in a physiological saline solution. The results of the measurements showed that ion implantation does not have a significant negative effect on the corrosion behaviour of the material. The best results of the alloys investigated were achieved by the Ti-36Nb-6Ta alloy. The combination of niobium and tantalum nitrides had a positive effect on the corrosion resistance of this alloy. After surface treatment, the polarization resistance of this alloy increased, 2.3 × 10⁶ Ω·cm², demonstrating higher corrosion resistance of the alloy. These results were also supported by the results of electrochemical impedance spectroscopy. Full article

(This article belongs to the Special Issue Feature Papers in Physical Chemistry and Chemical Physics 2022)

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13 pages, 699 KiB

Open AccessArticle

Excess Absorbance as a Novel Approach for Studying the Self-Aggregation of Vital Dyes in Liquid Solution

by Antonio Minó, Lucio Zeppa and Luigi Ambrosone

Int. J. Mol. Sci. 2023, 24(2), 1645; https://doi.org/10.3390/ijms24021645 - 13 Jan 2023

Cited by 3 | Viewed by 1704

Abstract

In the present paper, a simple method for analyzing the self-aggregation of dyes in a solution by a UV-visible absorption measurements is proposed. The concept of excess absorbance is introduced to determine an equation whose coefficients determine the parameters of the aggregation equilibrium. [...] Read more.

In the present paper, a simple method for analyzing the self-aggregation of dyes in a solution by a UV-visible absorption measurements is proposed. The concept of excess absorbance is introduced to determine an equation whose coefficients determine the parameters of the aggregation equilibrium. The computational peculiarities of the model are first discussed theoretically and then applied to sodium fluorescein in polar protic and aprotic solvents, as well as in aqueous solutions of methylene blue, which is a cationic dye. Although the experimental responses are very different, the model appears to work equally well in both cases. The model reveals that the trimer is the most likely configuration in both solvents. Furthermore, aggregation is strongly favored for the protic solvent. Interestingly, the model establishes that in aqueous solutions of methylene blue, the tetramer is the predominant form, which has long been assumed and recently demonstrated with sophisticated computational techniques. Full article

(This article belongs to the Special Issue Feature Papers in Physical Chemistry and Chemical Physics 2022)

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22 pages, 10050 KiB

Open AccessArticle

Unraveling the Nature of Hydrogen Bonds of “Proton Sponges” Based on Car-Parrinello and Metadynamics Approaches

by Beata Kizior, Mariusz Michalczyk, Jarosław J. Panek, Wiktor Zierkiewicz and Aneta Jezierska

Int. J. Mol. Sci. 2023, 24(2), 1542; https://doi.org/10.3390/ijms24021542 - 12 Jan 2023

Viewed by 2715

Abstract

The nature of intra- and intermolecular non-covalent interactions was studied in four naphthalene derivatives commonly referred to as “proton sponges”. Special attention was paid to an intramolecular hydrogen bond present in the protonated form of the compounds. The unsubstituted “proton sponge” served as [...] Read more.

The nature of intra- and intermolecular non-covalent interactions was studied in four naphthalene derivatives commonly referred to as “proton sponges”. Special attention was paid to an intramolecular hydrogen bond present in the protonated form of the compounds. The unsubstituted “proton sponge” served as a reference structure to study the substituent influence on the hydrogen bond (HB) properties. We selected three compounds substituted by methoxy, amino, and nitro groups. The presence of the substituents either retained the parent symmetry or rendered the compounds asymmetric. In order to reveal the non-covalent interaction properties, the Hirshfeld surface (HS) was computed for the crystal structures of the studied compounds. Next, quantum-chemical simulations were performed in vacuo and in the crystalline phase. Car–Parrinello molecular dynamics (CPMD), Path Integral Molecular Dynamics (PIMD), and metadynamics were employed to investigate the time-evolution changes of metric parameters and free energy profile in both phases. Additionally, for selected snapshots obtained from the CPMD trajectories, non-covalent interactions and electronic structure were studied. Quantum theory of atoms in molecules (QTAIM) and the Density Overlap Regions Indicator (DORI) were applied for this purpose. It was found based on Hirshfeld surfaces that, besides intramolecular hydrogen bonds, other non-covalent interactions are present and have a strong impact on the crystal structure organization. The CPMD results obtained in both phases showed frequent proton transfer phenomena. The proton was strongly delocalized in the applied time-scale and temperature, especially in the PIMD framework. The use of metadynamics allowed for tracing the free energy profiles and confirming that the hydrogen bonds present in “proton sponges” are Low-Barrier Hydrogen Bonds (LBHBs). The electronic and topological analysis quantitatively described the temperature dependence and time-evolution changes of the electronic structure. The covalency of the hydrogen bonds was estimated based on QTAIM analysis. It was found that strong hydrogen bonds show greater covalency, which is additionally determined by the proton position in the hydrogen bridge. Full article

(This article belongs to the Special Issue Feature Papers in Physical Chemistry and Chemical Physics 2022)

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21 pages, 1532 KiB

Open AccessArticle

Predicting the Electronic Absorption Band Shape of Azobenzene Photoswitches

by Ricard Gelabert, Miquel Moreno and José M. Lluch

Int. J. Mol. Sci. 2023, 24(1), 25; https://doi.org/10.3390/ijms24010025 - 20 Dec 2022

Cited by 3 | Viewed by 2504

Abstract

Simulations based on molecular dynamics coupled to excitation energy calculations were used to generate simulated absorption spectra for a family of halide derivatives of azobenzene, a family of photoswitch molecules with a weak absorption band around 400–600 nm and potential uses in living [...] Read more.

Simulations based on molecular dynamics coupled to excitation energy calculations were used to generate simulated absorption spectra for a family of halide derivatives of azobenzene, a family of photoswitch molecules with a weak absorption band around 400–600 nm and potential uses in living tissue. This is a case where using the conventional approach in theoretical spectroscopy (estimation of absorption maxima based on the vertical transition from the potential energy minimum on the ground electronic state) does not provide valid results that explain how the observed band shape extends towards the low energy region of the spectrum. The method affords a reasonable description of the main features of the low-energy UV-Vis spectra of these compounds. A bathochromic trend was detected linked to the size of the halide atom. Analysis of the excitation reveals a correlation between the energy of the molecular orbital where excitation starts and the energy of the highest occupied atomic orbital of the free halide atom. This was put to the test with a new brominated compound with good results. The energy level of the highest occupied orbital on the free halide was identified as a key factor that strongly affects the energy gap in the photoswitch. This opens the way for the design of bathochromically shifted variants of the photoswitch with possible applications. Full article

(This article belongs to the Special Issue Feature Papers in Physical Chemistry and Chemical Physics 2022)

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13 pages, 2114 KiB

Open AccessArticle

Anion-Controlled Synthesis of Novel Guanidine-Substituted Oxanorbornanes

by Luka Barešić, Davor Margetić and Zoran Glasovac

Int. J. Mol. Sci. 2022, 23(24), 16036; https://doi.org/10.3390/ijms232416036 - 16 Dec 2022

Cited by 4 | Viewed by 1917

Abstract

The cycloaddition of simple alkyl-substituted guanidine derivatives is an interesting approach toward polycyclic superbases and guanidine-based organocatalysts. Due to the high nucleophilicity of guanidines, an aza-Michael reaction with dienophiles is more common and presents a huge obstacle in achieving the desired synthetic goal. [...] Read more.

The cycloaddition of simple alkyl-substituted guanidine derivatives is an interesting approach toward polycyclic superbases and guanidine-based organocatalysts. Due to the high nucleophilicity of guanidines, an aza-Michael reaction with dienophiles is more common and presents a huge obstacle in achieving the desired synthetic goal. Our preliminary investigations indicated that the proton could act as a suitable protecting group to regulate the directionality of the reaction. To investigate the role of the protonation state and type of anion, the reactivity of furfuryl guanidines with dimethyl acetylenedicarboxylate was explored. Furfuryl guanidines showed a strong reaction dependence on the nucleophilicity of the counterion and the structure of guanidine. While the reaction of DMAD with the guanidinium halides provided products of an aza-Michael addition, Diels–Alder cycloaddition occurred if non-nucleophilic hexafluorophosphate salts were used. Depending on the structure and the reaction conditions, oxanorbornadiene products underwent subsequent intramolecular cyclization. A tendency toward intramolecular cyclization was interpreted in terms of the pK_a of different positions of the guanidine functionality in oxanorbornadienes. New polycyclic guanidines had a slightly decreased pK_a in acetonitrile and well-defined geometry suitable for the buildup of selective sensors. Full article

(This article belongs to the Special Issue Feature Papers in Physical Chemistry and Chemical Physics 2022)

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10 pages, 2343 KiB

Open AccessArticle

Piezoelectric and Magnetoelectric Effects of Flexible Magnetoelectric Heterostructure PVDF-TrFE/FeCoSiB

by Dandan Wen, Xia Chen, Fuchao Huang, Jingbo Zhang, Pingan Yang, Renpu Li, Yi Lu and Yu Liu

Int. J. Mol. Sci. 2022, 23(24), 15992; https://doi.org/10.3390/ijms232415992 - 15 Dec 2022

Cited by 6 | Viewed by 2117

Abstract

Flexible polymer-based magnetoelectric (ME) materials have broad application prospects and are considered as a new research field. In this article, FeCoSiB thin films were deposited on poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE) substrate by DC magnetron sputtering. The structure of PVDF-TrFE/FeCoSiB heterostructure thin films was similar [...] Read more.

Flexible polymer-based magnetoelectric (ME) materials have broad application prospects and are considered as a new research field. In this article, FeCoSiB thin films were deposited on poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE) substrate by DC magnetron sputtering. The structure of PVDF-TrFE/FeCoSiB heterostructure thin films was similar to 2-2. Under a bias magnetic field of 70 Oe, the composites have a dramatically increased ME voltage coefficient as high as 111 V/cm⋅Oe at a frequency of about 85 kHz. The piezoelectric coefficient of PVDF-TrFE thin films is 34.87 pC/N. The surface morphology of PVDF-TrFE thin films were studied by FESEM, and the results of XRD and FTIR showed that the β-phase of PVDF-TrFE thin films was dominant. Meanwhile, the effects of different heating conditions on the crystallization and piezoelectric properties of PVDF-TrFE films were also studied. The flexible ME heterojunction composite has a significant ME voltage coefficient and excellent piezoelectric properties at room temperature, which allows it to be a candidate material for developing flexible magnetoelectric devices. Full article

(This article belongs to the Special Issue Feature Papers in Physical Chemistry and Chemical Physics 2022)

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16 pages, 3653 KiB

Open AccessArticle

Solubility Enhancement of Dihydroquercetin via “Green” Phase Modification

by Roman P. Terekhov, Igor R. Ilyasov, Vladimir L. Beloborodov, Anastasiya K. Zhevlakova, Denis I. Pankov, Alexander V. Dzuban, Anatoliy G. Bogdanov, Georgiy N. Davidovich, Gennadii V. Shilov, Andrey N. Utenyshev, Evgenya A. Saverina and Irina A. Selivanova

Int. J. Mol. Sci. 2022, 23(24), 15965; https://doi.org/10.3390/ijms232415965 - 15 Dec 2022

Cited by 4 | Viewed by 2538

Abstract

Dihydroquercetin (DHQ) is a promising antioxidant for medical applications. The poor water solubility of this flavanonol at ambient conditions inhibits its implementation in clinical practice as an injectable dosage form. Thus, increasing water solubility is a critical step toward solving this problem. Herein [...] Read more.

Dihydroquercetin (DHQ) is a promising antioxidant for medical applications. The poor water solubility of this flavanonol at ambient conditions inhibits its implementation in clinical practice as an injectable dosage form. Thus, increasing water solubility is a critical step toward solving this problem. Herein we attempted to deal with this problem via DHQ phase modification while at the same time adhering to the principles of green chemistry as much as possible. Lyophilization is an appropriate method to achieve phase modification in an environment-friendly way. This method was employed to generate new phase modifications of DHQ that were then characterized. Mixtures of water with ethanol or acetonitrile were used as solvents for the preparation of the lyophilizates, DHQ_E, and DHQ_A, respectively. The results of dissolution testing of the obtained DHQ_E and DHQ_A demonstrated that the lyophilization increased water solubility at least 30-fold times. These new DHQ modifications were studied by scanning electron microscopy, mass-spectrometry, nuclear magnetic resonance spectroscopy, infrared spectroscopy, X-ray powder diffraction, and thermal analysis. Their solid-state phases were confirmed to differ from the initial DHQ substance without any changes in the molecular structure. Both DHQ_E and DHQ_A showed as high antioxidant activity as the initial DHQ. These data demonstrate the potential of DHQ_E and DHQ_A as active pharmaceutical ingredients for injectable dosage forms. Full article

(This article belongs to the Special Issue Feature Papers in Physical Chemistry and Chemical Physics 2022)

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14 pages, 4103 KiB

Open AccessArticle

Crystallization Pathways of FABr-PbBr₂-DMF and FABr-PbBr₂-DMSO Systems: The Comprehensive Picture of Formamidinium-Based Low-Dimensional Perovskite-Related Phases and Intermediate Solvates

by Sergey A. Fateev, Ekaterina I. Marchenko, Alexandra S. Shatilova, Victor N. Khrustalev, Eugene A. Goodilin and Alexey B. Tarasov

Int. J. Mol. Sci. 2022, 23(23), 15344; https://doi.org/10.3390/ijms232315344 - 5 Dec 2022

Cited by 5 | Viewed by 3002

Abstract

In this study, we systematically investigated the phase diversity and crystallization pathways of the FABr excessive regions of two ternary systems of FABr-PbBr₂-DMF and FABr-PbBr₂-DMSO (where FA⁺—formamidinium cations, DMF—dimethylformamide and DMSO—dimethyl sulfoxide solvents). In these systems, a [...] Read more.

In this study, we systematically investigated the phase diversity and crystallization pathways of the FABr excessive regions of two ternary systems of FABr-PbBr₂-DMF and FABr-PbBr₂-DMSO (where FA⁺—formamidinium cations, DMF—dimethylformamide and DMSO—dimethyl sulfoxide solvents). In these systems, a new FA₃PbBr₅ phase with a structure containing chains of vertex-connected PbBr₆ octahedra is discovered, and its crystal structure is refined. We experimentally assess fundamental information on differences in the mechanisms of crystallization process in FABr-PbBr₂-DMF and FABr-PbBr₂-DMSO systems and determine possible pathways of crystallization of hybrid perovskites. We show that intermediate solvate phases are not observed in the system with DMF solvent, while a number of crystalline solvates tend to form in the system with DMSO at various amounts of FABr excess. Full article

(This article belongs to the Special Issue Feature Papers in Physical Chemistry and Chemical Physics 2022)

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10 pages, 1948 KiB

Open AccessArticle

Structural Anomaly in Glasses: Molecular Dynamics Study of Organic Radical in Dibutylphthalate at Different Temperatures

by Dmitry V. Alimov, Mikhail Yu. Ivanov, Svetlana Pylaeva and Matvey V. Fedin

Int. J. Mol. Sci. 2022, 23(23), 14859; https://doi.org/10.3390/ijms232314859 - 28 Nov 2022

Viewed by 1441

Abstract

Understanding the heterogeneous nano/microscopic structures of various organic glasses is fundamental and necessary for many applications. Recently, unusual structural phenomena have been observed experimentally in various organic glasses near their glass transition temperatures (

T_{g}

), including dibutyl phthalate (DBP). In particular, [...] Read more.

Understanding the heterogeneous nano/microscopic structures of various organic glasses is fundamental and necessary for many applications. Recently, unusual structural phenomena have been observed experimentally in various organic glasses near their glass transition temperatures (

T_{g}

), including dibutyl phthalate (DBP). In particular, the librational motion of radical probe in the glass is progressively suppressed upon temperature increase. In this work, we report in-depth molecular dynamics studies of structural anomalies in DBP glass, that revealed insights into the general mechanism of these phenomena. In particular, we have evidenced that the two types of solvation within alkyl chains coexist, allowing only small-angle wobbling of the solute molecule (TEMPO radical), and another favouring large-angle rotations. The former solvation assumes constrained location of the solute near carboxyl groups of DBP, while the latter is coupled to the concerted movement of butyl chains. Remarkably, excellent qualitative and quantitative agreement with previous experimental results were obtained. As such, we are certain that the above-mentioned dynamic phenomena explain the intriguing structural anomalies observed in DBP and some other glasses in the vicinity of

T_{g}

. Full article

(This article belongs to the Special Issue Feature Papers in Physical Chemistry and Chemical Physics 2022)

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14 pages, 9105 KiB

Open AccessArticle

Finite Element Solution for Dynamic Mechanical Parameter Influence on Underwater Sound Absorption of Polyurethane-Based Composite

by Dexian Yin, Yue Liu, Yimin Wang, Yangyang Gao, Shikai Hu, Li Liu and Xiuying Zhao

Int. J. Mol. Sci. 2022, 23(23), 14760; https://doi.org/10.3390/ijms232314760 - 25 Nov 2022

Cited by 5 | Viewed by 1751

Abstract

Underwater noise pollution, mainly emitted by shipping and ocean infrastructure development of human activities, has produced severe environmental impacts on marine species and seabed habitats. In recent years, a polyurethane-based (PU-based) composite with excellent damping performance has been increasingly utilized as underwater sound [...] Read more.

Underwater noise pollution, mainly emitted by shipping and ocean infrastructure development of human activities, has produced severe environmental impacts on marine species and seabed habitats. In recent years, a polyurethane-based (PU-based) composite with excellent damping performance has been increasingly utilized as underwater sound absorption material by attaching it to equipment surfaces. As one of the key parameters of damping materials, dynamic mechanical parameters are of vital importance to evaluating the viscoelastic damping property and thus influencing the sound absorption performance. Nevertheless, lots of researchers have not checked thoroughly the relationship and the mechanism of the material dynamic mechanical parameters and its sound absorption performance. In this work, a finite element model was fabricated and verified effectively using acoustic pulse tube tests to investigate the aforementioned issues. The influence of the dynamic mechanical parameters on underwater sound absorption performance was systematically studied with the frequency domain to reveal the mechanism and the relationship between damping properties and the sound absorption of the PU-based composite. The results indicate that the internal friction of the molecular segments and the structure stiffness were the two main contributors of the PU-based composite’s consumption of sound energy, and the sound absorption peak and the sound absorption coefficient could be clearly changed by adjusting the dynamic mechanical parameters of the composite. This study will provide helpful guidance to develop the fabrication and engineering applications of the PU-based composite with outstanding underwater sound absorption performance. Full article

(This article belongs to the Special Issue Feature Papers in Physical Chemistry and Chemical Physics 2022)

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14 pages, 14860 KiB

Open AccessArticle

Theoretical Evaluation of Sulfur-Based Reactions as a Model for Biological Antioxidant Defense

by Maria Laura De Sciscio, Valeria D’Annibale and Marco D’Abramo

Int. J. Mol. Sci. 2022, 23(23), 14515; https://doi.org/10.3390/ijms232314515 - 22 Nov 2022

Cited by 7 | Viewed by 1882

Abstract

Sulfur-containing amino acids, Methionine (Met) and Cysteine (Cys), are very susceptible to Reactive Oxygen Species (ROS). Therefore, sulfur-based reactions regulate many biological processes, playing a key role in maintaining cellular redox homeostasis and modulating intracellular signaling cascades. In oxidative conditions, Met acts as [...] Read more.

Sulfur-containing amino acids, Methionine (Met) and Cysteine (Cys), are very susceptible to Reactive Oxygen Species (ROS). Therefore, sulfur-based reactions regulate many biological processes, playing a key role in maintaining cellular redox homeostasis and modulating intracellular signaling cascades. In oxidative conditions, Met acts as a ROS scavenger, through Met sulfoxide formation, while thiol/disulfide interchange reactions take place between Cys residues as a response to many environmental stimuli. In this work, we apply a QM/MM theoretical–computational approach, which combines quantum–mechanical calculations with classical molecular dynamics simulations to estimate the free energy profile for the above-mentioned reactions in solution. The results obtained, in good agreement with experimental data, show the validity of our approach in modeling sulfur-based reactions, enabling us to study these mechanisms in more complex biological systems. Full article

(This article belongs to the Special Issue Feature Papers in Physical Chemistry and Chemical Physics 2022)

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20 pages, 2774 KiB

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Mechanism of Phase Separation in Aqueous Two-Phase Systems

by Amber R. Titus, Pedro P. Madeira, Luisa A. Ferreira, Vladimir Y. Chernyak, Vladimir N. Uversky and Boris Y. Zaslavsky

Int. J. Mol. Sci. 2022, 23(22), 14366; https://doi.org/10.3390/ijms232214366 - 19 Nov 2022

Cited by 17 | Viewed by 3342

Abstract

Liquid-liquid phase separation underlies the formation of membrane-less organelles inside living cells. The mechanism of this process can be examined using simple aqueous mixtures of two or more solutes, which are able to phase separate at specific concentration thresholds. This work presents the [...] Read more.

Liquid-liquid phase separation underlies the formation of membrane-less organelles inside living cells. The mechanism of this process can be examined using simple aqueous mixtures of two or more solutes, which are able to phase separate at specific concentration thresholds. This work presents the first experimental evidence that mesoscopic changes precede visually detected macroscopic phase separation in aqueous mixtures of two polymers and a single polymer and salt. Dynamic light scattering (DLS) analysis indicates the formation of mesoscopic polymer agglomerates in these systems. These agglomerates increase in size with increasing polymer concentrations prior to visual phase separation. Such mesoscopic changes are paralleled by changes in water structure as evidenced by Attenuated Total Reflection—Fourier Transform Infrared (ATR-FTIR) spectroscopic analysis of OH-stretch bands. Through OH-stretch band analysis, we obtain quantitative estimates of the relative fractions of four subpopulations of water structures coexisting in aqueous solutions. These estimates indicate that abrupt changes in hydrogen bond arrangement take place at concentrations below the threshold of macroscopic phase separation. We used these experimental observations to develop a model of phase separation in aqueous media. Full article

(This article belongs to the Special Issue Feature Papers in Physical Chemistry and Chemical Physics 2022)

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19 pages, 5315 KiB

Open AccessArticle

Surface Protection of Quaternary Gold Alloys by Thiol Self-Assembled Monolayers

by Guadalupe Sánchez-Obrero, Irene Humanes, Rafael Madueño, José Manuel Sevilla, Teresa Pineda and Manuel Blázquez

Int. J. Mol. Sci. 2022, 23(22), 14132; https://doi.org/10.3390/ijms232214132 - 16 Nov 2022

Cited by 2 | Viewed by 2490

Abstract

This work deals with a physical and chemical surface characterization of quaternary 18K, 14K, and 9K gold alloys and pure polycrystalline gold substrates. Surface microstructure and composition are evaluated by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and X-ray fluorescence spectroscopy. Corrosion [...] Read more.

This work deals with a physical and chemical surface characterization of quaternary 18K, 14K, and 9K gold alloys and pure polycrystalline gold substrates. Surface microstructure and composition are evaluated by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and X-ray fluorescence spectroscopy. Corrosion resistance of 18K gold alloys is explored by potentiodynamic polarization showing the influence of the manufacturing process on materials fabricated as plates and wires. The research is also in the framework of one of the most common strategies on the modification of metallic surface properties, i.e., the building of self-assembled monolayers (SAM) from organic thiols. The metal affinity of the head group to produce the coating of the substrate by covalent binding is approached by using thiol compounds with different molecular structures and functional group chemistries exposed to an electrolyte solution. Therefore, a comparative study on the surface protection of a quaternary 18K gold alloy and pure gold substrates by SAMs of 6-mercaptopurine (6MP), 1-decanethiol (DT), and 11-mercaptoundecanoic acid (MUA) has been carried out. Surface modification and SAM organization are followed by cyclic voltammetry (CV), and the behavior of the double layer of the electrode–electrolyte interface is evaluated by electrochemical impedance spectroscopy (EIS). The study of these materials allows us to extract fundamental knowledge for its potential application in improving the bioactive properties of different jewelry pieces based on 18K gold alloys. Full article

(This article belongs to the Special Issue Feature Papers in Physical Chemistry and Chemical Physics 2022)

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16 pages, 2431 KiB

Open AccessArticle

Diffusiophoresis of a Nonionic Micelle in Salt Gradients; Roles of Preferential Hydration and Salt-Induced Surfactant Aggregation

by Eliandreina Cruz Barrios, Kyra V. Penino and Onofrio Annunziata

Int. J. Mol. Sci. 2022, 23(22), 13710; https://doi.org/10.3390/ijms232213710 - 8 Nov 2022

Cited by 5 | Viewed by 2035

Abstract

Diffusiophoresis is the migration of a colloidal particle in water driven by concentration gradients of cosolutes such as salts. We have experimentally characterized the diffusiophoresis of tyloxapol micelles in the presence of MgSO₄, a strong salting-out agent. Specifically, we determined the [...] Read more.

Diffusiophoresis is the migration of a colloidal particle in water driven by concentration gradients of cosolutes such as salts. We have experimentally characterized the diffusiophoresis of tyloxapol micelles in the presence of MgSO₄, a strong salting-out agent. Specifically, we determined the multicomponent-diffusion coefficients using Rayleigh interferometry, cloud points, and dynamic-light-scattering diffusion coefficients on the ternary tyloxapol–MgSO₄–water system at 25 °C. Our experimental results show that micelle diffusiophoresis occurs from a high to a low salt concentration (positive diffusiophoresis). Moreover, our data were used to characterize the effect of salt concentration on micelle size and salt osmotic diffusion, which occurs from a high to a low surfactant concentration. Although micelle diffusiophoresis can be attributed to the preferential hydration of the polyethylene glycol surface groups, salting-out salts also promote an increase in the size of micellar aggregates, ultimately leading to phase separation at high salt concentration. This complicates diffusiophoresis description, as it is not clear how salt-induced surfactant aggregation contributes to micelle diffusiophoresis. We, therefore, developed a two-state aggregation model that successfully describes the observed effect of salt concentration on the size of tyloxapol micelles, in the case of MgSO₄ and the previously reported case of Na₂SO₄. Our model was then used to theoretically evaluate the contribution of salt-induced aggregation to diffusiophoresis. Our analysis indicates that salt-induced aggregation promotes micelle diffusiophoresis from a low to a high salt concentration (negative diffusiophoresis). However, we also determined that this mechanism marginally contributes to overall diffusiophoresis, implying that preferential hydration is the main mechanism causing micelle diffusiophoresis. Our results suggest that sulfate salts may be exploited to induce the diffusiophoresis of PEG-functionalized particles such as micelles, with potential applications to microfluidics, enhanced oil recovery, and controlled-release technologies. Full article

(This article belongs to the Special Issue Feature Papers in Physical Chemistry and Chemical Physics 2022)

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17 pages, 2631 KiB

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High-Mobility Naphthalene Diimide Derivatives Revealed by Raman-Based In Silico Screening

by Mikhail V. Vener, Oleg G. Kharlanov and Andrey Yu. Sosorev

Int. J. Mol. Sci. 2022, 23(21), 13305; https://doi.org/10.3390/ijms232113305 - 1 Nov 2022

Cited by 4 | Viewed by 2033

Abstract

Charge transport in crystalline organic semiconductors (OSCs) is considerably hindered by low-frequency vibrations introducing dynamic disorder in the charge transfer integrals. Recently, we have shown that the contributions of various vibrational modes to the dynamic disorder correlate with their Raman intensities and suggested [...] Read more.

Charge transport in crystalline organic semiconductors (OSCs) is considerably hindered by low-frequency vibrations introducing dynamic disorder in the charge transfer integrals. Recently, we have shown that the contributions of various vibrational modes to the dynamic disorder correlate with their Raman intensities and suggested a Raman-based approach for estimation of the dynamic disorder and search for potentially high-mobility OSCs. In the present paper, we showcase this approach by revealing the highest-mobility OSC(s) in two series of crystalline naphthalene diimide derivatives bearing alkyl or cycloalkyl substituents. In contrast to our previous studies, Raman spectra are not measured, but are instead calculated using periodic DFT. As a result, an OSC with a potentially high charge mobility is revealed in each of the two series, and further mobility calculations corroborate this choice. Namely, for the naphthalene diimide derivatives with butyl and cyclopentyl substituents, the estimated room-temperature isotropic electron mobilities are as high as 6 and 15 cm² V^–1 s^–1, respectively, in the latter case even exceeding 20 cm² V^–1 s^–1 in a two-dimensional plane. Thus, our results highlight the potential of using the calculated Raman spectra to search for high-mobility crystalline OSCs and reveal two promising OSCs, which were previously overlooked. Full article

(This article belongs to the Special Issue Feature Papers in Physical Chemistry and Chemical Physics 2022)

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9 pages, 3082 KiB

Open AccessArticle

Enhanced Resistive Switching and Synaptic Characteristics of ALD Deposited AlN-Based RRAM by Positive Soft Breakdown Process

by Seyeong Yang, Jongmin Park, Youngboo Cho, Yunseok Lee and Sungjun Kim

Int. J. Mol. Sci. 2022, 23(21), 13249; https://doi.org/10.3390/ijms232113249 - 31 Oct 2022

Cited by 10 | Viewed by 2117

Abstract

Nitride film played an essential role as an excellent diffusion barrier in the semiconductor field for several decades. In addition, interest in next-generation memories induced researchers’ attention to nitride film as a new storage medium. A Pt/AlN/TaN device was investigated for resistive random-access [...] Read more.

Nitride film played an essential role as an excellent diffusion barrier in the semiconductor field for several decades. In addition, interest in next-generation memories induced researchers’ attention to nitride film as a new storage medium. A Pt/AlN/TaN device was investigated for resistive random-access memory (RRAM) application in this work. Resistive switching properties were examined in the AlN thin film formed by atomic layer deposition (ALD). The unique switching feature conducted under the positive voltage was investigated, while the typical bipolar switching was conducted under the application of negative voltage. Good retention and DC, and pulse endurances were achieved in both conditions and compared to the memory performances. Finally, the electronic behaviors based on the unique switching feature were analyzed through X-ray photoelectron spectroscopy (XPS) and the current–voltage (I–V) linear fitting model. Full article

(This article belongs to the Special Issue Feature Papers in Physical Chemistry and Chemical Physics 2022)

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26 pages, 4395 KiB

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CADMA-Chem: A Computational Protocol Based on Chemical Properties Aimed to Design Multifunctional Antioxidants

by Eduardo Gabriel Guzman-Lopez, Miguel Reina, Adriana Perez-Gonzalez, Misaela Francisco-Marquez, Luis Felipe Hernandez-Ayala, Romina Castañeda-Arriaga and Annia Galano

Int. J. Mol. Sci. 2022, 23(21), 13246; https://doi.org/10.3390/ijms232113246 - 31 Oct 2022

Cited by 9 | Viewed by 3092

Abstract

A computational protocol aimed to design new antioxidants with versatile behavior is presented. It is called Computer-Assisted Design of Multifunctional Antioxidants and is based on chemical properties (CADMA-Chem). The desired multi-functionality consists of in different methods of antioxidant protection combined with neuroprotection, although [...] Read more.

A computational protocol aimed to design new antioxidants with versatile behavior is presented. It is called Computer-Assisted Design of Multifunctional Antioxidants and is based on chemical properties (CADMA-Chem). The desired multi-functionality consists of in different methods of antioxidant protection combined with neuroprotection, although the protocol can also be used to pursue other health benefits. The dM38 melatonin derivative is used as a study case to illustrate the protocol in detail. This was found to be a highly promising candidate for the treatment of neurodegeneration, in particular Parkinson’s and Alzheimer’s diseases. This also has the desired properties of an oral-drug, which is significantly better than Trolox for scavenging free radicals, and has chelates redox metals, prevents the ^●OH production, via Fenton-like reactions, repairs oxidative damage in biomolecules (lipids, proteins, and DNA), and acts as a polygenic neuroprotector by inhibiting catechol-O-methyl transferase (COMT), acetylcholinesterase (AChE) and monoamine oxidase B (MAOB). To the best of our best knowledge, CADMA-Chem is currently the only protocol that simultaneously involves the analyses of drug-like behavior, toxicity, manufacturability, versatile antioxidant protection, and receptor–ligand binding affinities. It is expected to provide a starting point that helps to accelerate the discovery of oral drugs with the potential to prevent, or slow down, multifactorial human health disorders. Full article

(This article belongs to the Special Issue Feature Papers in Physical Chemistry and Chemical Physics 2022)

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16 pages, 1398 KiB

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Research of a Thermodynamic Function

{(\frac{\partial p}{\partial x})}_{T, x \to 0}

: Temperature Dependence and Relation to Properties at Infinite Dilution

by Jiahuan Zheng, Xia Chen, Yan Wang, Qichao Sun, Wenting Sun, Lianying Wu, Yangdong Hu and Weitao Zhang

Int. J. Mol. Sci. 2022, 23(21), 12998; https://doi.org/10.3390/ijms232112998 - 27 Oct 2022

Cited by 1 | Viewed by 1391

Abstract

In this work, we propose the idea of considering

{(\frac{\partial p}{\partial x})}_{T, x \to 0}

as an infinite dilution thermodynamic function. Our research shows that

{(\frac{\partial p}{\partial x})}_{T, x \to 0}

as [...] Read more.

In this work, we propose the idea of considering

{(\frac{\partial p}{\partial x})}_{T, x \to 0}

as an infinite dilution thermodynamic function. Our research shows that

{(\frac{\partial p}{\partial x})}_{T, x \to 0}

as a thermodynamic function is closely related to temperature, with the relation being simply expressed as:

\ln {(\frac{\partial p}{\partial x})}_{T, x \to 0} = \frac{A}{T} + B

. Then, we use this equation to correlate the isothermal vapor–liquid equilibrium (VLE) data for 40 systems. The result shows that the total average relative deviation is 0.15%, and the total average absolute deviation is 3.12%. It indicates that the model correlates well with the experimental data. Moreover, we start from the total pressure expression, and use the Gibbs–Duhem equation to re-derive the relationship between

{(\frac{\partial p}{\partial x})}_{T, x \to 0}

and the infinite dilution activity coefficient (

γ^{\infty}

) at low pressure. Based on the definition of partial molar volume, an equation for

{(\frac{\partial p}{\partial x})}_{T, x \to 0}

and gas solubility at high pressure is proposed in our work. Then, we use this equation to correlate the literature data on the solubility of nitrogen, hydrogen, methane, and carbon dioxide in water. These systems are reported at temperatures ranging from 273.15 K to 398.15 K and pressures up to 101.325 MPa. The total average relative deviation of the predicted values with respect to the experimental data is 0.08%, and the total average absolute deviation is 2.68%. Compared with the Krichevsky–Kasarnovsky equation, the developed model provides more reliable results. Full article

(This article belongs to the Special Issue Feature Papers in Physical Chemistry and Chemical Physics 2022)

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25 pages, 1251 KiB

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The Mayo Clinic Florida Microdosimetric Kinetic Model of Clonogenic Survival: Application to Various Repair-Competent Rodent and Human Cell Lines

by Alessio Parisi, Chris J. Beltran and Keith M. Furutani

Int. J. Mol. Sci. 2022, 23(20), 12491; https://doi.org/10.3390/ijms232012491 - 18 Oct 2022

Cited by 11 | Viewed by 1590

Abstract

The relative biological effectiveness (RBE) calculations used during the planning of ion therapy treatments are generally based on the microdosimetric kinetic model (MKM) and the local effect model (LEM). The Mayo Clinic Florida MKM (MCF MKM) was recently developed to overcome the limitations [...] Read more.

The relative biological effectiveness (RBE) calculations used during the planning of ion therapy treatments are generally based on the microdosimetric kinetic model (MKM) and the local effect model (LEM). The Mayo Clinic Florida MKM (MCF MKM) was recently developed to overcome the limitations of previous MKMs in reproducing the biological data and to eliminate the need for ion-exposed in vitro data as input for the model calculations. Since we are considering to implement the MCF MKM in clinic, this article presents (a) an extensive benchmark of the MCF MKM predictions against corresponding in vitro clonogenic survival data for 4 rodent and 10 cell lines exposed to ions from ¹H to ²³⁸U, and (b) a systematic comparison with published results of the latest version of the LEM (LEM IV). Additionally, we introduce a novel approach to derive an approximate value of the MCF MKM model parameters by knowing only the animal species and the mean number of chromosomes. The overall good agreement between MCF MKM predictions and in vitro data suggests the MCF MKM can be reliably used for the RBE calculations. In most cases, a reasonable agreement was found between the MCF MKM and the LEM IV. Full article

(This article belongs to the Special Issue Feature Papers in Physical Chemistry and Chemical Physics 2022)

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13 pages, 2265 KiB

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Aquacobalamin Accelerates Orange II Destruction by Peroxymonosulfate via the Transient Formation of Secocorrinoid: A Mechanistic Study

by Ilia A. Dereven’kov, Ekaterina S. Sakharova, Vladimir S. Osokin and Sergei V. Makarov

Int. J. Mol. Sci. 2022, 23(19), 11907; https://doi.org/10.3390/ijms231911907 - 7 Oct 2022

Cited by 3 | Viewed by 1737

Abstract

Besides its use in medicine, vitamin B₁₂ (cobalamin) and its derivatives have found in numerous applications as catalysts. However, studies related to the activation of oxidants via cobalamin are scant. In this work, we showed how the addition of aquacobalamin (H₂ [...] Read more.

Besides its use in medicine, vitamin B₁₂ (cobalamin) and its derivatives have found in numerous applications as catalysts. However, studies related to the activation of oxidants via cobalamin are scant. In this work, we showed how the addition of aquacobalamin (H₂OCbl) accelerates the destruction of azo-dye Orange II by peroxymonosulfate (HSO₅⁻) in aqueous solutions. In neutral and weakly alkaline media, the process is initiated by the modification of the corrin macrocycle with HSO₅⁻, which requires the preliminary deprotonation of the aqua-ligand in H₂OCbl to give hydroxocobalamin, producing 5,6-dioxo-5,6-secocobalamin or its isomer (14,15-dioxo-14,15-secocobalamin). In acidic solutions, where the concentration of hydroxocobalamin is negligible, the formation of dioxo-seco-species is not observed, and the reaction between H₂OCbl and HSO₅⁻ results in slow chromophore bleaching. Using terephthalic acid, we demonstrated the formation of hydroxyl radicals in the mixture of H₂OCbl with HSO₅⁻, whereas the generation of sulfate radicals was proved by comparing the effects of ethanol and nitrobenzene on Orange II destruction using the H₂OCbl/HSO₅⁻ system. The reaction mechanism includes the binding of HSO₅⁻ to the Co(III) ion of dioxo-secocobalamin, which results in its deprotonation and the labilization of the O-O bond, leading to the formation of sulfate and hydroxyl radicals which further react with Orange II. Full article

(This article belongs to the Special Issue Feature Papers in Physical Chemistry and Chemical Physics 2022)

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23 pages, 4235 KiB

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Semi-Empirical Calculation of Bodipy Aggregate Spectroscopic Properties through Direct Sampling of Configurational Ensembles

by Sergey Usoltsev, Artem Shagurin and Yuriy Marfin

Int. J. Mol. Sci. 2022, 23(18), 10955; https://doi.org/10.3390/ijms231810955 - 19 Sep 2022

Cited by 2 | Viewed by 1923

Abstract

Efficient prediction of the aggregation-induced callback of organic chromophores for utilization in molecular sensorics is a desirable development goal in modern computational chemistry. Dye aggregates are complicated to study when utilizing conventional quantum chemistry approaches, since they are usually composed of too many [...] Read more.

Efficient prediction of the aggregation-induced callback of organic chromophores for utilization in molecular sensorics is a desirable development goal in modern computational chemistry. Dye aggregates are complicated to study when utilizing conventional quantum chemistry approaches, since they are usually composed of too many atoms to be effectively analyzed, even with high-throughput parallel systems. Here, we present a successful attempt to develop a protocol to assess the spectroscopic changes happening in BODIPY dyes upon aggregation from the first principles utilizing extended tight-binding (XTB) and Zerner’s intermediate neglect of differential overlap (ZINDO) Hamiltonians. The developed sampling technique for aggregate configurational space scanning was found to be sufficient to both reproduce peculiarities and justify experimental data on the spectroscopic behavior of chromophore aggregates. The sTDA, sTD-DFT (GFN2-XTB) and CIS (ZINDO) approaches were assessed, and then sources of errors and benefits were outlined. Importantly, our goal was to keep any of the mentioned calculations within a computational cost feasible for a single workstation, whereas scaling was possible at any point in time. Finally, several aggregate structures were investigated in the external field to try to achieve distributions similar to the ones observed in the electrostatic potential of the air–water interface to assess the borderlines of practical applicability of the suggested scheme. Full article

(This article belongs to the Special Issue Feature Papers in Physical Chemistry and Chemical Physics 2022)

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9 pages, 2483 KiB

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Sensing Leakage of Electrolytes from Magnesium Batteries Enabled by Natural AIEgens

by Yingxiang Zhai, Jiguo Zhang, Jian Li, Shouxin Liu, Zhijun Chen and Shujun Li

Int. J. Mol. Sci. 2022, 23(18), 10440; https://doi.org/10.3390/ijms231810440 - 9 Sep 2022

Viewed by 1665

Abstract

The potential for leakage of liquid electrolytes from magnesium (Mg) batteries represents a large hurdle to future application. Despite this, there are no efficient sensing technologies to detect the leakage of liquid electrolytes. Here, we developed a sensor using laccaic acid (L-AIEgen), a [...] Read more.

The potential for leakage of liquid electrolytes from magnesium (Mg) batteries represents a large hurdle to future application. Despite this, there are no efficient sensing technologies to detect the leakage of liquid electrolytes. Here, we developed a sensor using laccaic acid (L-AIEgen), a naturally occurring aggregation-induced emission luminogen (AIEgens) isolated from the beetle Laccifer lacca. L-AIEgen showed good selectivity and sensitivity for Mg²⁺, a universal component of electrolytes in Mg batteries. Using L-AIEgen, we then produced a smart film (L-AIE-F) that was able to sense leakage of electrolytes from Mg batteries. L-AIE-F showed a strong “turn-on” AIE-active fluorescence at the leakage point of electrolyte from model Mg batteries. To the best of our knowledge, this is the first time that AIE technology has been used to sense the leakage of electrolytes. Full article

(This article belongs to the Special Issue Feature Papers in Physical Chemistry and Chemical Physics 2022)

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12 pages, 4956 KiB

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Efficient Adsorption-Photocatalytic Removal of Tetracycline Hydrochloride over Octahedral MnS

by Jing Guo, Tingting Liu, Hao Peng and Xiaogang Zheng

Int. J. Mol. Sci. 2022, 23(16), 9343; https://doi.org/10.3390/ijms23169343 - 19 Aug 2022

Cited by 8 | Viewed by 1903

Abstract

To disclose the effect of crystal plane on the adsorption-photocatalytic activity of MnS, octahedral MnS was prepared via the hydrothermal route to enhance the adsorption and photocatalytic efficiencies of tetracycline hydrochloride (TCH) in visible light region. The optimal MnS treated at 433 K [...] Read more.

To disclose the effect of crystal plane on the adsorption-photocatalytic activity of MnS, octahedral MnS was prepared via the hydrothermal route to enhance the adsorption and photocatalytic efficiencies of tetracycline hydrochloride (TCH) in visible light region. The optimal MnS treated at 433 K for 16 h could remove 94.83% TCH solution of 260 mg L⁻¹ within 180 min, and its adsorption-photocatalytic efficiency declined to 89.68% after five cycles. Its excellent adsorption-photocatalytic activity and durability were ascribed to the sufficient vacant sites of octahedral structure for TCH adsorption and the feasible band-gap structure for visible-light response. In addition, the band gap structure (1.37 eV) of MnS with a conduction band value of −0.58 eV and a valence band value of 0.79 eV was favorable for the generation of O²⁻, while unsuitable for the formation of OH. Hence, octahedral MnS was a potential material for the removal of antibiotics from wastewater. Full article

(This article belongs to the Special Issue Feature Papers in Physical Chemistry and Chemical Physics 2022)

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15 pages, 9467 KiB

Open AccessArticle

Synthesis of Tin-Doped Three-Dimensional Flower-like Bismuth Tungstate with Enhanced Photocatalytic Activity

by Xiaodong Zhu, Fengqiu Qin, Xiuping Zhang, Yuanyuan Zhong, Juan Wang, Yu Jiao, Yuhao Luo and Wei Feng

Int. J. Mol. Sci. 2022, 23(15), 8422; https://doi.org/10.3390/ijms23158422 - 29 Jul 2022

Cited by 16 | Viewed by 2147

Abstract

Photocatalytic degradation of harmful organic matter is a feasible and environmentally friendly method. Bi₂WO₆ has become a hotspot of photocatalysts because of its unique layered structure and visible light response. In the present study, Sn doping was adopted to modified [...] Read more.

Photocatalytic degradation of harmful organic matter is a feasible and environmentally friendly method. Bi₂WO₆ has become a hotspot of photocatalysts because of its unique layered structure and visible light response. In the present study, Sn doping was adopted to modified Bi₂WO₆ by hydrothermal method. The Sn-doped Bi₂WO₆ photocatalysts were characterized by XRD, SEM, TEM, BET, XPS, PL, and DRS, respectively. The results show that Sn-doped Bi₂WO₆ shows three-dimensional (3D) flower-like morphology, which is composed of two-dimensional (2D) nanosheets. Sn⁴⁺ ions enter into the Bi₂WO₆ lattice, producing a degree of Bi₂WO₆ lattice distortion, which is in favor of reducing the recombination of photogenerated electrons and holes. Moreover, the specific surface area of Bi₂WO₆ is significantly increased after doping, which is beneficial to providing more active sites. The photocatalytic results show that 2%Sn-Bi₂WO₆ exhibits the highest photocatalytic activity. After 60 min of irradiation, the photocatalytic degradation degree of methylene blue (MB) increases from 80.6% for pure Bi₂WO₆ to 92.0% for 2%Sn-Bi₂WO₆. The first-order reaction rate constant of 2%Sn-Bi₂WO₆ is 0.030 min⁻¹, which is 1.7 times than that of pure Bi₂WO₆. Full article

(This article belongs to the Special Issue Feature Papers in Physical Chemistry and Chemical Physics 2022)

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13 pages, 5148 KiB

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Cuprous Oxide Thin Films Implanted with Chromium Ions—Optical and Physical Properties Studies

by Katarzyna Ungeheuer, Konstanty W. Marszalek, Marzena Mitura-Nowak, Piotr Jelen, Marcin Perzanowski, Marta Marszalek and Maciej Sitarz

Int. J. Mol. Sci. 2022, 23(15), 8358; https://doi.org/10.3390/ijms23158358 - 28 Jul 2022

Cited by 5 | Viewed by 2329

Abstract

Cuprous oxide is a semiconductor with potential for use in photocatalysis, sensors, and photovoltaics. We used ion implantation to modify the properties of Cu₂O oxide. Thin films of Cu₂O were deposited with magnetron sputtering and implanted with low-energy Cr [...] Read more.

Cuprous oxide is a semiconductor with potential for use in photocatalysis, sensors, and photovoltaics. We used ion implantation to modify the properties of Cu₂O oxide. Thin films of Cu₂O were deposited with magnetron sputtering and implanted with low-energy Cr ions of different dosages. The X-ray diffraction method was used to determine the structure and composition of deposited and implanted films. The optical properties of the material before and after implantation were studied using spectrophotometry and spectroscopic ellipsometry. The investigation of surface topography was performed with atomic force microscopy. The implantation had little influence on the atomic lattice constant of the oxide structure, and no clear dependence of microstrain or crystalline size on the dose of implantation was found. The appearance of phase change was observed, which could have been caused by the implantation. Ellipsometry measurements showed an increase in the total thickness of the sample with an increase in the amount of implanted Cr ions, which indicates the influence of implantation on the properties of the surface and subsurface region. The refractive index n, extinction coefficient k, and absorption coefficient optical parameters show different energy dependences related to implantation dose. Full article

(This article belongs to the Special Issue Feature Papers in Physical Chemistry and Chemical Physics 2022)

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14 pages, 5308 KiB

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Enhanced Photoluminescence and Electrical Properties of n-Al-Doped ZnO Nanorods/p-B-Doped Diamond Heterojunction

by Yu Yao, Dandan Sang, Liangrui Zou, Dong Zhang, Qingru Wang, Xueting Wang, Liying Wang, Jie Yin, Jianchao Fan and Qinglin Wang

Int. J. Mol. Sci. 2022, 23(7), 3831; https://doi.org/10.3390/ijms23073831 - 30 Mar 2022

Cited by 8 | Viewed by 2867

Abstract

The hydrothermal approach has been used to fabricate a heterojunction of n-aluminum-doped ZnO nanorods/p-B-doped diamond (n-Al:ZnO NRs/p-BDD). It exhibits a significant increase in photoluminescence (PL) intensity and a blue shift of the UV emission peak when compared to the n-ZnO NRs/p-BDD heterojunction. The [...] Read more.

The hydrothermal approach has been used to fabricate a heterojunction of n-aluminum-doped ZnO nanorods/p-B-doped diamond (n-Al:ZnO NRs/p-BDD). It exhibits a significant increase in photoluminescence (PL) intensity and a blue shift of the UV emission peak when compared to the n-ZnO NRs/p-BDD heterojunction. The current voltage (I-V) characteristics exhibit excellent rectifying behavior with a high rectification ratio of 838 at 5 V. The n-Al:ZnO NRs/p-BDD heterojunction shows a minimum turn-on voltage (0.27 V) and reverse leakage current (0.077 μA). The forward current of the n-Al:ZnO NRs/p-BDD heterojunction is more than 1300 times than that of the n-ZnO NRs/p-BDD heterojunction at 5 V. The ideality factor and the barrier height of the Al-doped device were found to decrease. The electrical transport behavior and carrier injection process of the n-Al:ZnO NRs/p-BDD heterojunction were analyzed through the equilibrium energy band diagrams and semiconductor theoretical models. Full article

(This article belongs to the Special Issue Feature Papers in Physical Chemistry and Chemical Physics 2022)

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16 pages, 1967 KiB

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Physicochemical and Theoretical Characterization of a New Small Non-Metal Schiff Base with a Differential Antimicrobial Effect against Gram-Positive Bacteria

by Manuel Gacitúa, Alexander Carreño, Rosaly Morales-Guevara, Dayán Páez-Hernández, Jorge I. Martínez-Araya, Eyleen Araya, Marcelo Preite, Carolina Otero, María Macarena Rivera-Zaldívar, Andrés Silva and Juan A. Fuentes

Int. J. Mol. Sci. 2022, 23(5), 2553; https://doi.org/10.3390/ijms23052553 - 25 Feb 2022

Cited by 6 | Viewed by 3292

Abstract

Searching for adequate and effective compounds displaying antimicrobial activities, especially against Gram-positive bacteria, is an important research area due to the high hospitalization and mortality rates of these bacterial infections in both the human and veterinary fields. In this work, we explored ( [...] Read more.

Searching for adequate and effective compounds displaying antimicrobial activities, especially against Gram-positive bacteria, is an important research area due to the high hospitalization and mortality rates of these bacterial infections in both the human and veterinary fields. In this work, we explored (E)-4-amino-3-((3,5-di-tert-butyl-2-hydroxybenzylidene)amino) benzoic acid (SB-1, harboring an intramolecular hydrogen bond) and (E)-2-((4-nitrobenzilidene)amino)aniline (SB-2), two Schiff bases derivatives. Results demonstrated that SB-1 showed an antibacterial activity determined by the minimal inhibitory concentration (MIC) against Staphylococcus aureus, Enterococcus faecalis, and Bacillus cereus (Gram-positive bacteria involved in human and animal diseases such as skin infections, pneumonia, diarrheal syndrome, and urinary tract infections, among others), which was similar to that shown by the classical antibiotic chloramphenicol. By contrast, this compound showed no effect against Gram-negative bacteria (Klebsiella pneumoniae, Escherichia coli, and Salmonella enterica). Furthermore, we provide a comprehensive physicochemical and theoretical characterization of SB-1 (as well as several analyses for SB-2), including elemental analysis, ESMS, ¹H and ¹³C NMR (assigned by 1D and 2D techniques), DEPT, UV-Vis, FTIR, and cyclic voltammetry. We also performed a computational study through the DFT theory level, including geometry optimization, TD-DFT, NBO, and global and local reactivity analyses. Full article

(This article belongs to the Special Issue Feature Papers in Physical Chemistry and Chemical Physics 2022)

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24 pages, 2228 KiB

Open AccessArticle

Catalytic Sulfation of Betulin with Sulfamic Acid: Experiment and DFT Calculation

by Aleksandr S. Kazachenko, Feride Akman, Natalya Yu. Vasilieva, Noureddine Issaoui, Yuriy N. Malyar, Aleksandr A. Kondrasenko, Valentina S. Borovkova, Angelina V. Miroshnikova, Anna S. Kazachenko, Omar Al-Dossary, Marek J. Wojcik, Yaroslava D. Berezhnaya and Evgeniy V. Elsuf’ev

Int. J. Mol. Sci. 2022, 23(3), 1602; https://doi.org/10.3390/ijms23031602 - 29 Jan 2022

Cited by 13 | Viewed by 3289

Abstract

Betulin is an important triterpenoid substance isolated from birch bark, which, together with its sulfates, exhibits important bioactive properties. We report on a newly developed method of betulin sulfation with sulfamic acid in pyridine in the presence of an Amberlyst^®15 solid [...] Read more.

Betulin is an important triterpenoid substance isolated from birch bark, which, together with its sulfates, exhibits important bioactive properties. We report on a newly developed method of betulin sulfation with sulfamic acid in pyridine in the presence of an Amberlyst^®15 solid acid catalyst. It has been shown that this catalyst remains stable when being repeatedly (up to four cycles) used and ensures obtaining of sulfated betulin with a sulfur content of ~10%. The introduction of the sulfate group into the betulin molecule has been proven by Fourier-transform infrared, ultraviolet-visible, and nuclear magnetic resonance spectroscopy. The Fourier-transform infrared (FTIR) spectra contain absorption bands at 1249 and 835–841 cm⁻¹; in the UV spectra, the peak intensity decreases; and, in the nuclear magnetic resonance (NMR) spectra, of betulin disulfate, carbons С3 and С28 are completely shifted to the weak-field region (to 88.21 and 67.32 ppm, respectively) with respect to betulin. Using the potentiometric titration method, the product of acidity constants K₁ and K₂ of a solution of the betulin disulfate H⁺ form has been found to be 3.86 × 10^–6 ± 0.004. It has been demonstrated by the thermal analysis that betulin and the betulin disulfate sodium salt are stable at temperatures of up to 240 and 220 °C, respectively. The density functional theory method has been used to obtain data on the most stable conformations, molecular electrostatic potential, frontier molecular orbitals, and mulliken atomic charges of betulin and betulin disulfate and to calculate the spectral characteristics of initial and sulfated betulin, which agree well with the experimental data. Full article

(This article belongs to the Special Issue Feature Papers in Physical Chemistry and Chemical Physics 2022)

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16 pages, 1352 KiB

Open AccessArticle

Designing Red-Shifted Molecular Emitters Based on the Annulated Locked GFP Chromophore Derivatives

by Gregory D. Sinenko, Dilara A. Farkhutdinova, Ivan N. Myasnyanko, Nadezhda S. Baleeva, Mikhail S. Baranov and Anastasia V. Bochenkova

Int. J. Mol. Sci. 2021, 22(24), 13645; https://doi.org/10.3390/ijms222413645 - 20 Dec 2021

Cited by 5 | Viewed by 2539

Abstract

Bioimaging techniques require development of a wide variety of fluorescent probes that absorb and emit red light. One way to shift absorption and emission of a chromophore to longer wavelengths is to modify its chemical structure by adding polycyclic aromatic hydrocarbon (PAH) fragments, [...] Read more.

Bioimaging techniques require development of a wide variety of fluorescent probes that absorb and emit red light. One way to shift absorption and emission of a chromophore to longer wavelengths is to modify its chemical structure by adding polycyclic aromatic hydrocarbon (PAH) fragments, thus increasing the conjugation length of a molecule while maintaining its rigidity. Here, we consider four novel classes of conformationally locked Green Fluorescent Protein (GFP) chromophore derivatives obtained by extending their aromatic systems in different directions. Using high-level ab initio quantum chemistry calculations, we show that the alteration of their electronic structure upon annulation may unexpectedly result in a drastic change of their fluorescent properties. A flip of optically bright and dark electronic states is most prominent in the symmetric fluorene-based derivative. The presence of a completely dark lowest-lying excited state is supported by the experimentally measured extremely low fluorescence quantum yield of the newly synthesized compound. Importantly, one of the asymmetric modes of annulation provides a very promising strategy for developing red-shifted molecular emitters with an absorption wavelength of ∼600 nm, having no significant impact on the character of the bright S-S₁ transition. Full article

(This article belongs to the Special Issue Feature Papers in Physical Chemistry and Chemical Physics 2022)

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19 pages, 5359 KiB

Open AccessArticle

Cellulose-Based Hectocycle Nanopolymers: Synthesis, Molecular Docking and Adsorption of Difenoconazole from Aqueous Medium

by Bayan Khalaf, Othman Hamed, Shehdeh Jodeh, Roland Bol, Ghadir Hanbali, Zaki Safi, Omar Dagdag, Avni Berisha and Subhi Samhan

Int. J. Mol. Sci. 2021, 22(11), 6090; https://doi.org/10.3390/ijms22116090 - 4 Jun 2021

Cited by 29 | Viewed by 3501

Abstract

The goal of this work was to develop polymer-based heterocycle for water purification from toxic pesticides such as difenoconazole. The polymer chosen for this purpose was cellulose nanocrystalline (CNC); two cellulose based heterocycles were prepared by crosslinking with 2,6-pyridine dicarbonyl dichloride (Cell-X), and [...] Read more.

The goal of this work was to develop polymer-based heterocycle for water purification from toxic pesticides such as difenoconazole. The polymer chosen for this purpose was cellulose nanocrystalline (CNC); two cellulose based heterocycles were prepared by crosslinking with 2,6-pyridine dicarbonyl dichloride (Cell-X), and derivatizing with 2-furan carbonyl chloride (Cell-D). The synthesized cellulose-based heterocycles were characterized by SEM, proton NMR, TGA and FT-IR spectroscopy. To optimize adsorption conditions, the effect of various variable such as time, adsorbent dose, pH, temperature, and difenoconazole initial concentration were evaluated. Results showed that, the maximum difenoconazole removal percentage was about 94.7%, and 96.6% for Cell-X and Cell-D, respectively. Kinetic and thermodynamic studies on the adsorption process showed that the adsorption of difenoconazole by the two polymers is a pseudo-second order and follows the Langmuir isotherm model. The obtained values of ∆G ° and ∆H suggest that the adsorption process is spontaneous at room temperature. The results showed that Cell-X could be a promising adsorbent on a commercial scale for difenoconazole. The several adsorption sites present in Cell-X in addition to the semi crown ether structure explains the high efficiency it has for difenoconazole, and could be used for other toxic pesticides. Monte Carlo (MC) and Molecular Dynamic (MD) simulation were performed on a model of Cell-X and difenoconazole, and the results showed strong interaction. Full article

(This article belongs to the Special Issue Feature Papers in Physical Chemistry and Chemical Physics 2022)

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Review

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27 pages, 1265 KiB

Open AccessReview

Application of Vibrational Spectroscopic Techniques in the Study of the Natural Polysaccharides and Their Cross-Linking Process

by Barbara Gieroba, Grzegorz Kalisz, Mikolaj Krysa, Maryna Khalavka and Agata Przekora

Int. J. Mol. Sci. 2023, 24(3), 2630; https://doi.org/10.3390/ijms24032630 - 30 Jan 2023

Cited by 28 | Viewed by 4595

Abstract

Polysaccharides are one of the most abundant natural polymers and their molecular structure influences many crucial characteristics—inter alia hydrophobicity, mechanical, and physicochemical properties. Vibrational spectroscopic techniques, such as infrared (IR) and Raman spectroscopies are excellent tools to study their arrangement during polymerization and [...] Read more.

Polysaccharides are one of the most abundant natural polymers and their molecular structure influences many crucial characteristics—inter alia hydrophobicity, mechanical, and physicochemical properties. Vibrational spectroscopic techniques, such as infrared (IR) and Raman spectroscopies are excellent tools to study their arrangement during polymerization and cross-linking processes. This review paper summarizes the application of the above-mentioned analytical methods to track the structure of natural polysaccharides, such as cellulose, hemicellulose, glucan, starch, chitosan, dextran, and their derivatives, which affects their industrial and medical use. Full article

(This article belongs to the Special Issue Feature Papers in Physical Chemistry and Chemical Physics 2022)

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43 pages, 12593 KiB

Open AccessReview

Survey on Adsorption of Low Molecular Weight Compounds in Cu-BTC Metal–Organic Framework: Experimental Results and Thermodynamic Modeling

by Antonio Baldanza, Domenico Mallamace, Giuseppe Mensitieri, Cosimo Brondi, Pellegrino Musto and Giuseppe Scherillo

Int. J. Mol. Sci. 2022, 23(16), 9406; https://doi.org/10.3390/ijms23169406 - 20 Aug 2022

Cited by 3 | Viewed by 1977

Abstract

This contribution aims at providing a critical overview of experimental results for the sorption of low molecular weight compounds in the Cu-BTC Metal–Organic Framework (MOF) and of their interpretation using available and new, specifically developed, theoretical approaches. First, a literature review of experimental [...] Read more.

This contribution aims at providing a critical overview of experimental results for the sorption of low molecular weight compounds in the Cu-BTC Metal–Organic Framework (MOF) and of their interpretation using available and new, specifically developed, theoretical approaches. First, a literature review of experimental results for the sorption of gases and vapors is presented, with particular focus on the results obtained from vibrational spectroscopy techniques. Then, an overview of theoretical models available in the literature is presented starting from semiempirical theoretical approaches suitable to interpret the adsorption thermodynamics of gases and vapors in Cu-BTC. A more detailed description is provided of a recently proposed Lattice Fluid approach, the Rigid Adsorbent Lattice Fluid (RALF) model. In addition, to deal with the cases where specific self- and cross-interactions (e.g., H-bonding, Lewis acid/Lewis base interactions) play a role, a modification of the RALF model, i.e., the RALFHB model, is introduced here for the first time. An extension of both RALF and RALFHB is also presented to cope with the cases in which the heterogeneity of the rigid adsorbent displaying a different kind of adsorbent cages is of relevance, as it occurs for the adsorption of some low molecular weight substances in Cu-BTC MOF. Full article

(This article belongs to the Special Issue Feature Papers in Physical Chemistry and Chemical Physics 2022)

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29 pages, 1929 KiB

Open AccessReview

Nanosecond Pulsed Electric Field (nsPEF): Opening the Biotechnological Pandora’s Box

by Alvaro R. Ruiz-Fernández, Leonardo Campos, Sebastian E. Gutierrez-Maldonado, Gonzalo Núñez, Felipe Villanelo and Tomas Perez-Acle

Int. J. Mol. Sci. 2022, 23(11), 6158; https://doi.org/10.3390/ijms23116158 - 31 May 2022

Cited by 21 | Viewed by 4999

Abstract

Nanosecond Pulsed Electric Field (nsPEF) is an electrostimulation technique first developed in 1995; nsPEF requires the delivery of a series of pulses of high electric fields in the order of nanoseconds into biological tissues or cells. They primary effects in cells is the [...] Read more.

Nanosecond Pulsed Electric Field (nsPEF) is an electrostimulation technique first developed in 1995; nsPEF requires the delivery of a series of pulses of high electric fields in the order of nanoseconds into biological tissues or cells. They primary effects in cells is the formation of membrane nanopores and the activation of ionic channels, leading to an incremental increase in cytoplasmic Ca

^{2 +}

concentration, which triggers a signaling cascade producing a variety of effects: from apoptosis up to cell differentiation and proliferation. Further, nsPEF may affect organelles, making nsPEF a unique tool to manipulate and study cells. This technique is exploited in a broad spectrum of applications, such as: sterilization in the food industry, seed germination, anti-parasitic effects, wound healing, increased immune response, activation of neurons and myocites, cell proliferation, cellular phenotype manipulation, modulation of gene expression, and as a novel cancer treatment. This review thoroughly explores both nsPEF’s history and applications, with emphasis on the cellular effects from a biophysics perspective, highlighting the role of ionic channels as a mechanistic driver of the increase in cytoplasmic Ca

^{2 +}

concentration. Full article

(This article belongs to the Special Issue Feature Papers in Physical Chemistry and Chemical Physics 2022)

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51 pages, 2741 KiB

Open AccessReview

The Interplay between the Theories of Mode Coupling and of Percolation Transition in Attractive Colloidal Systems

by Francesco Mallamace, Giuseppe Mensitieri, Martina Salzano de Luna, Paola Lanzafame, Georgia Papanikolaou and Domenico Mallamace

Int. J. Mol. Sci. 2022, 23(10), 5316; https://doi.org/10.3390/ijms23105316 - 10 May 2022

Cited by 1 | Viewed by 1959

Abstract

In the recent years a considerable effort has been devoted to foster the understanding of the basic mechanisms underlying the dynamical arrest that is involved in glass forming in supercooled liquids and in the sol-gel transition. The elucidation of the nature of such [...] Read more.

In the recent years a considerable effort has been devoted to foster the understanding of the basic mechanisms underlying the dynamical arrest that is involved in glass forming in supercooled liquids and in the sol-gel transition. The elucidation of the nature of such processes represents one of the most challenging unsolved problems in the field of material science. In this context, two important theories have contributed significantly to the interpretation of these phenomena: the Mode-Coupling theory (MCT) and the Percolation theory (PT). These theories are rooted on the two pillars of statistical physics, universality and scale laws, and their original formulations have been subsequently modified to account for the fundamental concepts of Energy Landscape (EL) and of the universality of the fragile to strong dynamical crossover (FSC). In this review, we discuss experimental and theoretical results, including Molecular Dynamics (MD) simulations, reported in the literature for colloidal and polymer systems displaying both glass and sol-gel transitions. Special focus is dedicated to the analysis of the interferences between these transitions and on the possible interplay between MCT and PT. By reviewing recent theoretical developments, we show that such interplay between sol-gel and glass transitions may be interpreted in terms of the extended F13 MCT model that describes these processes based on the presence of a glass-glass transition line terminating in an A3 cusp-like singularity (near which the logarithmic decay of the density correlator is observed). This transition line originates from the presence of two different amorphous structures, one generated by the inter-particle attraction and the other by the pure repulsion characteristic of hard spheres. We show here, combining literature results with some new results, that such a situation can be generated, and therefore experimentally studied, by considering colloidal-like particles interacting via a hard core plus an attractive square well potential. In the final part of this review, scaling laws associated both to MCT and PT are applied to describe, by means of these two theories, the specific viscoelastic properties of some systems. Full article

(This article belongs to the Special Issue Feature Papers in Physical Chemistry and Chemical Physics 2022)

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20 pages, 8535 KiB

Open AccessReview

HOFs Built from Hexatopic Carboxylic Acids: Structure, Porosity, Stability, and Photophysics

by Maria Rosaria di Nunzio, Yuto Suzuki, Ichiro Hisaki and Abderrazzak Douhal

Int. J. Mol. Sci. 2022, 23(4), 1929; https://doi.org/10.3390/ijms23041929 - 9 Feb 2022

Cited by 15 | Viewed by 3513

Abstract

Hydrogen-bonded organic frameworks (HOFs) have attracted renewed attention as another type of promising candidates for functional porous materials. In most cases of HOF preparation, the applied molecular design principle is based on molecules with rigid π-conjugated skeleton together with more than three H-bonding [...] Read more.

Hydrogen-bonded organic frameworks (HOFs) have attracted renewed attention as another type of promising candidates for functional porous materials. In most cases of HOF preparation, the applied molecular design principle is based on molecules with rigid π-conjugated skeleton together with more than three H-bonding groups to achieve 2D- or 3D-networked structures. However, the design principle does not always work, but results in formation of unexpected structures, where subtle structural factors of which we are not aware dictate the entire structure of HOFs. In this contribution, we assess recent advances in HOFs, focusing on those composed of hexatopic building block molecules, which can provide robust frameworks with a wide range of topologies and properties. The HOFs described in this work are classified into three types, depending on their H-bonded structural motifs. Here in, we focus on: (1) the chemical aspects that govern their unique fundamental chemistry and structures; and (2) their photophysics at the ensemble and single-crystal levels. The work addresses and discusses how these aspects affect and orient their photonic applicability. We trust that this contribution will provide a deep awareness and will help scientists to build up a systematic series of porous materials with the aim to control both their structural and photodynamical assets. Full article

(This article belongs to the Special Issue Feature Papers in Physical Chemistry and Chemical Physics 2022)

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20 pages, 1074 KiB

Open AccessReview

Dynamic “Molecular Portraits” of Biomembranes Drawn by Their Lateral Nanoscale Inhomogeneities

by Roman G. Efremov

Int. J. Mol. Sci. 2021, 22(12), 6250; https://doi.org/10.3390/ijms22126250 - 10 Jun 2021

Cited by 11 | Viewed by 2562

Abstract

To date, it has been reliably shown that the lipid bilayer/water interface can be thoroughly characterized by a sophisticated so-called “dynamic molecular portrait”. The latter reflects a combination of time-dependent surface distributions of various physicochemical properties, inherent in both model lipid bilayers and [...] Read more.

To date, it has been reliably shown that the lipid bilayer/water interface can be thoroughly characterized by a sophisticated so-called “dynamic molecular portrait”. The latter reflects a combination of time-dependent surface distributions of various physicochemical properties, inherent in both model lipid bilayers and natural multi-component cell membranes. One of the most important features of biomembranes is their mosaicity, which is expressed in the constant presence of lateral inhomogeneities, the sizes and lifetimes of which vary in a wide range—from 1 to 10³ nm and from 0.1 ns to milliseconds. In addition to the relatively well-studied macroscopic domains (so-called “rafts”), the analysis of micro- and nanoclusters (or domains) that form an instantaneous picture of the distribution of structural, dynamic, hydrophobic, electrical, etc., properties at the membrane-water interface is attracting increasing interest. This is because such nanodomains (NDs) have been proven to be crucial for the proper membrane functioning in cells. Therefore, an understanding with atomistic details the phenomena associated with NDs is required. The present mini-review describes the recent results of experimental and in silico studies of spontaneously formed NDs in lipid membranes. The main attention is paid to the methods of ND detection, characterization of their spatiotemporal parameters, the elucidation of the molecular mechanisms of their formation. Biological role of NDs in cell membranes is briefly discussed. Understanding such effects creates the basis for rational design of new prospective drugs, therapeutic approaches, and artificial membrane materials with specified properties. Full article

(This article belongs to the Special Issue Feature Papers in Physical Chemistry and Chemical Physics 2022)

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