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The major factor that drives a protein toward collapse and folding is the hydrophobic effect. At the folding process a hydrophobic core is shielded by the solvent-accessible surface area of the protein. We study the behavior of the numbers in 5526 protein structures present in the Brookhaven Protein Data Bank. The first digit of mass, volume, average radius and solvent-accessible surface area are measured independently and we observe that most of these geometric observables obey the Newcomb–Benford law. That is volume, mass and average radius obey the Newcomb–Benford law. Nevertheless, the digits of the solvent-accessible surface area do not agree with the Newcomb–Benford law. The present findings indicate that the hydrophobic effect is responsible for the anomalous first digit behavior of solvent-accessible surface areas.

The potential of mean forces (PMFs) has been determined for an isobutane dimer in various solvent environments such as water, methanol and acetonitrile at a temperature of 298 K and pressure of 1 bar using GROMACS software. All the molecular dynamics (MD) simulations are carried out using a TIP3P water model under a CHARMM36 forcefield. Following Umbrella Sampling technique, PMFs are calculated and analyzed using Weighted Histogram Analysis Method (WHAM) and coordination number of first solvation shell is extracted for all solvents using radial distribution function. The shape of PMFs contains contact minima, solvent-separated minima and desolvation maxima. The values of contact minima are not affected much by solvent environment and found to be at 0.5377, 0.5480 and 0.5495 nm for water, methanol and acetonitrile respectively. The corresponding energy depths are found −0.9134, −0.7080 and −0.5295 kcalmol${}^{-1}$. The variation observed at solvent-separated minima is noticeable and found at 0.9012, 0.9721 and 0.9151 nm for water, methanol and acetonitrile, respectively. The coordination number of the first solvation shell by taking an isobutane molecule as a reference from their center of mass is found to be 28.1, 16.9 and 14.8 for water, methanol and acetonitrile, respectively. There is a soft hydrophobic interaction between isobutane dimer and solvents like methanol and acetonitrile relative to water, might be due to the presence of competitive methyl group of methanol and acetonitrile in the solvent medium.

Anisotropic surfaces with micropillar- or micropillar/nanobump structures and anisotropic wetting behavior were fabricated. Structures were arranged as three parallel zones where the structure of the middle zone differed from that of the edge zones. The widths of the middle zones were increased systematically, and the effects of the middle zone structures and widths on the contact and sliding angles of water were investigated. Structures were fabricated on PP by injection molding. Microstructured mold inserts for injection molding were obtained by structuring aluminum foils with a microworking robot, and hierarchically structured mold inserts by anodizing the microstructured foils. It was possible to create surfaces where the microstructure in the middle zone was lower or higher than on the edges, or where the middle zone had only nanostructure or was unstructured. The behavior of water on the surfaces was characterized by measuring the dynamic contact angles and sliding angles parallel and perpendicular to the zones. Hydrophobic surfaces were achieved. With appropriate middle zone widths, clearly differing parallel and perpendicular contact angles were measured and elongation of droplets along the middle zones was detected.

Plasma pretreatment is an eco-friendly process employed to modify the surface properties and improve the adhesion properties of tasar silk fabrics. The plasma pretreatment has been carried out in DC glow discharge plasma at constant power and for different treatment durations (5, 10 and 30min). ZnO nanoparticles (ZnO NPs) play a significant role in antibacterial, cleaning and UV protection. ZnO NPs have been synthesized by the wet chemical method and the average crystallite size of the same is found to be 49nm using X-ray diffraction (XRD). Plasma treated silk fabrics are coated with ZnO NPs using vacuum thermal evaporation technique. Structural and chemical change of raw, untreated and plasma treated silk fabrics coated with ZnO NPs are analyzed by XRD and attenuated total reflection Fourier transform infrared (ATR-FTIR) studies. The surface morphologies of all the fabrics are analyzed by using scanning electron microscope (SEM), which confirms the adherence of ZnO NPs on the surface of the fabrics. Elemental analysis is carried out using energy dispersive spectroscopy, which confirms the presence of ZnO NPs on the surface of the fabrics. The improved surface property in terms of hydrophobicity is analyzed by using a contact angle test. It is found that the plasma pretreated silk fabrics coated with ZnO NPs have better antibacterial activities against Escherichia Coli bacteria.

To study the hydrophobic properties of Betula alnoides wood modified by alkyltrichlorosilanes, four alkyltrichlorosilanes with different chain lengths were used to prepare hydrolytic solutions by adding 0.25% (v/v) of alkyltrichlorosilane to anhydrous toluene, and the wood samples were immersed in the hydrolytic solutions for 4 h. The surface chemical compositions of the samples were analyzed by X-ray photoelectron spectroscopy (XPS) and Varian 640-IR Fourier Infrared Spectrometer (ATR-FTIR), the surface morphology of the samples was observed by scanning electron microscopy (SEM), and the wettability of the modified wood was investigated using an optical contact angle goniometer. The results demonstrated that treatment with alkyltrichlorosilanes introduced Si and low surface energies of –CH₂ and –CH₃ on the surface of Betula alnoides wood. The –CH₂ and –CH₃ content increased with the increase in chain length. Alkyltrichlorosilanes formed a different micro or nanoscale roughness on the surfaces of the wood samples. The water contact angles of all coatings of alkyltrichlorosilanes are greater than $131.3\pm 2.4^{\circ }$, and greater than $115.5\pm 0.9^{\circ }$ after 180 s. The water absorption decreases with the increase in chain length. The water absorption of the uncoated sample is $44.0\pm 1.9$ wt.%, while those of samples modified by MTCS and OTCS are $18.0\pm 0.9$ wt.% and $11.0\pm 0.0$ wt.%, respectively.

The study shows that the materials of interfacial formations formed at the interface of two immiscible liquids, an aqueous solution of a lanthanide salt and a solution of di(2-ethylhexyl)phosphoric acid in a solvent, can have different hydrophobicity depending on the synthesis time. The surface roughness and the contact angle of the substance transferred to different substrates (glass, duralumin, copper) were measured. It was established that external vibration in the interfacial layer of the system during synthesis and self-assembly affects the hydrophobicity of the substance. A dependence between the contact angle and the surface roughness was established.

Metallic Al was doped into amorphous carbon (a-C) to form a matrix of a-C(Al) of very low residual stress and high toughness at the expense of some hardness. Nanocrystallites of TiC (nc-TiC) of a few nanometers in size were embedded in this matrix to bring back the hardness. The nanocomposite coating of nc-TiC/a-C(Al) was deposited via co-sputtering of graphite, Ti, and Al targets. Although the nanocomposite coating exhibited a moderately high hardness (about 20 GPa), it possessed extremely high toughness (about 55% of plasticity during indentation deformation) and low residual stress (less than 0.4 GPa), smooth (R_a=5.5 nm), and hydrophobic surface (contact angle with water reaches 100°).

In this paper, a simple, low-cost and efficient method was adopted to fabricate large-area Si nanowire (SiNW) arrays by inserting the p-type (100) silicon wafer into aqueous HF + AgNO₃ solution for a certain time at room temperature. Surface of the silicon wafer with high aspect ratio SiNW shows the characteristics of low-reflection as low as 5% in the 450–800 nm wavelength range, especially less than 1% after etching for 60 min. The surface also exhibits super-hydrophobicity with water contact angle up to 150°. We investigated the relationship between the etching duration and aspect ratio of the SiNW systematically and demonstrated that the aspect ratio of the SiNW can be controlled. The antireflection surface shows a potential implication in increasing the conversation efficiency for solar cells, and the self-cleaning properties will further enhance the resistance to environment conditions for a long-life work.

The uniformity, elasticity and hydrophobicity of methyltrimethoxysilane (MTMS)-based silica aerogels, which were prepared by using dimethyl sulfoxide (DMSO) as the solvent, were investigated. The as-prepared silica aerogels were characterized by means of scanning electron microscope, Fourier transform infrared, contact angle/interface system and electronic universal testing machine. The hydrophobicity of the MTMS-based silica aerogels could be adjusted by tuning the MTMS/DMSO molar ratios. The water contact angle of the MTMS-based silica aerogels could be as high as 160.2^∘, suggesting its superhydrophobic property. It was found that all the MTMS-based silica aerogels had the typical three-dimensional porous structure. The failure strain of MTMS-based silica aerogels could be as high as 66.14%.

Solute transporters (STs) are an important subgroup of integral membrane proteins that facilitate the translocation of a diverse range of solutes such as sugars, amino acids, and neurotransmitters across cell membranes. Sequence analysis indicates that STs possess multiple stretches of hydrophobic-rich amino acids that are organized into the transmembrane domains (TMDs) of the functional protein, but exactly how the correct spatial arrangement of these domains is achieved remains a challenging problem. We hypothesized that perhaps differences in interdomain hydrophobicity might play some role in this process. To test this hypothesis, we generated a heptadic model of the alpha helix and mapped the average hydrophobicities (coaxial) and hydrophobic moments (radial) of 108 TMDs found in 9 different human ST proteins. Our results, taken together with earlier work from other groups, suggest that spatial patterns of hydrophobicity found in TMDs 1 and 2 are consistent with a role for these domains in the initial anchoring of the nascent ST protein to the endoplasmic reticulum (ER), as it emerges from the ribosome complex and perhaps in the subsequent spatial organisation of STs.

Plasma-induced surface graft copolymerization of acrylic acid on polypropylene non-woven fabric (PP-g-AA) and polypropylene membrane were reported. The extents of grafting were controlled by the plasma and polymerization condition. Hexadecyltrimethyl ammonium bromide was then coupled with the carboxyl group of PP-g-AA to obtain a polyion complex (PIC). At last, CF₄ plasma was used to give PICs hydrophobic property. The moisture regain and water-repellency of the processed PICs was investigated. The surfaces were characterized using ATR FT-IR and XPS. The result indicates that the products have very high ability to adsorb moisture, even better than cotton fiber. At the same time, the products show excellent hydrophobic property, which can't be wetted by those reagents whose surface tensions were higher than 327 mN/m.

Remarkable progress has been achieved in organometallic halide perovskite solar cells (PSCs). However, poor environmental stability of PSCs has been proved to be challenging and needs further improvement. Here, a strategy of butylated hydroxytoluene (BHT) antioxidant additive with hydrophobic tert butyl and hydrophilic hydroxyl is developed to enhance the hydrophobicity, control nucleation rate and passivate the defect states of perovskite. The tert butyl group effectively prevents the penetration of moisture, as well as the formed hydrogen bond between hydroxyl group and iodine controls the assembly process of BHT and perovskite. By optimizing weight ratio of BHT and MAPbI₃ in precursor solution, the power conversion efficiency of PSCs increased from 14.93% to 18.28% and greatly enhanced device stability compared with control device. We believe that our tactic of BHT additive can be applied to various perovskite films and will facilitate the realization of stable perovskite optoelectronics.

Surface coatings such as hydrophobic and transparent coatings were applied to cement concrete surfaces using Polydimethylsiloxane (PDMS) coatings, which have nanometer-sized particles. The degree of contact between the liquid and the coated surface reveals the surface’s ability to repel water, commonly referred to as hydrophobicity. By depositing silicon coating on the surface, we successfully achieved superhydrophobicity on cement concrete, providing excellent resistance against water damage. We are striving to replicate the natural superhydrophobic properties found in nature to create artificial surfaces with similar characteristics. In this study, we experimented to develop and evaluate superhydrophobic coatings on cement concrete. The application of PDMS on the cement concrete yielded fascinating results, with the typical contact angle of the coated layer measuring 178 degrees. We utilized ImageJ software to analyze the results. This innovative approach holds great promise for enhancing water repellency in the field of construction.

The ligands exchange process on the gold nanoparticles (GNPs) was studied in toluene solution. The self-assembled film was prepared by mixing the toluene and aqueous solution which contained hydrophobic group (PPh₃) and hydrophilic group (THPO), respectively. The results showed that a layer of film was formed at the liquid-liquid interface of toluene and aqueous solution. The ligands exchange resulted in the reduction of bare surface of GNPs and the differential capacity according to the electrochemical measurement. The ratio of hydrophobic group and hydrophilic group was about 0.93:1 which was measured by FTIR and XPS analysis demonstrating the formation of Janus gold nanoparticles. The ligand exchange mechanism could be described as that the THPO molecule on the gold nanoparticles was replaced by the PPh₃ molecules.

Streptococcus agalactiae (GBS) is a human pathogen, that forms biofilms in vitro with variable efficiency. Aim of this study was to investigate the relationships between hydrophobicity and the ability of GBS to form biofilm. Twenty strains of GBS were investigated for the purpose. Biofilm experiments were performed, in unmodified atmosphere, in 96-well polystyrene microtiter plates containing Todd-Hewitt Broth. Increasing concentrations of glucose were also investigated for their influence on both hydrophobicity and biofilm production. The quantitative measurement was achieved by means of colorimetric methods using crystal violet. The hydrophobicity was investigated by using the hexadecane test, and expressed as percent of hydrophobicity. The hydrophobicity varied a little in most cases and independently of glucose concentrations, while BI increased with increasing concentration of glucose. Although most of the strains had a hydrophobicity index of > 80%, any correlation between hydrophobicity and biofilm formation has not been found.