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Cupriavidus necator can produce single-cell proteins (SCPs) using electrons produced by hydrogen as energy, oxygen as electron acceptors, and CO2 as carbon sources. Gas fermentation is a process of microbial fermentation that uses gas substrates (such as hydrogen, carbon dioxide, etc.) which faces several challenges, mainly including the low solubility of gas substrates, the danger of hydrogen and oxygen mixing, and the optimization of fermentation conditions. To overcome these challenges, this article explores a variety of strategies—including the design of a self-developed bioreactor—to reduce the risk of static electricity. Without the addition of filler material, the results showed that the maximum cell dry weight (CDW) of 30% secondary seed inoculation was 20.41% higher than that of 10% secondary seed inoculum, and 5.99% higher than that of 20% secondary seed inoculum. Combined with the filler material and with the use of high-efficiency continuous fermentation technology, the average yield of continuous fermentation was 23.31 g/day, while the average yield of batch fermentation was 14.33 g/day. The daily yield of continuous fermentation is 1.63 times that of batch fermentation. These efforts are aimed at improving the efficiency and safety of gas fermentation. [ABSTRACT FROM AUTHOR]

Polyester fibers tend to generate static electricity during the weaving and application processes, posing a threat to their production. Enhancing the water absorbency and electrical conductivity of polyester fibers themselves is an effective approach to improving their antistatic properties. In this study, multifunctional chitosan (CS), sodium phytate (SP), and Cu2+ were loaded on polyester fibers through layer-by-layer (LBL) self-assembly. The antistatic and water absorption capability of the modified polyester fibers was investigated by designing different process parameters combined with a surface resistance test and water contact angle tests. The antistatic property test results confirmed the positive effect of CS and Cu2+ on discharging electrostatic charge. Within a definite scope, with the increase in the number of assembly layers, assembly duration, and the concentration of the assembly substances, the wettability of the modified polyester fibers became more favorable and the antistatic effect became more remarkable. [ABSTRACT FROM AUTHOR]

Improving the filtration efficiency of air filter materials is an ongoing research goal. This study conducted in-depth research on a new reduced graphene oxide air filter material, and the differences in its performance and conductivity durability before and after eliminating static electricity were tested and analyzed. The results showed that the filtration efficiency of the reduced graphene oxide air filter material significantly decreased after eliminating static electricity. The maximum decrease in filtration efficiency was observed at a filtration velocity of 0.8 m/s, with PM10 > PM1.0 > PM2.5. In this case, the filtration efficiency decreased by 11.8%, 7.98%, and 7.17%, respectively. The maximum difference in filtration efficiency of 0.29 μm particulates was about 12.7%. Eliminating static electricity slightly increased the resistance (2.5~15.5 Pa). In addition, the new reduced graphene oxide air filter material exhibited good conductivity and stability after continuous testing. This study provides data support for the application of subsequent electrification sterilization, reference values for multi-angle applications, and the development of new composite air filter materials. [ABSTRACT FROM AUTHOR]

Contact electrification (CE), a common physical phenomenon, is worth discussing. However, there are few reports on the influence of atmosphere on CE, or on the performance of triboelectric nanogenerators (TENG), based on CE by encapsulating gas inside. Here, we propose physical processes of electron transfer to interpret the impact of the gaseous atmosphere on CE. An atmosphere-filled triboelectric nanogenerator (AF-TENG) encapsulated five different gas-components of air based on the vertical contact separation mode was prepared. The sensitivity (1.02 V·N−1) and the power density (9.63 μW·m−2) of the oxygen-atmosphere-filled AF-TENG were 229.03% and 157.81% higher than these (0.31 V·N−1 and 3.84 μW·m−2) of the nitrogen-atmosphere-filled AF-TENG. As the oxygen atom possesses more atomic energy levels than other atoms, this could act as a "bridge" for more electrons to directly transfer between the two materials. The device package under different atmospheres could not only strengthen understanding of CE and improve the performance of TENG, but also be potentially applicable to prevent and control unnecessary damage caused by static electricity. [ABSTRACT FROM AUTHOR]

This work studies the use of Fe/Ni-MOFs for the removal of ciprofloxacin (CIP) in wastewater. Fe/Ni-MOFs are prepared by the solvothermal method and characterized by X-ray diffraction (XRD), a scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), and a thermal gravimetric analyzer (TG). Under the conditions of the concentration of 50 ppm, a mass of 30 mg, and a temperature of 30 °C, the maximum adsorption capacity of ciprofloxacin removal within 5 h was 232.1 mg/g. The maximum removal rate was 94.8% when 40 mg of the Fe/Ni-MOFs was added to the solution of 10 ppm ciprofloxacin. According to the pseudo-second-order (PSO) kinetic model, the R2 values were all greater than 0.99, which proved that the adsorption theory of ciprofloxacin by Fe/Ni-MOFs was consistent with the practice. The adsorption results were mainly affected by solution pH and static electricity, as well as other factors. The Freundlich isotherm model characterized the adsorption of ciprofloxacin by Fe/Ni-MOFs as multilayer adsorption. The above results indicated that Fe/Ni-MOFs were effective in the practical application of ciprofloxacin removal. [ABSTRACT FROM AUTHOR]

In order to study the effect of inorganic salt additives on the surface tension of a sodium dodecylbenzene sulfonate (SDBS) solution, the surface tension of the mixed system of six common inorganic salt additives, NaCl, CaCl2, AlCl3, Na2SO4, Na2CO3, and NaHCO3, and SDBS was measured, and the effects of the inorganic salt types, surfactant concentrations and inorganic salt concentrations on the surface tension of the SDBS solution were studied. On this basis, three inorganic salts, NaCl, CaCl2 and Na2SO4, were selected, and their effects on the critical micelle concentration (CMC) of the SDBS solution were studied. The experimental results showed that different inorganic salts had different effects on the surface tension of the SDBS solution. The order of effect of the six inorganic salts on the surface tension of the SDBS solution was CaCl2 > NaCl > Na2SO4 > NaHCO3 > Na2CO3 > AlCl3; when the mass fraction of the SDBS solution is high, the influence of the inorganic salts on the surface tension of the SDBS solution is relatively small; with an increase in the concentration of the preferred inorganic salt additives, the surface tension of the SDBS solution decreases first, then tends to be stable, and then increases; a reduction in the critical micelle concentration by the three selected inorganic salt additives shows the trend of 0.7% NaCl > 0.5% CaCl2 > 0.5% Na2SO4. [ABSTRACT FROM AUTHOR]

Microplastic pollution is widespread around the world and inevitably comes into contact with organisms. With the accumulation of microplastics in the environment, the negative impact of microplastics on organisms has become the main focus in the field of microplastics. In this study, the different particle and concentration effects of fluorescent polystyrene microplastics (PS-MPs) on Nostocaceae and Daphnia Magna were researched. The results indicate that PS-MPs adhered to Nostocaceae through static electricity, which hindered the absorption of photons and CO2 by Nostocaceae, resulting in a decrease in chlorophyll, a low growth rate and high mortality for Nostocaceae. PS-MPs with very small particles may be integrated into the blood of Daphnia Magna, leading to an increasing trend of mortality and a decrease in spawning rate. The research provides basic data and a reference for the effect of PS-MPs on freshwater organisms and has implications for the further study of microplastics. [ABSTRACT FROM AUTHOR]

Touchless technology has garnered significant interest in recent years because of its effectiveness in combating infectious diseases such as the novel coronavirus (COVID-19). The goal of this study was to develop an inexpensive and high-precision touchless technology. A base substrate was coated with a luminescent material that emitted static-electricity-induced luminescence (SEL), and it was applied at high voltage. An inexpensive web camera was used to verify the relationship between the non-contact distance to a needle and the applied-voltage-triggered luminescence. The SEL was emitted at 20–200 mm from the luminescent device upon voltage application, and the web camera detected the SEL position with an accuracy of less than 1 mm. We used this developed touchless technology to demonstrate a highly accurate real-time detection of the position of a human finger based on SEL. [ABSTRACT FROM AUTHOR]

The human transmembrane protease, serine 2 (TMPRSS2), essential for SARS-CoV-2 entry, is a key antiviral target. Here, we computationally profiled the TMPRSS2-binding affinities of 15 antiviral compounds. Molecular dynamics (MD) simulations for the docked complexes revealed that three compounds exited the substrate-binding cavity (SBC), suggesting noncompetitive inhibition. Of the remaining compounds, five charged ones exhibited reduced binding stability due to competing electrostatic interactions and increased solvent exposure, while seven neutral compounds showed stronger binding affinity driven by van der Waals (vdW) interactions compensating for unfavorable electrostatic effects (including electrostatic interactions and desolvation penalties). Positive and negative hotspot residues were identified as uncharged and charged, respectively, both lining the SBC. Despite forming diverse interactions with compounds, the burial of positive hotspots led to strong vdW interactions that overcompensated for unfavorable electrostatic effects, whereas negative hotspots incurred high desolvation penalties, negating any favorable contributions. Charged residues at the SBC's outer rim can reduce binding affinity significantly when forming hydrogen bonds or salt bridges. These findings underscore the importance of enhancing vdW interactions with uncharged residues and minimizing the unfavorable electrostatic effects of charged residues, providing valuable insights for designing effective TMPRSS2 inhibitors.

(1) Background: Electrostatics plays a capital role in protein-protein and protein-ligand interactions. Implicit solvent models are widely used to describe electrostatics and complementarity at interfaces. Electrostatic complementarity at the interface is not trivial, involving surface potentials rather than the charges of surfacial contacting atoms. (2) Results: The program bluues_cplx, here used in conjunction with the software NanoShaper to compute molecular surfaces, has been used to compute the electrostatic properties of 756 protein-protein and 189 protein-ligand complexes along with the corresponding isolated molecules. (3) Methods: The software we make available here uses Generalized Born (GB) radii, computed by a molecular surface integral, to output several descriptors of electrostatics at protein (and in general, molecular) interfaces. We illustrate the usage of the software by analyzing a dataset of protein-protein and protein-ligand complexes, thus extending and refining previous analyses of electrostatic complementarity at protein interfaces. (4) Conclusions: The complete analysis of a molecular complex is performed in tens of seconds on a PC, and the results include the list of surfacial contacting atoms, their charges and Pearson correlation coefficient, the list of contacting surface points with the electrostatic potential (computed for the isolated molecules) and Pearson correlation coefficient, the electrostatic and hydrophobic free energy with different contributions for the isolated molecules, their complex and the difference for all terms. The software is readily usable for any molecular complex in solution.

Electrostatic spray drying (ESD) of a milk protein matrix comprising whey protein isolate (WPI), skim milk powder (SMP), and lactose was compared to conventional spray drying (CSD) and freeze-drying (FD). ESD and CSD were used to produce powders at low (0.12-0.14), medium (0.16-0.17), and high (0.31-0.36) levels of water activity (a w ), while FD powders targeted low a w (0.12). Maillard reaction indicators were studied after drying and during storage for up to 28 days at 20, 40, or 60 °C by measuring free -NH 2 groups, as an indicator of available lysine, and 5-hydroxymethylfurfural (HMF). After drying, levels of residual free -NH 2 groups were ~15% higher in ESD and FD powders than in their CSD counterparts. CSD powders also had ~14% higher HMF concentrations compared to their ESD and FD counterparts. Storage led to reductions in free -NH 2 groups and increases in HMF content in all powders, the extent of which increased with increasing storage temperature. Reductions in free -NH 2 groups followed first-order reaction kinetics at 20 and 40 °C but second-order reaction kinetics at 60 °C. Lactose crystallization was detected in high-a w CSD powders after 14 d at 40 °C and in both CSD and ESD powders after 7 d at 60 °C. Overall, we found that ESD is a gentle drying technology which enables production of powders with lower Maillard reaction markers.

Living systems cannot rely on random intermolecular approaches toward cell crowding, and hidden mechanisms must be present to favor only those molecular interactions required explicitly by the biological function. Electromagnetic messaging among proteins is proposed from the observation that charged amino acids located on the protein surface are mostly in adjacent sequence positions and/or in spatial proximity. Molecular dynamics (MD) simulations have been used to predict electric charge proximities arising from concerted motions of charged amino acid side chains in two protein model systems, human ubiquitin and the chitinolytic enzyme from Ostrinia furnacalis . This choice has been made for their large difference in size and sociality. Protein electrodynamics seems to emerge as the framework for a deeper understanding of the long-distance interactions of proteins with their molecular environment. Our findings will be valuable in orienting the design of proteins with specific recognition patterns.

Affected by global warming, permafrost degradation releases a large amount of methane gas, and this part of flammable methane may increase the frequency of wildfires. To study the influence mechanism of methane emission on wildfires in degraded permafrost regions, we selected the northwest section of Xiaoxing'an Mountains in China as the study area, and combined with remote sensing data, we conducted long-term monitoring of atmospheric electric field, temperature, methane concentration, and other observation parameters, and further carried out indoor gas–solid friction tests. The study shows that methane gas (the concentration of methane at the centralized leakage point is higher than 10,000 ppm) in the permafrost degradation area will release rapidly in spring, and friction with soil, surface plant residues, and water vapor will accelerate atmospheric convection and generate electrostatic and atmospheric electrodischarge phenomena on the surface. The electrostatic and atmospheric electrodischarge accumulated on the surface will further ignite the combustibles near the surface, such as methane gas and plant residues. Therefore, the gradual release of methane gas into the air promotes the feedback mechanism of lightning–wildfire–vegetation, and increases the risk of wildfire in degraded permafrost areas through frictional electrification (i.e., electrostatic and atmospheric electrodischarge). [ABSTRACT FROM AUTHOR]

Socks are an important part of our clothing used in everyday activities. In order to ensure thermal comfort during wear in cool outdoor or indoor conditions, and for health improvement, socks must have effective thermoregulation properties. Chemical far-infrared (FIR) fibers with different bio-ceramic compounds incorporated into socks' structures can provide an improved thermoregulation effect to the wearer of the socks. Fibers with silver and carbon additives incorporated in their structures can also affect the thermoregulation properties of socks. Moreover, these conductive additives avoid the unpleasant effect of static electricity of socks. The main parts of the different investigated structures of the socks were made in a plush pattern. The plush loops were formed by using functional Resistex® Bioceramic, Shieldex® and two modifications of Nega-Stat® fiber yarns. The main thermal comfort (thermal efficiency, microclimate and heat exchange temperatures, thermal resistance, water vapor permeability) and electrostatic (surface and vertical resistances, shielding factor, half time decay of charge) properties of the socks were investigated. Based on the obtained results of the thermal comfort and electrostatic characteristics of the different investigated structures of socks, the optimal static dissipative (half-time decay <0.01 s, shielding factor—0.96) plush knitting structure with 55% Resistex® Bioceramic and 31% bicomponent Nega-Stat® P210 fibers yarns was selected. Comparing the control sample without FIR and the knitted structure with conductive additives, we can draw the conclusion that the heat retention capability of the selected socks was improved by 1.5 °C and the temperature of their created microclimate was improved by 2 °C. [ABSTRACT FROM AUTHOR]

GTP-binding proteins are essential molecular switches that regulate a wide range of cellular processes. Their function relies on the specific recognition and binding of guanine within their binding pockets. This study aims to elucidate the molecular determinants underlying this recognition. A large-scale data mining of the Protein Data Bank yielded 298 GTP-binding protein complexes, which provided a structural foundation for a systematic analysis of the intermolecular interactions that are responsible for the molecular recognition of guanine in proteins. It was found that multiple modes of non-bonded interactions including hydrogen bonding, cation-π interactions, and π-π stacking interactions are employed by GTP-binding proteins for binding. Subsequently, the strengths of non-bonded interaction energies between guanine and its surrounding protein residues were quantified by means of the double-hybrid DFT method B2PLYP-D3/cc-pVDZ. Hydrogen bonds, particularly those involving the N2 and O6 atoms of guanine, confer specificity to guanine recognition. Cation-π interactions between the guanine ring and basic residues (Lys and Arg) provide significant electrostatic stabilization. π-π stacking interactions with aromatic residues (Phe, Tyr, and Trp) further contribute to the overall binding affinity. This synergistic interplay of multiple interaction modes enables GTP-binding proteins to achieve high specificity and stability in guanine recognition, ultimately underpinning their crucial roles in cellular signaling and regulation. Notably, the NKXD motif, while historically considered crucial for guanine binding in GTP-binding proteins, is not universally required. Our study revealed significant variability in hydrogen bonding patterns, with many proteins lacking the NKXD motif but still effectively binding guanine through alternative arrangements of interacting residues.

The angiotensin-converting enzyme-2 (ACE2) is a transmembrane glycoprotein, consisting of two segments: a large carboxypeptidase catalytic domain and a small transmembrane collectrin-like segment. This protein plays an essential role in blood pressure regulation, transforming the peptides angiotensin-I and angiotensin-II (vasoconstrictors) into angiotensin-1-9 and angiotensin-1-7 (vasodilators). During the COVID-19 pandemic, ACE2 became best known as the receptor of the S-protein of SARS-CoV-2 coronavirus. The purpose of the following research is to reconstruct the 3D structure of the catalytic domain of the rabbit enzyme rACE2 using its primary amino acid sequence, and then to compare it with the human analog hACE2. For this purpose, we have calculated the electric properties and thermodynamic stability of the two protein globules employing computer programs for protein electrostatics. The analysis of the amino acid content and sequence demonstrates an 85% identity between the two polypeptide chains. The 3D alignment of the catalytic domains of the two enzymes shows coincidence of the α-helix segments, and a small difference in two unstructured segments of the chain. The electric charge of the catalytic domain of rACE2, determined by 70 positively chargeable amino acid residues, 114 negatively chargeable ones, and two positive charges of the Zn 2+ atom in the active center exceeds that of hACE2 by one positively and four negatively chargeable groups; however, in 3D conformation, their isoelectric points pI 5.21 coincide. The surface electrostatic potential is similarly distributed on the surface of the two catalytic globules, but it strongly depends on the pH of the extracellular medium: it is almost positive at pH 5.0 but strongly negative at pH 7.4. The pH dependence of the electrostatic component of the free energy discloses that the 3D structure of the two enzymes is maximally stable at pH 6.5. The high similarity in the 3D structure, as well as in the electrostatic and thermodynamic properties, suggests that rabbit can be successfully used as an animal model to study blood pressure regulation and coronavirus infection, and the results can be extrapolated to humans.

Confining protons into an enclosed carbon cage is expected to give rise to unique electronic properties for both the inner proton and the outer cage. In this work, we systematically investigated the geometric and electronic structures of cationic X + @C 60 (X + = H + , H 3 O + , and NH 4 + ), and their corresponding neutral species (X = H 2 O, NH 3 ), by quantum chemical density functional theory calculations. We show that C 60 can trap H 2 O, NH 3 , H 3 O + and NH 4 + at the cage center and only slightly influence their geometries. The single proton clings to the inner wall of C 60 , forming a C-H chemical bond. The encapsulated neutral species almost do not change the electronic structure of the C 60 , while the internal cations have obvious effects. The charge transfer effect from the inner species to the C 60 cage was found for all X@C 60 (X = H 2 O, NH 3 ) (about 0.0 e), X + @C 60 (X + = H 3 O + , NH 4 + ) (about 0.5 e) and H + @C 60 (about 1.0 e) systems. Encapsulating different forms of protons also regulates the fundamental physico-chemical properties of the hollow C 60 , such as the HOMO-LUMO gaps, infrared spectra, and electrostatic potential, etc., which are discussed in detail. These findings provide a theoretical insight into protons' applications, especially in energy.

The supramolecular structure of the crystal products- N -[2-chloro-2-(silatranyl)ethyl]-4-nitro-benzenesulfonamide 4d and N -chloro- N -[2-chloro-1-(silatran-1-yl-methyl)ethyl]benzene-sulfonamide 5a was established by X-ray diffraction analysis data, FTIR spectroscopy and DFT quantum chemical calculations. Their crystal lattice is formed by cyclic dimers with intermolecular hydrogen NH∙∙∙O-Si bonds and CH∙∙∙O=S short contacts. The distribution of electron density in the monomers was determined using quantum chemical calculations of their molecular electrostatic potential (MESP) in an isolated state (in gas) and in a polar medium. The transition from covalent N-Si bonds in crystal compounds and polar medium to non-covalent N∙∙∙Si bonds happened while performing the calculations on the monomer molecules and their dimers in gas. The effect of intermolecular interactions on the strength of the N-Si and N∙∙∙Si bonds in molecules was evaluated through calculations of their complexes with H 2 O and DMSO.

The deposition of amyloid β-protein (Aβ) in the brain is the main pathogenesis of Alzheimer's disease (AD). The development of potent inhibitors against Aβ aggregation is one of the effective strategies to combat AD. Endogenous transthyretin (TTR) can inhibit Aβ fibrillization via hydrophobic interactions, but its weak inhibitory potency hinders its application in AD therapy. Here, different recombinant TTRs were designed by cationic surface charge engineering. Compared with TTR, all positively charged recombinant TTRs showed enhanced capability in inhibiting Aβ aggregation, especially the recombinant protein obtained by mutating the acidic amino acid in TTR to arginine (TTR-nR) exhibited excellent inhibitory effect. Among them, TTR-7R remarkably increased the inhibitory potency against Aβ, which could effectively inhibit Aβ 40 fibrillization at a very low concentration (0.5 μM). In addition, TTR-7R increased cultured cell viability from 62% to 89%, scavenged amyloid plaques in AD nematodes, and prolonged nematode lifespan by 5 d at 2 μM. Thermodynamic studies demonstrated that TTR-7R, enriching in positive charges, presented hydrophobic interactions and enhanced electrostatic interactions with Aβ 40 , leading to a significantly enhanced inhibitory capacity of TTR-7R. The research provided insights into the development of efficient recombinant protein inhibitors for AD treatment.

At present, the effects of environmental electromagnetic irradiation on the metabolism of organisms have attracted extensive attention, but the mechanism is still not clear. D-glucose plays an important role in the metabolism of organisms. In this work, the change in the optical rotation of D-glucose solution under an electrostatic field is measured experimentally, so as to explain the mechanism of the electric field-induced biological effect. The experimental results show that the electrostatic field can alter the optical rotation of D-glucose solution at different temperatures. Under the different strengths of electrostatic field, the specific rotation of D-glucose solution increases at different temperatures; the maximum increase can reach 2.07%, but the effect of temperature and electric field strength on the rotation increment is nonlinear and very complex. Further, it turns out that the proportion of α-D-glucose in solution increases by up to 3.25% under the electrostatic field, while the proportion of β-D-glucose decreases by as much as 1.75%. The experimental study confirms that electrostatic field can change the proportion of two conformation molecules (α and β-D-glucose) in D-glucose solution, which can provide a novel explanation for the mechanism of the electric field-induced biological effect.

Non-thermal plasma (NTP) synergistic anticancer strategies are a current hotspot of interest at the intersection of plasma biomedicine. Melittin (MEL) has been shown to inhibit cancer in many malignant tumors; however, its clinical application is controversial. Therefore, the transmembrane process and mechanism of MEL activity in different cell systems were studied and the combination of MEL and NTP was proposed in this paper. The results showed that the electrostatic attraction between MEL and the lipid bilayer contributes to the stable orientation of MEL on the membrane surface. In addition, sialic acid overexpression affects the degree to which MEL binds the membrane system and the stability of the membrane structure. The use of NTP to reduce the dosage of MEL and its related nonspecific cytolysis activity has certain clinical application value. The results of this study provide theoretical support for improving the clinical applicability of MEL and contribute to the further development of plasma biomedicine.

Background: Bioaerosols can represent a danger to health. During SARS-CoV-2 pandemic, portable devices were used in different environments and considered a valuable prevention tool. This study has evaluated the effectiveness of the air treatment device "AEROK 1.0 ® " in reducing microbial, particulate, and pollen airborne contamination indoors, during normal activity., Methods: In an administrative room, airborne microbial contamination was measured using active (DUOSAS 360 and MD8) and passive sampling; a particle counter was used to evaluate particle concentrations; a Hirst-type pollen trap was used to assess airborne pollen and Alternaria spores. Statistical analysis was performed using SPSS 26.0; p values < 0.05 were considered statistically significant., Results: The airborne bacterial contamination assessed by the two different samplers decreased by 56% and 69%, respectively. The airborne bacterial contamination assessed by passive sampling decreased by 44%. For fungi, the reduction was 39% by active sampling. Airborne particles (diameters ≥ 1.0, 2.0 μm) and the ratio of indoor/outdoor concentrations of total pollen and Alternaria spp. spores significantly decreased., Conclusions: The results highlight the effectiveness of AEROK 1.0 ® in reducing airborne contamination. The approach carried out represents a contribution to the definition of a standardized model for evaluating the effectiveness of devices to be used for air disinfection.

The chemical gating of gap junction channels is mediated by cytosolic calcium (Ca 2+ i ) at concentrations ([Ca 2+ ] i ) ranging from high nanomolar (nM) to low micromolar (µM) range. Since the proteins of gap junctions, connexins/innexins, lack high-affinity Ca 2+ -binding sites, most likely gating is mediated by a Ca 2+ -binding protein, calmodulin (CaM) being the best candidate. Indeed, the role of Ca 2+ -CaM in gating is well supported by studies that have tested CaM blockers, CaM expression inhibition, testing of CaM mutants, co-localization of CaM and connexins, existence of CaM-binding sites in connexins/innexins, and expression of connexins (Cx) mutants, among others. Based on these data, since 2000, we have published a Ca 2+ -CaM-cork gating model. Despite convincing evidence for the Ca 2+ -CaM role in gating, a recent study has proposed an alternative gating model that would involve a direct electrostatic Ca 2+ -connexin interaction. However, this study, which tested the effect of unphysiologically high [Ca 2+ ] i on the structure of isolated junctions, reported that neither changes in the channel's pore diameter nor connexin conformational changes are present, in spite of exposure of isolated gap junctions to [Ca 2+ ] i as high at the 20 mM. In conclusion, data generated in the past four decades by multiple experimental approaches have clearly demonstrated the direct role of Ca 2+ -CaM in gap junction channel gating.

The hydrophobic effect is the main factor that drives the folding of polypeptide chains. In this study, we have examined the influence of the hydrophobic effect in the context of the main mechanical forces approach, mainly in relation to the establishment of specific interplays, such as hydrophobic and CH-π cloud interactions. By adopting three oligopeptides as model systems to assess folding features, we demonstrate herein that these finely tuned interactions dominate over electrostatic interactions, including H-bonds and electrostatic attractions/repulsions. The folding mechanism analysed here demonstrates cooperation at the single-residue level, for which we propose the terminology of "single residues cooperative folding". Overall, hydrophobic and CH-π cloud interactions produce the main output of the hydrophobic effect and govern the folding mechanism, as demonstrated in this study with small polypeptide chains, which in turn represent the main secondary structures in proteins.

The Coulomb coupling between transition densities of the pigments in photosynthetic pigment-protein complexes, termed excitonic coupling, is a key factor for the description of optical spectra and energy transfer. A challenging question is the quantification of the screening of the excitonic coupling by the optical polarizability of the environment. We use the equivalence between the sophisticated quantum chemical polarizable continuum (PCM) model and the simple electrostatic Poisson-TrEsp approach to analyze the distance and orientation dependence of the dielectric screening between chlorophylls in photosystem I trimers. On the basis of these calculations we find that the vacuum couplings Vmn(0) and the couplings in the dielectric medium Vmn=fmnVmn(0) are related by the empirical screening factor fmn=0.60+39.6θ(|κmn|-1.17)exp(-0.56Rmn/Å), where κmn is the usual orientational factor of the dipole-dipole coupling between the pigments, Rmn is the center-to-center distance, and the Heaviside-function θ(|κmn|-1.17) ensures that the exponential distance dependence only contributes for in-line type dipole geometries. We are confident that the present expression can be applied also to other pigment-protein complexes with chlorophyll or related pigments of similar shape. The variance between the Poisson-TrEsp and the approximate coupling values is found to decrease by a factor of 8 and 3-4 using the present expression, instead of an exponential distance dependent or constant screening factor, respectively, assumed previously in the literature.

The synapse is a piece of information transfer machinery replacing the electrical conduction of nerve impulses at the end of the neuron. Like many biological mechanisms, its functioning is heavily affected by time constraints. The solution selected by evolution is based on chemical communication that, in theory, cannot compete with the speed of nerve conduction. Nevertheless, biochemical and biophysical compensation mechanisms mitigate this intrinsic weakness: (i) through the high concentrations of neurotransmitters inside the synaptic vesicles; (ii) through the concentration of neurotransmitter receptors in lipid rafts, which are signaling platforms; indeed, the presence of raft lipids, such as gangliosides and cholesterol, allows a fine tuning of synaptic receptors by these lipids; (iii) through the negative electrical charges of the gangliosides, which generate an attractive (for cationic neurotransmitters, such as serotonin) or repulsive (for anionic neurotransmitters, such as glutamate) electric field. This electric field controls the flow of glutamate in the tripartite synapse involving pre- and post-synaptic neurons and the astrocyte. Changes in the expression of brain gangliosides can disrupt the functioning of the glutamatergic synapse, causing fatal diseases, such as Rett syndrome. In this review, we propose an in-depth analysis of the role of gangliosides in the glutamatergic synapse, highlighting the primordial and generally overlooked role played by the electric field of synaptic gangliosides.

Accurate calculation of non-covalent interaction energies in nucleotides is crucial for understanding the driving forces governing nucleic acid structure and function, as well as developing advanced molecular mechanics forcefields or machine learning potentials tailored to nucleic acids. Here, we dissect the nucleotides' structure into three main constituents: nucleobases (A, G, C, T, and U), sugar moieties (ribose and deoxyribose), and phosphate group. The interactions among these fragments and between fragments and water were analyzed. Different quantum mechanical methods were compared for their accuracy in capturing the interaction energy. The non-covalent interaction energy was decomposed into electrostatics, exchange-repulsion, dispersion, and induction using two ab initio methods: Symmetry-Adapted Perturbation Theory (SAPT) and Absolutely Localized Molecular Orbitals (ALMO). These calculations provide a benchmark for different QM methods, in addition to providing a valuable understanding of the roles of various intermolecular forces in hydrogen bonding and aromatic stacking. With SAPT, a higher theory level and/or larger basis set did not necessarily give more accuracy. It is hard to know which combination would be best for a given system. In contrast, ALMO EDA2 did not show dependence on theory level or basis set; additionally, it is faster.

The noncovalent chalcogen interaction between SO 2 /SO 3 and diazines was studied through a dispersion-corrected DFT Kohn-Sham molecular orbital together with quantitative energy decomposition analyses. For this, supramolecular circular chains of up to 12 molecules were built with the aim of checking the capability of diazine molecules to detect SO 2 /SO 3 compounds within the atmosphere. Trends in the interaction energies with the increasing number of molecules are mainly determined by the Pauli steric repulsion involved in these σ-hole/π-hole interactions. But more importantly, despite the assumed electrostatic nature of the involved interactions, the covalent component also plays a determinant role in its strength in the involved chalcogen bonds. Noticeably, π-hole interactions are supported by the charge transfer from diazines to SO 2 /SO 3 molecules. Interaction energies in these supramolecular complexes are not only determined by the S···N bond lengths but attractive electrostatic and orbital interactions also determine the trends. These results should allow us to establish the fundamental characteristics of chalcogen bonding based on its strength and nature, which is of relevance for the capture of sulfur oxides.

Montmorillonite (MM) crystal nanoplates acquire anticancer properties when coated with the mitochondrial protein cytochrome c (cytC) due to the cancer cells' capability to phagocytize cytC-MM colloid particles. The introduced exogenous cytC initiates apoptosis: an irreversible cascade of biochemical reactions leading to cell death. In the present research, we investigate the organization of the cytC layer on the MM surface by employing physicochemical and computer methods-microelectrophoresis, static, and electric light scattering-to study cytC adsorption on the MM surface, and protein electrostatics and docking to calculate the local electric potential and Gibbs free energy of interacting protein globules. The found protein concentration dependence of the adsorbed cytC quantity is nonlinear, manifesting a positive cooperative effect that emerges when the adsorbed cytC globules occupy more than one-third of the MM surface. Computer analysis reveals that the cooperative effect is caused by the formation of protein associates in which the cytC globules are oriented with oppositely charged surfaces. The formation of dimers and trimers is accompanied by a strong reduction in the electrostatic component of the Gibbs free energy of protein association, while the van der Waals component plays a secondary role.

Mineral oils and synthetic and natural esters are the predominant insulating liquids in electrical equipment. Structure-activity relationship models to predict the key properties of pure insulating liquids, including pulse breakdown strengths, AC breakdown voltages, dielectric constants, flash points, and kinematic viscosities, have been proposed for the first time. Dependence of the specific properties on the molecular structures has been illustrated quantitatively in terms of surface area, statistical total variance, and average deviation of positive and negative electrostatic potentials, as augmented by molecular weight, volume, and ovality. Moreover, the individual contribution of the functional groups to viscosity has been revealed by an additive approach. The predicted properties are in good agreement with the experimental data. The present theoretical work provides new insights on the development of novel dielectric fluids.

The construction of peptides to mimic heterogeneous proteins such as type I collagen plays a pivotal role in deciphering their function and pathogenesis. However, progress in the field has been severely hampered by the lack of capability to create stable heterotrimers with desired functional sequences and without the effect of homotrimers. We have herein developed a set of triblock peptides that can assemble into collagen mimetic heterotrimers with desired amino acids and are free from the interference of homotrimers. The triblock peptides comprise a central collagen-like block and two oppositely charged N-/C-terminal blocks, which display inherent incompetency of homotrimer formation. The favorable electrostatic attraction between two paired triblock peptides with complementary terminal charged sequences promptly leads to stable heterotrimers with controlled chain composition. The independence of the collagen-like block from the two terminal blocks endows this system with the adaptability to incorporate desired amino acid sequences while maintaining the heterotrimer structure. The triblock peptides provide a versatile and robust tool to mimic the composition and function of heterotrimer collagen and may have great potential in the design of innovative peptides mimicking heterogeneous proteins.

The bottom-up fabrication of supramolecular and self-assembly on various substrates has become an extremely relevant goal to achieve prospects in the development of nanodevices for electronic circuitry or sensors. One of the branches of this field is the self-assembly of functional molecular components driven through non-covalent interactions on the surfaces, such as van der Waals (vdW) interactions, hydrogen bonding (HB), electrostatic interactions, etc., allowing the controlled design of nanostructures that can satisfy the requirements of nanoengineering concepts. In this context, non-covalent interactions present opportunities that have been previously explored in several molecular systems adsorbed on surfaces, primarily due to their highly directional nature which facilitates the formation of well-ordered structures. Herein, we review a series of research works by combining STM (scanning tunneling microscopy) with theoretical calculations, to reveal the processes used in the area of self-assembly driven by molecule Landers equipped with functional groups on the metallic surfaces. Combining these processes is necessary for researchers to advance the self-assembly of supramolecular architectures driven by multiple non-covalent interactions on solid surfaces.

This study reveals a new non-covalent interaction called a π-hole halogen bond, which is directional and potentially non-linear compared to its sister analog (σ-hole halogen bond). A π-hole is shown here to be observed on the surface of halogen in halogenated molecules, which can be tempered to display the aptness to form a π-hole halogen bond with a series of electron density-rich sites (Lewis bases) hosted individually by 32 other partner molecules. The [MP2/aug-cc-pVTZ] level characteristics of the π-hole halogen bonds in 33 binary complexes obtained from the charge density approaches (quantum theory of intramolecular atoms, molecular electrostatic surface potential, independent gradient model (IGM- δg inter )), intermolecular geometries and energies, and second-order hyperconjugative charge transfer analyses are discussed, which are similar to other non-covalent interactions. That a π-hole can be observed on halogen in halogenated molecules is substantiated by experimentally reported crystals documented in the Cambridge Crystal Structure Database. The importance of the π-hole halogen bond in the design and growth of chemical systems in synthetic chemistry, crystallography, and crystal engineering is yet to be fully explicated.

Ca 2+ binding to the ubiquitous Ca 2+ sensing protein calmodulin (CaM) activates the intermediate conductance Ca 2+ -activated SK4 channel. Potential hydrophilic pockets for CaM binding have been identified at the intracellular HA and HB helices in the C-terminal of SK4 from the three published cryo-EM structures of SK4. Single charge reversal substitutions at either site, significantly weakened the pull-down of SK4 by CaM wild-type (CaM), and decreased the TRAM-34 sensitive outward K + current densities in native HEK293T cells when compared with SK4 WT measured under the same conditions. Only the doubly substituted SK4 R352D/R355D (HB helix) obliterated the CaM-mediated pull-down and thwarted outward K + currents. However, overexpression of CaM E84K/E87K, which had been predicted to face the arginine doublet, restored the CaM-mediated pull-down of SK4 R352D/R355D and normalized its whole-cell current density. Virtual analysis of the putative salt bridges supports a unique role for the positively charged arginine doublet at the HB helix into anchoring the interaction with the negatively charged CaM glutamate 84 and 87 CaM. Our findings underscore the unique contribution of electrostatic interactions in carrying CaM binding onto SK4 and support the role of the C-terminal HB helix to the Ca 2+ -dependent gating process.

The evolutionary interplay between predator and prey has significantly shaped the development of snake venom, a critical adaptation for subduing prey. This arms race has spurred the diversification of the components of venom and the corresponding emergence of resistance mechanisms in the prey and predators of venomous snakes. Our study investigates the molecular basis of venom resistance in pythons, focusing on electrostatic charge repulsion as a defense against α-neurotoxins binding to the alpha-1 subunit of the postsynaptic nicotinic acetylcholine receptor. Through phylogenetic and bioactivity analyses of orthosteric site sequences from various python species, we explore the prevalence and evolution of amino acid substitutions that confer resistance by electrostatic repulsion, which initially evolved in response to predatory pressure by Naja (cobra) species (which occurs across Africa and Asia). The small African species Python regius retains the two resistance-conferring lysines (positions 189 and 191) of the ancestral Python genus, conferring resistance to sympatric Naja venoms. This differed from the giant African species Python sebae , which has secondarily lost one of these lysines, potentially due to its rapid growth out of the prey size range of sympatric Naja species. In contrast, the two Asian species Python brongersmai (small) and Python bivittatus (giant) share an identical orthosteric site, which exhibits the highest degree of resistance, attributed to three lysine residues in the orthosteric sites. One of these lysines (at orthosteric position 195) evolved in the last common ancestor of these two species, which may reflect an adaptive response to increased predation pressures from the sympatric α-neurotoxic snake-eating genus Ophiophagus (King Cobras) in Asia. All these terrestrial Python species, however, were less neurotoxin-susceptible than pythons in other genera which have evolved under different predatory pressure as: the Asian species Malayopython reticulatus which is arboreal as neonates and juveniles before rapidly reaching sizes as terrestrial adults too large for sympatric Ophiophagus species to consider as prey; and the terrestrial Australian species Aspidites melanocephalus which occupies a niche, devoid of selection pressure from α-neurotoxic predatory snakes. Our findings underline the importance of positive selection in the evolution of venom resistance and suggest a complex evolutionary history involving both conserved traits and secondary evolution. This study enhances our understanding of the molecular adaptations that enable pythons to survive in environments laden with venomous threats and offers insights into the ongoing co-evolution between venomous snakes and their prey.

The contagiousness of SARS-CoV-2 β-coronavirus is determined by the virus-receptor electrostatic association of its positively charged spike (S) protein with the negatively charged angiotensin converting enzyme-2 (ACE2 receptor) of the epithelial cells. If some mutations occur, the electrostatic potential on the surface of the receptor-binding domain (RBD) could be altered, and the S-ACE2 association could become stronger or weaker. The aim of the current research is to investigate whether point mutations can noticeably alter the electrostatic potential on the RBD and the 3D stability of the S1-subunit of the S-protein. For this purpose, 15 mutants with different hydrophilicity and electric charge (positive, negative, or uncharged) of the substituted and substituting amino acid residues, located on the RBD at the S1-ACE2 interface, are selected, and the 3D structure of the S1-subunit is reconstructed on the base of the crystallographic structure of the S-protein of the wild-type strain and the amino acid sequence of the unfolded polypeptide chain of the mutants. Then, the Gibbs free energy of folding, isoelectric point, and pH-dependent surface electrostatic potential of the S1-subunit are computed using programs for protein electrostatics. The results show alterations in the local electrostatic potential in the vicinity of the mutant amino acid residue, which can influence the S-ACE2 association. This approach allows prediction of the relative infectivity, transmissibility, and contagiousness (at equal social immune status) of new SARS-CoV-2 mutants by reconstruction of the 3D structure of the S1-subunit and calculation of the surface electrostatic potential.

Three-dimensional (3D) hepatocyte models have become a research hotspot for evaluating drug metabolism and hepatotoxicity. Compared to two-dimensional (2D) cultures, 3D cultures are better at mimicking the morphology and microenvironment of hepatocytes in vivo. However, commonly used 3D culture techniques are not suitable for high-throughput drug screening (HTS) due to their high cost, complex handling, and inability to simulate cell-extracellular matrix (ECM) interactions. This article describes a method for rapid and reproducible 3D cell cultures with ECM-cell interactions based on 3D culture instrumentation to provide more efficient HTS. We developed a microsphere preparation based on a high-voltage electrostatic (HVE) field and used sodium alginate- and collagen-based hydrogels as scaffolds for 3D cultures of HepG2 cells. The microsphere-generating device enables the rapid and reproducible preparation of bioactive hydrogel microspheres. This 3D culture system exhibited better cell viability, heterogeneity, and drug-metabolizing activity than 2D and other 3D culture models, and the long-term culture characteristics of this system make it suitable for predicting long-term liver toxicity. This system improves the overall applicability of HepG2 spheroids in safety assessment studies, and this simple and controllable high-throughput-compatible method shows potential for use in drug toxicity screening assays and mechanistic studies.

Protein-nanoparticle hybridization can ideally lead to novel biological entities characterized by emerging properties that can sensibly differ from those of the parent components. Herein, the effect of ionic strength on the biological functions of recombinant His-tagged spermine oxidase (i.e., SMOX) was studied for the first time. Moreover, SMOX was integrated into colloidal surface active maghemite nanoparticles (SAMNs) via direct self-assembly, leading to a biologically active nano-enzyme (i.e., SAMN@SMOX). The hybrid was subjected to an in-depth chemical-physical characterization, highlighting the fact that the protein structure was perfectly preserved. The catalytic activity of the nanostructured hybrid (SAMN@SMOX) was assessed by extracting the kinetics parameters using spermine as a substrate and compared to the soluble enzyme as a function of ionic strength. The results revealed that the catalytic function was dominated by electrostatic interactions and that they were drastically modified upon hybridization with colloidal ɣ-Fe 2 O 3 . The fact that the affinity of SMOX toward spermine was significantly higher for the nanohybrid at low salinity is noteworthy. The present study supports the vision of using protein-nanoparticle conjugation as a means to modulate biological functions.

In order to enhance the maximum power point tracking (MPPT) speed of solar generators, offline calculated maximum power line (MPL) is often used as a feed-forward signal added to the output of MPPT controller. MPL is nonlinear static electrical characteristic of renewable energy generators connecting all the maximum power points for given temperature. In this letter, electrical side MPL is derived for a typical wind turbine generator (WTG). It is shown that MPLs of solar and wind generators possess similar structure, supporting the similarity between the two energy conversion processes. [ABSTRACT FROM AUTHOR]

In this study, the effect of corrosion on the static behavior of stud shear connectors was investigated. An innovative test setup for single stud shear connectors was designed and established. Two series of specimens having different stud diameters were fabricated and tested. The test specimens were firstly corroded to different corrosion rates by the electronic accelerating method. Static loading tests were then performed to obtain the load-slip curves and ultimate strengths of the corroded test specimens. The actual corrosion rates were measured from the studs obtained from the tested specimens. The test results were compared with the push out test specimens having similar corrosion rates. It is shown that the test results obtained from the single stud shear connectors are conservative compared with the corroded push test specimens, which prove the validation of the single stud shear connector test method. The effect of corrosion on the behavior of stud shear connectors was also presented. [ABSTRACT FROM AUTHOR]

The high propensity of protons to stay at interfaces has attracted much attention over the decades. It enables long-range interfacial proton diffusion without relying on titratable residues or electrostatic attraction. As a result, various phenomena manifest themselves, ranging from spillover in material sciences to local proton circuits between proton pumps and ATP synthases in bioenergetics. In an attempt to replace all existing theoretical and experimental insight into the origin of protons' preference for interfaces, TELP, the "Transmembrane Electrostatically-Localized Protons" hypothesis, has been proposed. The TELP hypothesis envisions static H + and OH - layers on opposite sides of interfaces that are up to 75 µm thick. Yet, the separation at which the electrostatic interaction between two elementary charges is comparable in magnitude to the thermal energy is more than two orders of magnitude smaller and, as a result, the H + and OH - layers cannot mutually stabilize each other, rendering proton accumulation at the interface energetically unfavorable. We show that (i) the law of electroneutrality, (ii) Fick's law of diffusion, and (iii) Coulomb's law prevail. Using them does not hinder but helps to interpret previously published experimental results, and also helps us understand the high entropy release barrier enabling long-range proton diffusion along the membrane surface.

In recent years, the non-covalent interactions between chalcogen centers have aroused substantial research interest because of their potential applications in organocatalysis, materials science, drug design, biological systems, crystal engineering, and molecular recognition. However, studies on π-hole-type chalcogen ∙∙∙ chalcogen interactions are scarcely reported in the literature. Herein, the π-hole-type intermolecular chalcogen ∙∙∙ chalcogen interactions in the model complexes formed between XO 2 (X = S, Se, Te) and CH 3 YCH 3 (Y = O, S, Se, Te) were systematically studied by using quantum chemical computations. The model complexes are stabilized via one primary X ∙∙∙ Y chalcogen bond (ChB) and the secondary C-H ∙∙∙ O hydrogen bonds. The binding energies of the studied complexes are in the range of -21.6~-60.4 kJ/mol. The X ∙∙∙ Y distances are significantly smaller than the sum of the van der Waals radii of the corresponding two atoms. The X ∙∙∙ Y ChBs in all the studied complexes except for the SO 2 ∙∙∙ CH 3 OCH 3 complex are strong in strength and display a partial covalent character revealed by conducting the quantum theory of atoms in molecules (QTAIM), a non-covalent interaction plot (NCIplot), and natural bond orbital (NBO) analyses. The symmetry-adapted perturbation theory (SAPT) analysis discloses that the X ∙∙∙ Y ChBs are primarily dominated by the electrostatic component.

In this paper, we theoretically investigated spectral physics on Cu(III) complexes formed by the oxidative addition of α-haloacetonitrile to ionic and neutral Cu(I) complexes, stimulated by recent experimental reports. Firstly, the electronic structures of reactants of α-haloacetonitrile and neutral Cu(I) and two kinds of products of Cu(III) complexes are visualized with the density of state (DOS) and orbital energy levels of HOMO and LUMO. The visually manifested static and dynamic polarizability as well as the first hyperpolarizability are employed to reveal the vibrational modes of the normal and resonance Raman spectra of two Cu(III) complexes. The nuclear magnetic resonance (NMR) spectra are not only used to identify the reactants and products but also to distinguish between two Cu(III) complexes. The charge difference density (CDD) reveals intramolecular charge transfer in electronic transitions in optical absorption spectra. The CDDs in fluorescence visually reveal electron-hole recombination. Our results promote a deeper understanding of the physical mechanism of stable Cu(III) produced by the oxidative addition of an alkyl halide.

In this study, a series of electron donor (-NH 2 , -NMe 2 and - t Bu) and electron-withdrawing substituents (-F, -CN and -NO 2 ) were used to tune the nucleophilicity or electrophilicity of a series of square planar Ni 2+ , Pd 2+ and Pt 2+ malonate coordination complexes towards a pentafluoroiodobenzene and a pyridine molecule. In addition, Bader's theory of atoms in molecules (AIM), noncovalent interaction plot (NCIplot), molecular electrostatic potential (MEP) surface and natural bond orbital (NBO) analyses at the PBE0-D3/def2-TZVP level of theory were carried out to characterize and discriminate the role of the metal atom in the noncovalent complexes studied herein. We hope that the results reported herein may serve to expand the current knowledge regarding these metals in the fields of crystal engineering and supramolecular chemistry.

Lysophosphatidic acid (LPA) is a promising biomarker candidate to screen for ovarian cancer (OC) and potentially stratify and treat patients according to disease stage. LPA is known to target the actin-binding protein gelsolin which is a key regulator of actin filament assembly. Previous studies have shown that the phosphate headgroup of LPA alone is inadequate to bind to the short chain of amino acids in gelsolin known as the PIP 2 -binding domain. Thus, the molecular-level detail of the mechanism of LPA binding is poorly understood. Here, we model LPA binding to the PIP 2 -binding domain of gelsolin in the gelsolin-actin complex through extensive ten-microsecond atomistic molecular dynamics (MD) simulations. We predict that LPA binding causes a local conformational rearrangement due to LPA interactions with both gelsolin and actin residues. These conformational changes are a result of the amphipathic nature of LPA, where the anionic phosphate, polar glycerol and ester groups, and lipophilic aliphatic tail mediate LPA binding via charged electrostatic, hydrogen bonding, and van der Waals interactions. The negatively-charged LPA headgroup binds to the PIP 2 -binding domain of gelsolin-actin while its hydrophobic tail is inserted into actin, creating a strong LPA-insertion pocket that weakens the gelsolin-actin interface. The computed structure, dynamics, and energetics of the ternary gelsolin-LPA-actin complex confirms that a quantitative OC assay is possible based on LPA-triggered actin release from the gelsolin-actin complex.

Previous experimental investigations have established the indispensability of the C-terminal Lys-Arg residues in the toxic activity of the AapA1 toxin protein. AapA1 is classified as a type I toxin-antitoxin (TA) bacterial toxin, and the precise impact of the C-terminal Lys-Arg residues on its structure and mechanism of action remains elusive. To address this knowledge gap, the present study employed molecular dynamics (MD) and enhanced sampling Well-tempered Two-dimensional Metadynamics (2D-MetaD) simulations to examine the behavior of the C-terminal Lys-Arg residues of truncated AapA1 toxin (AapA1-28) within the inner membrane of Escherichia coli . Specifically, the study focused on the elucidation of possible conformation states of AapA1-28 protein in POPE/POPG (3:1) bilayers and their interactions between the protein and POPE/POPG (3:1) bilayers. The findings of our investigation indicate that the AapA1-28 protein does not adopt a vertical orientation upon membrane insertion; rather, it assumes an angled conformation, with the side chain of Lys-23 directed toward the upper layer of the membrane. This non-transmembrane conformation of AapA1-28 protein impedes its ability to form pores within the membrane, resulting in reduced toxicity towards Escherichia coli . These results suggest that C-Terminal positively charged residues are essential for electrostatic binding to the negatively charged head group of bottom bilayer membrane, which stabilize the transmembrane conformation. These outcomes contribute to our comprehension of the impact of C-terminal charged residues on the structure and functionality of membrane-associated proteins, and provide an improved understanding of how protein sequence influences the antimicrobial effect.

The pathogenesis of influenza A viruses (IAVs) is influenced by several factors, including IAV strain origin and reassortment, tissue tropism and host type. While such factors were mostly investigated in the context of virus entry, fusion and replication, little is known about the viral-induced changes to the host lipid membranes which might be relevant in the context of virion assembly. In this work, we applied several biophysical fluorescence microscope techniques (i.e., Förster energy resonance transfer, generalized polarization imaging and scanning fluorescence correlation spectroscopy) to quantify the effect of infection by two IAV strains of different origin on the plasma membrane (PM) of avian and human cell lines. We found that IAV infection affects the membrane charge of the inner leaflet of the PM. Moreover, we showed that IAV infection impacts lipid-lipid interactions by decreasing membrane fluidity and increasing lipid packing. Because of such alterations, diffusive dynamics of membrane-associated proteins are hindered. Taken together, our results indicate that the infection of avian and human cell lines with IAV strains of different origins had similar effects on the biophysical properties of the PM.

Hydrogen bonds constitute a unique type of non-covalent interaction, with a critical role in biology. Until fairly recently, the canonical view held that these bonds occur between electronegative atoms, typically O and N, and that they are mostly electrostatic in nature. However, it is now understood that polarized C-H groups may also act as hydrogen bond donors in many systems, including biological macromolecules. First recognized from physical chemistry studies, C-H…X bonds were visualized with X-ray crystallography sixty years ago, although their true significance has only been recognized in the last few decades. This review traces the origins of the field and describes the occurrence and significance of the most important C-H…O bonds in proteins and nucleic acids.

The association of the S-protein of the SARS-CoV-2 beta coronavirus to ACE2 receptors of the human epithelial cells determines its contagiousness and pathogenicity. We computed the pH-dependent electric potential on the surface of the interacting globular proteins and pH-dependent Gibbs free energy at the association of the wild-type strain and the omicron variant. The calculated isoelectric points of the ACE2 receptor (pI 5.4) and the S-protein in trimeric form (pI 7.3, wild type), (pI 7.8, omicron variant), experimentally verified by isoelectric focusing, show that at pH 6-7, the S1-ACE2 association is conditioned by electrostatic attraction of the oppositely charged receptor and viral protein. The comparison of the local electrostatic potentials of the omicron variant and the wild-type strain shows that the point mutations alter the electrostatic potential in a relatively small area on the surface of the receptor-binding domain (RBD) of the S1 subunit. The appearance of seven charge-changing point mutations in RBD (equivalent to three additional positive charges) leads to a stronger S1-ACE2 association at pH 5.5 (typical for the respiratory tract) and a weaker one at pH 7.4 (characteristic of the blood plasma); this reveals the reason for the higher contagiousness but lower pathogenicity of the omicron variant in comparison to the wild-type strain.