Computational Study of Complex Formation between Hyaluronan Polymers and Polyarginine Peptides at Various Ratios.

Hyaluronic acid, a naturally occurring carbohydrate biopolymer in human tissues, finds wide application in cosmetics, medicine, and material science. Its anionic properties play a crucial role in its interaction with positively charged macromolecules and ions. Among these macromolecules, positively charged arginine molecules or polyarginine peptides demonstrate potential in drug delivery when complexed with hyaluronan. This study aimed to compare and elucidate the results of both experimental and computational investigations on the interactions between hyaluronic acid polymers and polyarginine peptides. Experimental findings revealed that by varying the length of polyarginine peptides and the molar ratio, it is possible to modulate the size, solubility, and stability of hyaluronan-arginine particles. To further explore these interactions, molecular dynamics simulations were conducted to model the complexes formed between hyaluronic acid polymers and arginine peptides. The simulations are considered in different molar ratios and lengths of polyarginine peptides. By analysis of the data, we successfully determined the shape and size of the resulting complexes. Additionally, we identified the primary driving forces behind complex formation and explained the observed variations in peptide interactions with hyaluronan.

Adsorption of Hexavalent Chromium Using Activated Carbon Produced from Sargassum ssp.: Comparison between Lab Experiments and Molecular Dynamics Simulations.

Adsorption is one of the most successful physicochemical approaches for removing heavy metal contaminants from polluted water. The use of residual biomass for the production of adsorbents has attracted a lot of attention due to its cheap price and environmentally friendly approach. The transformation of Sargassum-an invasive brown macroalga-into activated carbon (AC) via phosphoric acid thermochemical activation was explored in an effort to increase the value of Sargassum seaweed biomass. Several techniques (nitrogen adsorption, pHPZC, Boehm titration, FTIR and XPS) were used to characterize the physicochemical properties of the activated carbons. The SAC600 3/1 was predominantly microporous and mesoporous (39.6% and 60.4%, respectively) and revealed a high specific surface area (1695 m2·g-1). To serve as a comparison element, a commercial reference activated carbon with a large specific surface area (1900 m2·g-1) was also investigated. The influence of several parameters on the adsorption capacity of AC was studied: solution pH, solution temperature, contact time and Cr(VI) concentration. The best adsorption capacities were found at very acid (pH 2) solution pH and at lower temperatures. The adsorption kinetics of SAC600 3/1 fitted well a pseudo-second-order type 1 model and the adsorption isotherm was better described by a Jovanovic-Freundlich isotherm model. Molecular dynamics (MD) simulations confirmed the experimental results and determined that hydroxyl and carboxylate groups are the most influential functional groups in the adsorption process of chromium anions. MD simulations also showed that the addition of MgCl2 to the activated carbon surface before adsorption experiments, slightly increases the adsorption of HCrO4- and CrO42- anions. Finally, this theoretical study was experimentally validated obtaining an increase of 5.6% in chromium uptake.

Computational and experimental assessment of pH and specific ions on the solute solvent interactions of clay-biochar composites towards tetracycline adsorption: Implications on wastewater treatment.

Experimental and computational investigations have been conducted in this study to assess the influence of municipal waste pyrolyzed biochar impregnated clay composites on antibiotic removal as a material for wastewater treatment and simultaneous value-addition for waste. The surface potential (zeta potential) of the pristine biochar and composite samples are found to be within the range ~10 to ~ -40 mV in the pH range 2-10. The presence of different inorganic salt solutions influences the electrophoretic mobility of the dispersed phase in a suspension, as well as its zeta potential. In addition of Na+ salt solutions, the Na+ ions undergo electrostatic interaction with the negatively charged biochar samples and form a double layer at the interface of biochar and ionic salt solution. Molecular dynamics simulations have been employed to understand experimental findings, ions adsorption and solute-solvent interactions at the molecular level of two biochar B7 (seven benzene rings, one methoxy, one aldehyde and two hydroxyls groups) and B17 (seventeen benzene rings, one methoxy, two hydroxyls and two carboxylic acid groups) in salts aqueous solutions. The results confirm that hydroxyls and carboxylate groups of biochar are responsible for solute-solvent interactions. Successful removal of tetracycline antibiotics is observed with 26 mg/g maximum adsorption capacity with montmorillonite biochar composite. This study confirms that interactions between amide and hydroxyl groups of tetracycline with hydroxyl and carboxylate groups of biochar play the key role in the adsorption process. The solution pH and presence of different background electrolytes effectively influence the process of solute-solvent interactions as well as adsorption efficacy towards tetracycline adsorption.

Valorisation of agricultural waste derived biochars in aquaculture to remove organic micropollutants from water - experimental study and molecular dynamics simulations.

In this work, we evaluated the valorisation of agricultural waste materials by transforming coconut husks and shells, corncobs and rice straw into biochar for water treatment in aquaculture. We compared the biochars' suitability for removal of organic micropollutants (acetaminophen, oxytetracycline, tetracycline, enrofloxacin, atrazine, diuron and diclofenac) from surface water needed for aquaculture. The biochars were prepared by three methods ranging from inexpensive drum kilns (200 °C) to pyrolysis with biogasfication (350-750 °C). Overall, antibiotics tetracycline and enrofloxacin were the most strongly sorbed micropollutants, and coconut husk biochar prepared at 750 °C was the best sorbent material. Molecular Dynamics simulations indicated that the major sorption mechanism is via π-π stacking interactions and there is a possibility of multilayer sorption for some of the micropollutants. We observed, a strong impact of ionic strength (salinity), which is an important consideration in coastal aquaculture applications. High salinity decreased the sorption for antibiotics oxytetracycline, tetracycline and enrofloxacin but increased diclofenac, atrazine and diuron sorption. We considered coconut husk biochar produced in drum kilns the most practical option for biochar applications in small-scale coastal aquacultures in South Asia. Pilot trials of canal water filtration at an aquaculture farm revealed that micropollutant sorption by coconut husk biochar under real-world conditions might be 10-500 times less than observed in the laboratory studies. Even so, biochar amendment of sand enhanced the micropollutant retention, which may facilitate subsequent biodegradation and improve the quality of brackish surface water used for food production in coastal aquaculture.

Interactions between a dsDNA Oligonucleotide and Imidazolium Chloride Ionic Liquids: Effect of Alkyl Chain Length, Part I.

Ionic liquids (ILs) have become nearly ubiquitous solvents and their interactions with biomolecules has been a focus of study. Here, we used the fluorescence emission of DAPI, a groove binding fluorophore, coupled with molecular dynamics (MD) simulations to report on interactions between imidazolium chloride ([Imn,1]+) ionic liquids and a synthetic DNA oligonucleotide composed entirely of T/A bases (7(TA)) to elucidate the effects ILs on a model DNA duplex. Spectral shifts on the order of 500-1000 cm-1, spectral broadening (~1000 cm-1), and excitation and emission intensity ratio changes combine to give evidence of an increased DAPI environment heterogeneity on added IL. Fluorescence lifetimes for DAPI/IL solutions yielded two time constants 0.15 ns (~80% to 60% contribution) and 2.36-2.71 ns for IL up to 250 mM. With DNA, three time constants were required that varied with added IL (0.33-0.15 ns (1-58% contribution), ~1.7-1.0 ns (~5% contribution), and 3.8-3.6 ns (94-39% contribution)). MD radial distribution functions revealed that π-π stacking interactions between the imidazolium ring were dominant at lower IL concentration and that electrostatic and hydrophobic interactions become more prominent as IL concentration increased. Alkyl chain alignment with DNA and IL-IL interactions also varied with IL. Collectively, our data showed that, at low IL concentration, IL was primarily bound to the DNA minor groove and with increased IL concentration the phosphate regions and major groove binding sites were also important contributors to the complete set of IL-DNA duplex interactions.

Surface Interaction of Ionic Liquids: Stabilization of Polyethylene Terephthalate-Degrading Enzymes in Solution.

The effect of aqueous solutions of selected ionic liquids solutions on Ideonella sakaiensis PETase with bis(2-hydroxyethyl) terephthalate (BHET) substrate were studied by means of molecular dynamics simulations in order to identify the possible effect of ionic liquids on the structure and dynamics of enzymatic Polyethylene terephthalate (PET) hydrolysis. The use of specific ionic liquids can potentially enhance the enzymatic hydrolyses of PET where these ionic liquids are known to partially dissolve PET. The aqueous solution of cholinium phosphate were found to have the smallest effect of the structure of PETase, and its interaction with (BHET) as substrate was comparable to that with the pure water. Thus, the cholinium phosphate was identified as possible candidate as ionic liquid co-solvent to study the enzymatic hydrolyses of PET.

Potential Application of Ionic Liquids in Pharmaceutical Dosage Forms for Small Molecule Drug and Vaccine Delivery System.

Ionic liquids are salts in which the ions are poorly coordinated, which causes them to exist in liquid form below 100°C, or at room temperature. Therefore, these are also defined as room temperature ionic liquids (RTILs). In ionic liquids, at least one ion has a delocalized charge and one component is organic, which prevents the formation of a stable solid form of crystal lattice. Physical properties of ionic liquids, such as melting point, viscosity, and solubility of starting materials and other solvents, are impacted by the substituents on the organic component and by the counterions. Many ionic liquids have even been developed to address specific synthetic problems and that is the reason these are also termed as "designer solvents". Ionic liquids are considered as "green solvents" that exhibit several unique characteristics such as high ionic conductivity, high solvation power, thermal stability, low volatility, and recyclability. Although very useful with several advantages, ionic liquids have some limitations that include high cost and ease of recycling. Moreover, the toxicity and biodegradability of ionic liquids are not yet well understood. Nonetheless, ionic liquids can potentially be used in the field of pharmacy in drug design and formulation development. In drug or vaccine dosage formulation development, ionic liquids can be used as a solubility enhancer, permeability enhancer, stabilizer, targeted delivery inducer, stealth property provider or bioavailability enhancer. In this article we reviewed the physical properties of ionic liquids and potential application of ionic liquids in developing formulations for vaccines and small molecule drugs (A table has been added).

Functionalized composite nanofiber membranes for selective steroid hormone micropollutants uptake from water: Role of cyclodextrin type.

Cyclodextrins (CD) entrapped in nanofiber composite membranes are potential selective adsorbing materials to remove steroid hormone (SHs) micropollutants from water. This study aims to elucidate the role of CD macrocyclic host type on the SHs inclusion complexation and uptake in filtration. Three CD types (α, ß, and γ) are cross-linked with epichlorohydrin to form polymers (αCDP, ßCDP and γCDP) and entrapped into a nanofiber composite membrane by electrospinning. TGA analysis confirmed the CD entrapment into the nanofiber without loss of CD molecules during filtration. The CD type plays a dominant role in controlling the removal of different SHs. A similar removal (range 33 to 50 %) was observed with αCDP, irrespective of the SH type. In contrast, removal and uptake dependent on SH type were observed for ß and γCDP, with the highest removal of 74 % for progesterone, followed by estradiol (46 %) and estrone (27 %) and the lowest removal of 3 % for testosterone. Molecular dynamic (MD) simulation revealed a stronger and more stable complex formed with ßCDP, as demonstrated by: i) the closer spatial distribution of SH molecules from the ßCDP cavity and, ii) the quantum chemistry calculations of the lower de-solvation energy (+6.0 kcal/mol), which facilitates the release of water molecules from interacting interface of CD molecule and hormone. Regarding γCDP, the highest de-solvation energy (+8.3 kcal/mol) poses an energetic barrier, which hinders the formation of the inclusion complex. In the case of αCDP, a higher interaction energy (-8.9 kcal/mol) compared to ßCDP (-4.9 kcal/mol) was obtained, despite the broader spatial distribution observed from the MD simulation attributed to a dominant hydrogen bonding interaction with the OH primary groups on the external surface cavity. The findings highlight the relevance of the CD type in designing selective adsorbing membranes for steroid hormone micropollutant uptake. Experimental results and MD simulation suggest that ßCD is the most suitable CD type for steroid hormone uptake, due to a more stable and stronger inclusion complexation than α and γCD.

Local and cooperative structural transitions of double-stranded DNA in choline-based deep eutectic solvents.

The possibility of using deep eutectic solvents (DESs) as co-solvents for stabilizing and preserving the native structure of DNA provides an attractive opportunity in the field of DNA biotechnology. The rationale of this work is a systematic investigation of the effect of hydrated choline-based DES on the structural stability of a 30-base-pair double-stranded DNA model via a combination of spectroscopic experiments and MD simulations. UV absorption and CD experiments provide evidence of a significant contribution of DESs to the stabilization of the double-stranded canonical (B-form) DNA structure. Multi-wavelength synchrotron UV Resonance Raman (UVRR) measurements indicate that the hydration shell of adenine-thymine pairs is strongly perturbed in the presence of DESs and that the preferential interaction between H-bond sites of guanine residues and DESs is significantly involved in the stabilization of the dsDNA. Finally, MD calculations show that the minor groove of DNA is significantly selective for the choline part of the investigated DESs compared to the major groove. This finding is likely to have a significant impact not only in terms of thermal stability but also in the modulation of ligand-DNA interactions.

Adsorption of common greywater pollutants and nutrients by various biochars as potential amendments for nature-based systems: Laboratory tests and molecular dynamics.

Spruce wood and Typha (wetland plant) derived biochars pyrolyzed at 350 °C and 600 °C were tested for their sorption affinity for organic pollutants (diclofenac, methylparaben, benzotriazole and sodium 1-decanesulfonate) and nutrients (nitrate, ammonium, phosphate and boron) commonly found in greywater. Batch and column studies combined with molecular dynamics modelling determined the sorption capacity, kinetics, and described the underlying mechanisms. The spruce biochar (600 °C) exhibited the highest sorption capacity mainly for the tested organics. The dynamic test performed for spruce biochar (600 °C) showed that the magnitude of desorption was low, and the desorbed amount ranged between 3 and 11 %. Molecular dynamics modelling (a computational tool for elucidating molecular-level interactions) indicated that the increased sorption of nitrate and boron on spruce biochar (600 °C) could be attributed to hydrophobic interactions. The molecular dynamics shows that predominant adsorption of organic pollutants was governed by π-π stacking, with a minor role of hydrogen-bonding on the biochar surface. In summary, higher pyrolysis temperature biochar yielded greater adsorption capacity greywater borne contaminants and the reaction temperature (10-34 °C) and presence of anionic surfactant had a limited effect on the adsorption of organic pollutants, suggesting efficacious application of biochar in general for greywater treatment in nature-based systems.

Expansion of access tunnels and active-site cavities influence activity of haloalkane dehalogenases in organic cosolvents.

The use of enzymes for biocatalysis can be significantly enhanced by using organic cosolvents in the reaction mixtures. Selection of the cosolvent type and concentration range for an enzymatic reaction is challenging and requires extensive empirical testing. An understanding of protein-solvent interaction could provide a theoretical framework for rationalising the selection process. Here, the behaviour of three model enzymes (haloalkane dehalogenases) was investigated in the presence of three representative organic cosolvents (acetone, formamide, and isopropanol). Steady-state kinetics assays, molecular dynamics simulations, and time-resolved fluorescence spectroscopy were used to elucidate the molecular mechanisms of enzyme-solvent interactions. Cosolvent molecules entered the enzymes' access tunnels and active sites, enlarged their volumes with no change in overall protein structure, but surprisingly did not act as competitive inhibitors. At low concentrations, the cosolvents either enhanced catalysis by lowering K(0.5) and increasing k(cat), or caused enzyme inactivation by promoting substrate inhibition and decreasing k(cat). The induced activation and inhibition of the enzymes correlated with expansion of the active-site pockets and their occupancy by cosolvent molecules. The study demonstrates that quantitative analysis of the proportions of the access tunnels and active-sites occupied by organic solvent molecules provides the valuable information for rational selection of appropriate protein-solvent pair and effective cosolvent concentration.

A new proton conductive liquid with no ions: pseudo-protic ionic liquids.

Liquids with no ions! Raman analysis and quantum calculations suggest that electrically neutral molecular species predominantly exist in an N-methylimidazole and acetic acid equimolar mixture, and that ionic species are rather minor. Nevertheless, the mixture has significant ionic conductivity, and shows "good ionic" or "superionic" behavior (see figure). It may be suitable to call such liquids "pseudo-ionic liquids" rather than "ionic liquids".

Competitive formation of molecular inclusion complexes of chlordecone and ß-hexachlorocyclohexane with natural cyclodextrins: DFT and molecular dynamics study.

CONTEXT: Chlordecone (CLD) and ß-hexachlorocyclohexane (ß-HCH) are chlorinated pesticides that coexist as persistent organic pollutants in the groundwater of several countries in the Caribbean, being an environmental issue. This work evaluates theoretically the competitive formation of host-guest complexes pesticides@cyclodextrines (CDs) as an alternative for water purification and selective separation of pesticides. METHODS: Quantum mechanical calculations based on density functional theory (DFT) and classical molecular dynamics (MD) simulations were used to achieve information on geometries, energies, structure, and dynamics of guest-host complexes in the gas phase, implicit solvent medium, and in aqueous solutions. RESULTS: DFT studies showed that interactions of both pesticides with CDs are mediated by steric factors and guided by maximization of the hydrophobic interactions either with the other pesticide or with the CD cavity's inner atoms. MD results corroborate the formation of stable complexes of both pesticides with the studied CDs. α-CD exhibited a preference for the smaller ß-HCH molecule over the CLD that could not perturb the formed complex. CONCLUSIONS: The simulation of competitive formation with γ-CD illustrated that this molecule could accommodate both pesticides inside its cavity. These results suggest that CDs with smaller cavity sizes such as α-CD could be used for selective separation of ß-HCH from CLD in water bodies, while γ-CD could be used for methods that aim to remove both pesticides at the same time.

Hexahelicene DNA-binding: Minor groove selectivity, semi-intercalation and chiral recognition.

In this contribution, we focused on a fundamental study targeting the interaction of water-soluble [6]helicene derivative 1 (1-butyl-3-(2-methyl[6]helicenyl)-imidazolium bromide) with double-stranded (ds) DNA. A synthetic 30-base pair duplex, plasmid, chromosomal calf thymus and salmon DNA were investigated using electrochemistry, electrophoresis and spectroscopic tools supported by molecular dynamics (MD) and quantum mechanical approaches. Both experimental and theoretical work revealed the minor groove binding of 1 to the dsDNA. Both the positively charged imidazole ring and hydrophobic part of the side chain contributed to the accommodation of 1 into the dsDNA structure. Neither intercalation into the duplex DNA nor the stable binding of 1 to single-stranded DNA were found in topoisomerase relaxation experiments with structural components of 1, i.e. [6]helicene (2) and 1-butyl-3-methylimidazolium bromide (3), nor by theoretical calculations. Finally, the binding of optically pure enantiomers (P)-1 and (M)-1 was studied using circular dichroism spectroscopy, isothermal titration calorimetry and UV Resonance Raman (UVRR) methods. Using MD and quantum mechanical methods, minor groove and semi-intercalation were proposed for compound 1 as the predominant binding modes. From the UVRR findings, we also can conclude that 1 tends to preferentially interact with adenine and guanine residues in the structure of dsDNA.

The C-terminal basic residues contribute to the chemical- and voltage-dependent activation of TRPA1.

The ankyrin transient receptor potential channel TRPA1 is a non-selective cationic channel that is expressed by sensory neurons, where it can be activated by pungent chemicals, such as AITC (allyl isothiocyanate), cinnamon or allicin, by deep cooling (<18 °C) or highly depolarizing voltages (>+100 mV). From the cytoplasmic side, this channel can be regulated by negatively charged ligands such as phosphoinositides or inorganic polyphosphates, most likely through an interaction with as yet unidentified positively charged domain(s). In the present study, we mutated 27 basic residues along the C-terminal tail of TRPA1, trying to explore their role in AITC- and voltage-dependent gating. In the proximal part of the C-terminus, the function-affecting mutations were at Lys969, Arg975, Lys988 and Lys989. A second significant region was found in the predicted helix, centred around Lys1048 and Lys1052, in which single alanine mutations completely abolished AITC- and voltage-dependent activation. In the distal portion of the C-terminus, the charge neutralizations K1092A and R1099A reduced the AITC sensitivity, and, in the latter mutant, increased the voltage-induced steady-state responses. Taken together, our findings identify basic residues in the C-terminus that are strongly involved in TRPA1 voltage and chemical sensitivity, and some of them may represent possible interaction sites for negatively charged molecules that are generally considered to modulate TRPA1.

Metallic Effects on p-Hydroxyphenyl Porphyrin Thin-Film-Based Planar Optical Waveguide Gas Sensor: Experimental and Computational Studies.

Metal effects on the gas sensing behavior of metal complexes of 5,10,15,20-tetrakis(4-hydroxyphenyl)porphyrin (THPP) thin film was investigated in terms of detecting NO2 gas by the planar optical waveguide. For this purpose, several THPP and metal complexes were synthesized with different central metal ions: Co(II), Ni(II), Cu(II), and Zn(II). Planar optical gas sensors were fabricated with the metalloporphyrins deposited on K+ ion-exchanged soda-lime glass substrate with the spin coating method serving as host matrices for gas interaction. All of the THPP complex's films were fully characterized by UV-Vis, IR and XPS spectroscopy, and the laser light source wavelength was selected at 520 and 670 nm. The results of the planar optical waveguide sensor show that the Zn-THPP complex exhibits the strongest response with the lowest detectable gas concentration of NO2 gas for both 520 nm and 670 nm. The Ni-THPP and Co-THPP complexes display good efficiency in the detection of NO2, while, on the other hand, Cu-THPP shows a very low interaction with NO2 gas, with only 50 ppm and 200 ppm detectable gas concentration for 520 nm and 670 nm, respectively. In addition, molecular dynamic simulations and quantum mechanical calculations were performed, proving to be coherent with the experimental results.

Explaining the interaction of mangiferin with MMP-9 and NF-ƙß: a computational study.

Mangiferin is a glycosylated xanthone widely distributed in nature, which exhibits wide pharmacological activities, highlighting its anti-cancer properties. Mangiferin interferes with inflammation, lipid, and calcium signaling, which selectively inhibits multiple NFkB target genes as interleukin-6, tumor necrosis factor, plasminogen, and matrix metalloproteinase, among others. In this work, the interactions of this polyphenol with MMP-9 and NF-κß are characterized by using computational chemistry methods. The results show MMP-9 inhibition by mangiferina is characterized for the interact with the catalytic Zn atom through a penta-coordinate structure. It is also demonstrated through a strong charge transfer established between mangiferin and Zn in the QM/MM study. Concerning the mangiferin/NF-κß system, the 92.3% of interactions between p50 sub-unity and DNA are maintained with a binding energy of - 8.04 kcal/mol. These findings indicate that mangiferin blocks the p50-p65/DNA interaction resulting in the loss of the functions of this hetero-dimeric member and suggesting inhibition of the cancer progression. Experimental results concerning the anti-cancer properties of mangiferin show that this natural compound can inhibit selectively MMP-9 and NF-ƙß. Although the anti-tumor properties of mangiferin are well defined, its molecular mechanisms of actions are not described. In this work, a computational study is carried out to characterize the interactions of mangiferin with these molecular targets. The results obtained corroborate the anti-proliferative and anti-apoptotic activity of mangiferin and provide a depiction of its mechanisms of action.

Non-covalent modification of single wall carbon nanotubes (SWCNTs) by thienothiophene derivatives.

Non-covalent functionalization of single wall carbon nanotubes (SWCNTs) has been conducted using several binding agents with surface π-interaction forces in recent studies. Herein, we present the first example of non-covalent functionalization of sidewalls of SWCNTs using thienothiophene (TT) derivatives without requiring any binding agents. Synthesized TT derivatives, TT-CN-TPA, TT-CN-TPA2 and TT-COOH-TPA, were attached directly to SWCNTs through non-covalent interactions to obtain new TT-based SWCNT hybrids, HYBRID 1-3. Taking advantage of the presence of sulfur atoms in the structure of TT, HYBRID 1, as a representative, was treated with Au nanoparticles for the adsorption of Au by sulfur atoms, which generated clear TEM images of the particles. The images indicated the attachment of TTs to the surface of SWCNTs. Thus, the presence of sulfur atoms in TT units made the binding of TTs to SWCNTs observable via TEM analysis through adsorption of Au nanoparticles by the sulfur atoms. Surface interactions between TTs and SWCNTs of the new hybrids were also clarified by classical molecular dynamic simulations, a quantum mechanical study, and SEM, TEM, AFM and contact angle (CA) analyses. The minimum distance between a TT and a SWCNT reached up to 3.5 Å, identified with strong peaks on a radial distribution function (RDF), while maximum interaction energies were raised to -316.89 kcal mol-1, which were determined using density functional theory (DFT).

Modulation of global stability, ligand binding and catalytic properties of trypsin by anions.

Specific salts effect is well-known on stability and solubility of proteins, however, relatively limited knowledge is known regarding the effect on catalytic properties of enzymes. Here, we examined the effect of four sodium anions on thermal stability and catalytic properties of trypsin and binding of the fluorescent probe, p-aminobenzamidine (PAB), to the enzyme. We show that the specific anions effect on trypsin properties agrees with the localization of the anions in the Hofmeister series. Thermal stability of trypsin, Tm, the affinity of the fluorescent probe to the binding site, Kd, and the rate constant, kcat, of trypsin-catalyzed hydrolysis of the substrate N-benzoyl-L-arginine ethyl ester (BAEE) increase with increasing kosmotropic character of anions in the order: perchlorate

Specific anion effect on properties of HRV 3C protease.

Specific salts effect is intensively studied from the prospective of modification of different physico-chemical properties of biomacromolecules. Limited knowledge of the specific salts effect on enzymes led us to address the influence of five sodium anions: sulfate, phosphate, chloride, bromide, and perchlorate, on catalytic and conformational properties of human rhinovirus-14 (HRV) 3C protease. The enzyme conformation was monitored by circular dichroism spectrum (CD) and by tyrosines fluorescence. Stability and flexibility of the enzyme have been analyzed by CD in the far-UV region, differential scanning calorimetry and molecular dynamics simulations, respectively. We showed significant influence of the anions on the enzyme properties in accordance with the Hofmeister effect. The HRV 3C protease in the presence of kosmotropic anions, in contrast with chaotropic anions, exhibits increased stability, rigidity. Correlations of stabilization effect of anions on the enzyme with their charge density and the rate constant of the enzyme with the viscosity B-coefficients of anions suggest direct interaction of the anions with HRV 3C protease. The role of stabilization and decreased fluctuation of the polypeptide chain of HRV 3C protease on its activation in the presence of kosmotropic anions is discussed within the frame of the macromolecular rate theory.