Refolding of urea denatured cytochrome c : Role of hydrophobic tail of the cationic gemini surfactants

Multivariable analysis of egg white protein-chitosan interaction: Influence of pH, temperature, biopolymers ratio, and ionic concentration

The influence of pH, temperature, biopolymer ratio, total concentration, and ionic concentration on the interaction between egg white protein (EWP) and chitosan (CS) was investigated through turbidity, zeta potential, and state diagram in our research. In addition, phase behavior was observed under various conditions. The turbidity of EWP remained low (turbidity < 0.03) and basically unchanged at a wide range of pH (4.0-8.0), while the turbidity of CS was slightly higher (turbidity < 0.2) after pH 7.0 than before. Moreover, under the same conditions, a sharply rising peak pattern was observed for the complex between EWP and CS. The maximum turbidity value was observed at 55 °C, and the temperature had a mild effect on turbidity. The optimum EWP to CS ratio was found to be 12:1 based on the turbidity curves and state diagrams influenced by different biopolymer mixing ratios. With the enhanced concentrations of total biopolymer, the maximum turbidity rose insignificantly above 0.1%.

Molecular Interaction of Amino Acid-Based Gemini Surfactant with Human Serum Albumin: Tensiometric, Spectroscopic, and Molecular Docking Study

Binding effect and interaction of N,N'-dialkyl cystine based gemini surfactant (GS); 2(C₁₂Cys) with human serum albumin (HSA) were systematically investigated by the techniques such as surface tension measurement, UV-visible spectroscopy, fluorescence spectroscopy, circular dichroism (CD) spectroscopy, and molecular docking studies. The surface tension measurement exhibited that HSA shifted the critical micelle concentration of the 2(C₁₂Cys) GS to the higher side that confirms the complex formation among 2(C₁₂Cys) GS and HSA which was also verified by UV-visible, fluorescence, and CD spectroscopy. Increase in the concentration of 2(C₁₂Cys) GS increases the absorption of the HSA protein but has a reverse effect on the fluorescence intensity. The analysis of UV-visible study with the help of a static quenching method showed that the value acquired for the bimolecular quenching constant (k _q) quenches the intrinsic fluorescence of the HSA protein. Synchronous fluorescence spectrometry declared that the induced-binding conformational changes in HSA and CD results explained the variations in the secondary arrangement of the protein in presence of 2(C₁₂Cys) GS. The present study revealed that the interaction between 2(C₁₂Cys) GS and HSA is important for the preparation and properties of medicines. Molecular docking study provides insight into the specific binding site of 2(C₁₂Cys) GS into the sites of HSA.

Synthesis of Novel Benzimidazolium Gemini Surfactants and Evaluation of Their Anti-Candida Activity

Owing to the rise in antimicrobial and chemotherapeutic drug resistance, there is a desperate need to formulate newer as well as more effective agents. With this perspective, here we outline the synthesis of two novel gemini surfactants with different substitutions at the nitrogen atom of the benzimidazolium ring. Both the compounds induced significant reductions in Candida growth in various yeast strains. The reduction in Candida growth seemed likely through the reduction in ergosterol biosynthesis: a sterol constituent of yeast cell membranes. Different concentrations of both compounds were used to determine the cellular ergosterol content which indicates an important disordering of the ergosterol biosynthetic pathway. Cytotoxic studies were carried out using HEK 293 (human embryonic-kidney cells) and Galleria mellonella larvae (an in vivo model of antimicrobial studies). Administration of both the compounds to G. mellonella larvae diseased by the yeast Candida albicans resulted in increased survival indicating their in vivo activity.

A Polar Liquid Zwitterion Does Not Critically Destroy Cytochrome c at High Concentration: An Initial Comparative Study with a Polar Ionic Liquid

A polar carboxylate-type zwitterion with a small volume of water can dissolve cytochrome c without significant disruption, compared with the case of a popular polar carboxylate-type ionic liquid, 1-ethyl-3-methylimidazolium acetate. A change in the Soret, Q, and 615nm bands was not observed in the 80 wt-% polar zwitterion solution, whereas a shift in the Soret band, diminishing Q band, and appearance of the 615nm band was found in the 80 wt-% polar ionic liquid solution. It suggests that concentrated polar ionic liquid solutions critically disrupt the structure of cytochrome c, and the polar zwitterion solution used in this study was better than a 1-ethyl-3-methylimidazolium acetate solution in a high concentration range.

Fluorescence Resonance Energy Transfer, Small-Angle Neutron Scattering, and Dynamic Light Scattering Study on Interactions of Gemini Surfactants Having Different Spacer Groups with Protein at Various Regions of Binding Isotherms

The binding interactions of three gemini surfactants having different spacer groups (12-4-12, 12-8-12, and 12-4(OH)-12) with a high concentration (150 μM) of bovine serum albumin (BSA) at various regions of binding isotherms have been studied by means of steady-state fluorescence and fluorescence anisotropy, time-correlated single-photon counting fluorescence of trans-2-[4-(dimethylamino)styryl]benzothiazole, small-angle neutron scattering (SANS), and dynamic light scattering (DLS) measurements. The fluorescence resonance energy transfer phenomenon between the twisted intramolecular charge transfer fluorescent molecule, trans-2-[4-(dimethylamino)styryl]benzothiazole as an acceptor, and tryptophan 213 (Trp-213) of BSA as a donor has been successfully used to probe the binding interactions of gemini surfactants with protein at all regions of binding isotherms. The increasing order of energy transfer efficiency at a higher concentration range of surfactants is 12-8-12 > 12-4-12 > 12-4(OH)-12. Stronger binding of micelles of gemini surfactant molecules having a comparatively more hydrophobic spacer group with the hydrophobic segments of the protein results in closer approach of trans-2-[4-(dimethylamino)styryl]benzothiazole molecules solubilized in micelles to Trp-213. The average excited-state lifetimes become shorter with a trend of increase in contribution from the fast component and decrease in contribution from the slow component to the decay with increasing concentration of a surfactant. The nonradiative rate constant of trans-2-[4-(dimethylamino)styryl]benzothiazole increases with increasing concentration of a surfactant because the average microenvironment around it in protein-surfactant aggregates is more polar as compared to that in native protein. SANS and DLS measurements were carried out for the study of the structural deformations in the protein, on enhancement of the concentration of the gemini surfactants. The necklace and bead model has been used for the analysis of SANS data for the protein-surfactant complexes. At a higher concentration range, 12-8-12 and 12-4-12 have a slightly smaller fractal dimension and a larger correlation length as compared to 12-4(OH)-12. DLS data show that the increasing order of hydrodynamic diameter for the complexes of protein with three gemini surfactants in their high concentration range is 12-4(OH)-12 < 12-4-12 < 12-8-12.

Dynamics of Ionic Liquid-Assisted Refolding of Denatured Cytochrome c: A Study of Preferential Interactions toward Renaturation

In vitro refolding of denatured protein and the influence of the alkyl chain on the refolding of a protein were tested using long chain imidazolium chloride salts, 1-methyl-3-octylimidazolium chloride [C₈mim][Cl], and 1-decyl-3-methylimidazolium chloride [C₁₀mim][Cl]. The horse heart cytochrome c (h-cyt c) was denatured by urea and guanidinium hydrochloride (GdnHCl), as well as by base-induced denaturation at pH 13, to provide a broad overview of the overall refolding behavior. The variation in the alkyl chain of the ionic liquids (ILs) showed a profound effect on the refolding of denatured h-cyt c. The ligand-induced refolding was correlated to understand the mechanism of the conformational stability of proteins in aqueous solutions of ILs. The results showed that the long chain ILs having the [C₈mim]⁺ and [C₁₀mim]⁺ cations promote the refolding of alkali-denatured h-cyt c. The IL having the [C₁₀mim]⁺ cation efficiently refolded the alkali-denatured h-cyt c with the formation of the MG state, whereas the IL having the [C₈mim]⁺ cation, which is known to be compatible for protein stability, shows slight refolding and forms a different transition state. The lifetime results show successful refolding of alkaline-denatured h-cyt c by both of the ILs, however, more refolding was observed in the case of [C₁₀mim][Cl], and this was correlated with the fast and medium lifetimes (τ₁ and τ₂) obtained, which show an increase accompanied by an increase in secondary structure. The hydrophobic interactions plays an important role in the refolding of chemically and alkali-denatured h-cyt c by long chain imidazolium ILs. The formation of the MG state by [C₁₀mim][Cl] was also confirmed, as some regular structure exists far below the CMC of IL. The overall results suggested that the [C₁₀mim]⁺ cation bound to the unfolded h-cyt c triggers its refolding by electrostatic and hydrophobic interactions that stabilize the MG state.

Rational Design and Synthesis of Carboxylate Gemini Surfactants with an Excellent Aggregate Behavior for Nano-La2O3 Morphology-Controllable Preparation

A series of carboxylate gemini surfactants (CGS, C_n-Φ-C_n, n = 12, 14, 16, 18) with diphenyl ketone as a spacer group were prepared using a simple and feasible synthetic method. These CGS exhibited an excellent surface activity with extremely low critical micelle concentration (CMC) value (approximately 10^-5 mol/L), good performance in reducing surface tension (nearly 30 mN/m), and the ability of molecular self-assembly into different aggregate morphologies via adjusting the concentrations, which is attributed to the introduction of diphenyl ketone and carboxylic acid ammonium salt in the molecular structure. Moreover, the surface activity and self-assembly ability of CGS were further optimized by tuning the length of the tail chain. These excellent properties imply that CGS can be a soft template to prepare nanomaterials, especially in morphology-controllable synthesis. By adjusting the concentration of one of CGS (C₁₂-Φ-C₁₂), nano-La₂O₃ particles with diverse morphologies were obtained, including spherical shape, bead-chain shape, rod shape, velvet-antler shape, cedar shape, and bowknot shape. This work offers a vital insight into the rational design of template agents for the development of morphology-controllable nanomaterials.

Comparative effect of cationic gemini surfactant and its monomeric counterpart on the conformational stability and activity of lysozyme

Protein interactions with surfactants are dependent on their physiochemical properties.

Comparative effect of cationic gemini surfactant and its monomeric counterpart on the conformational stability and activity of lysozyme

Protein interactions with surfactants are dependent on their physiochemical properties.

Comparative effect of cationic gemini surfactant and its monomeric counterpart on the conformational stability and activity of lysozyme

Protein interactions with surfactants are dependent on their physiochemical properties.

Comparative effect of cationic gemini surfactant and its monomeric counterpart on the conformational stability and activity of lysozyme

Protein interactions with surfactants are dependent on their physiochemical properties.

Comparative effect of cationic gemini surfactant and its monomeric counterpart on the conformational stability and activity of lysozyme

Protein interactions with surfactants are dependent on their physiochemical properties.