Effect of different additives on the phase separation behavior and thermodynamics of p - tert -alkylphenoxy poly (oxyethylene) ether in absence and presence of drug

Physico-chemical parameters of phase separation of the mixture of BSA and triton X 100 in aqueous solutions of monohydroxy compounds

Clouding behavior and thermodynamic properties for the TX 100 + BSA mixture were investigated in aqueous and aq. alcoholic media. In an aqueous environment, the values of cloud point (CP), at which a clear solution becomes cloudy, for TX 100 decreases with augmentation of the concentration of BSA. The reverse result was obtained in the aq. alcoholic media. In this study, we have used ethanol (EtOH), 1-propanol (1-PrOH), and 2-butanol (2-BuOH) as alcohols. The changes of CP values in alcoholic media have been obtained in the following order: CP_H2O+EtOH > CP_H2O+2-BuOH > CP_H2O+1-PrOH. The standard free energy (∆G_c^o), standard enthalpy (∆H_c^o), and standard entropy (∆S_c^o) changes of clouding were derived at CP. The ΔG_c⁰ values of TX 100 + BSA decreases in the aqueous and alcoholic media with increasing the concentration of BSA and alcohol. This process becomes endothermic in the aq. alcoholic media. Different thermodynamic properties of transfer and entropy-enthalpy compensation parameters for the phase partitioning of the TX 100 + BSA mixture have been calculated and assessed properly.

Impact of salts on the phase separation and thermodynamic properties of mixed nonionic surfactants in absence/attendance of polyvinyl alcohol

Mixed surfactant systems are used in different applied fields like pharmaceutical formulation rather than single surfactant. Therefore, the determination of the clouding nature of the triton X-100 (TX-100) + Tween 80 (TW-80) mixture was carried out in H2O and polyvinyl alcohol (PVA). In the occurrence of PVA, the cloud point (CP) values of TX-100 initially enhance with enhancing the concentration of PVA and tend to decrease after a certain concentration. For different ratios of TX-100 and TW-80 mixture having the same concentration of both solutions, CP values increase through the decreasing ratios of TX-100 with/without PVA. In the presence of polymer, at higher ratios of TX-100 than TW-80, the CP values are higher in magnitudes in comparison to the aqueous medium but at lower ratios of TX-100, the value of CP are lower in magnitudes in comparison to the aqueous system. The CP values of the TX-100 + TW-80 mixture in the salt system are lower in magnitudes than the aqueous medium in both the absence/presence of PVA. However, a reduction of CP values was obtained to a large extent for Na2SO4 over NaCl in the case of lower volume ratios of TX-100. Various thermodynamic variables (standard free energy ( Δ G c o ${\Delta}{G}_{c}^{o}$ ), standard enthalpy ( Δ H c o ${\Delta}{H}_{c}^{o}$ ), standard entropy ( Δ S c o ${\Delta}{S}_{c}^{o}$ ) change, thermodynamic parameters of transfer (free energy of transfer ( Δ G c , t o ${\Delta}{G}_{c,t}^{o}$ ), and transfer of enthalpies ( Δ H c , t o ${\Delta}{H}_{c,t}^{o}$ )) of phase transition) were also determined.

Aggregation behavior of cetyldimethylethylammonium bromide under the influence of bovine serum albumin in aqueous/electrolyte solutions at various temperatures and compositions: conductivity and molecular dynamics study

Herein, we have investigated the interaction of bovine serum albumin (BSA), the most abundant globular protein, with a conventional cationic surfactant, cetyldimethylethylammonium bromide (CDMEAB), through a conductivity technique in the absence/presence of electrolyte solutions at various temperatures (298.15-323.15 K). The interaction of the protein with drugs/surfactants and other additives plays a crucial role in the body. Hence, the main concern of the study is to extract the impact of BSA on surfactant molecules and vice versa. From the specific conductivity versus concentration of surfactant plots, three different noticeable critical micelle concentration (c*) values were obtained for pure CDMEAB and its mixture with protein/protein + salts. The presence of BSA and electrolytes altered the c* values of CDMEAB revealing interactions among the studied constituents where the salt solutions reduced the c* values and created a convenient environment for favorable micellization. The negative magnitudes achieved for standard free energy changes (ΔG 0 m) suggest spontaneity of micellization while the values of ΔH 0 m and ΔS 0 m signified the existence of some electrostatic and hydrophobic interactions. The values of molar heat capacity (ΔC 0 m) were positive as well as small which was an indication of less structural deformation. Molecular Dynamics (MD) simulation for all atoms revealed that the salt ions promoted non-covalent interaction between BSA and CDMEAB, and such interactions were not observed in the absence of the salt. Protein structure remained nearly same in spite of strong interaction with CDMEAB as evident from the overall RMSD (root-mean-square deviation) values of the alpha carbons and backbone of the protein and RMSF (root-mean-square fluctuation) values of the amino acid residues present in BSA. In this work thermodynamic parameters of transfer (such as ΔG 0 m.tr., ΔH 0 m.tr., and ΔC 0 p.m.tr.) were also evaluated and the results are discussed in detail. Besides, contributions of enthalpy and entropy to free energy changes were also analyzed.