Abstract
Apparent molar volumes (Vf) and viscosities (h) for 0.00005 to 0.0004 kg.mol-1(50 to 400 mmol kg-1) aqueous methotrexate (MTX), gram (Gp) and soya bean (SBp) proteins, and similar compositions of Gp and SBp each in 50 to 400 mmol kg-1 aqueous MTX were determined at 298.15, 303.15 and 308.15K. The Vfvalues are positive except aqueous MTX and listed as SBp > Gp > MTX in aqueous and SBp > Gp in MTX solutions, respectively. It infers weaker hydrophobic heteromolecular interaction of SBp in binary and ternary systems. The higher h values of SBp and Gp in MTX than those of aqueous MTX prove strengthening of hydrophobic interactions of proteins by MTX. It illustrates the conformational changes of proteins; slightly higher Vf values of SBp than of Gp. The MTX confirm higher structural activity in biological process. The Vf0 of MTX increases with K and decrease with composition. But with compositions the values continuously decrease with lower magnitude. Key words: Density, Apparent molal volume, viscosity B coefficient, methotrexate, soya bean, gram protein.
Highlights
Thermodynamics and transport functions of naturally occurring proteins in aqueous solution are of biophysical significance
Due to dominance of spectroscopic techniques, only limited physico-chemical studies are available in literature; soya and gram proteins have never been focused for such studies
The ρ, Vφ and η data are least square fitted against m for values at infinite dilution referred to as limiting values) from the following equation: ρ = ρ0 + Sd m
Summary
Thermodynamics and transport functions of naturally occurring proteins in aqueous solution are of biophysical significance. Due to dominance of spectroscopic techniques, only limited physico-chemical studies are available in literature; soya and gram proteins have never been focused for such studies. Majority of proteins responds to aqueous and mixed solvent due to polyionic nature. Solvation has become an interesting tool for solute-solvent interactions, which gives some insights of structural interactions useful for biological activities due to conformational states. The physico-chemical characterizations of proteins in drug solutions have not been paid adequate attention and scarcity of such data with protein-drug solutions is noted.
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