Abstract

Apparent molar volumes (V_f) 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 V_fvalues 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 V_f values of SBp than of Gp. The MTX confirm higher structural activity in biological process. The V_f⁰ 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.