Molecular interactions of cyclic alanylalanine and glycine betaine in aqueous metal chloride solutions

Abstract

The research thesis entitled ‘Molecular interactions of cyclic alanylalanine and glycine betaine in aqueous metal chloride solutions’ deals with the volumetric, compressibility and refractometric studies of two important biomolecules namely cyclic alanylalanine and glycine betaine in water as well as in aqueous solutions of NaCl, KCl, CaCl2, MgCl2, MnCl2, CoCl2, NiCl2 and ZnCl2 under varied conditions of concentration and temperature. The derived thermodynamic parameters have been computed from the experimental density, speed of sound and refractive index measurements. Hydrophobic hydration was observed in cyclic alanylalanine-metal chloride solutions through the results of volumetric and compressibility studies. While in glycine betaine-metal salts systems, a characteristic zwitterionic behaviour of glycine betaine molecule was elucidated. Effect of the size of the metal ions on the partial molar quantities in solutions of NaCl, KCl, CaCl2 and MgCl2 in biomolecules was investigated and the same has been attributed to the relative sizes of metal ions in solutions. However, transition metal-biomolecules systems, influence of metal to water bond distance in aqueous solutions on the solution behaviour has been observed. Hepler’s coefficients calculated for glycine betaine-transition metal salt solutions with varying concentrations reveal that glycine betaine behaves as a structure maker in these systems. However, in concentrated salt solutions it has been found that glycine betaine behaves as a structure breaker. The volumetric and compressibility studies have also been checked by the refractometric observations. The results of the present work may be used to elucidate the thermodynamic parameters of protein molecules under various environments.