Studies on the Interaction of SDS with Gelatin in Presence of Urea Derivatives

Abstract

The interactions of an anionic surfactant sodium dodecyl sulfate (SDS) in presence of urea and its derivatives with different percentage compositions of gelatin solutions were investigated by viscosity, conductivity, Fourier transform infrared spectroscopy (FTIR) and circular dichroism (CD) spectroscopic measurements at 35°C. The additives used were urea (U), thiourea (TU), mono methyl urea (MU), dimethyl urea (DMU), and tetra methyl urea (TMU). Circular dichroism spectroscopy reveals the linear decrease in molar ellipticity as the concentration of urea (and its derivatives) increases, without any change in the conformation of gelatin. This is contrary to the expected denaturation of gelatin in presence of urea. FTIR studies probe the characteristic effect of additive, thiourea on the gelatin-SDS system. The transition of gelatin from an unfolded state to the folded one has some resemblance to micelle formation because both processes are governed by the same basic intermolecular and ionic forces. In this work, we present an evidence for the stabilizing effect of urea and its alkyl derivatives in moderate concentration ranges of surfactant and gelatin.