Studies on the formation of bioconjugates of Endoglucanase with colloidal gold

We report herein the formation of Endoglucanase–colloidal gold bioconjugates under enzyme friendly conditions. The bioconjugates were formed by simple mixing of the enzyme molecules with colloidal gold at pH 5, centrifugation and subsequent redispersion in appropriate buffer solutions. The bioconjugates in solution were characterized by UV–vis, fluorescence spectroscopy and biocatalytic activity measurements. The films of the bioconjugate material obtained by solvent evaporation on suitable substrates were further analysed by transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy. TEM analysis showed the gold particles to be in a close-packed structure with well-defined separations indicating effective conjugation with the enzyme molecules. Fluorescence spectroscopy and biological activity measurements of the bioconjugate clearly showed the intactness of the tertiary structure of the enzyme. The bioconjugate material exhibited an increased half-life of the enzyme at 60 °C and pH 9 relative to that of the free enzyme in solution, thus highlighting the role of colloidal gold particles in stabilizing the enzyme molecules