Size and Structure of Cytochrome-c bound to Gold nano-clusters: Effect of Ethanol

Size and structure of cytochrome c (Cyt C) bound to gold nano-clusters (AuNC) were studied using fluorescence correlation spectroscopy (FCS) and circular dichroism (CD) spectroscopy. The CD spectra of Cyt C indicate that the ellipticity is almost completely lost on binding to AuNC which indicates unfolding. Addition of ethanol causes partial restoration of ellipticity and hence, structure of Cyt C. FCS data indicate that size (hydrodynamic radius, r H ) of free Cyt C is 17 Å which increases to 24 Å on binding to AuNC. This too suggests unfolding of Cyt C upon binding to AuNCs. Both the size and conformational relaxation time of Cyt C bound to AuNC vary non-monotonically with increase in ethanol content. Graphical Abstract Size, conformation dynamics and structure of cytochrome c (Cyt C) bound to gold nanoclusters (AuNC) have been studied using fluorescence correlation spectroscopy (FCS) and circular dichroism (CD). The CD spectra of Cyt C indicate that the helical structure is almost completely lost on binding to AuNC signifying unfolding. Addition of ethanol causes partial restoration of structure of Cyt C. FCS data indicate that both the size and conformational relaxation time of Cyt C bound to AuNC vary non-monotonically with increase in ethanol content.