The interfacial behavior of cytochrome c studied by pendant-drop technique

Abstract

The adsorption properties of cytochrome c (cyt c) were characterized by surface tension measurements using the pendant-drop method employing the digital image analysis of the drop shape. The method was applied to the study of the protein conformation change due to acidification at low ionic strength. The observation of the saturated steady-state surface tension shows that decrease in pH induces its cooperative change centered around pH 2.5. This value is equal to the value of apparent pK of the acid-induced transition of the horse ferricyt c from a native state to the unfolded conformation. This indicates that the saturated steady-state surface tension is sensitive to the conformation of cyt c in bulk phase, and the pendant-drop method might be used to monitor changes in the tertiary structure of proteins.