Kinetic studies on the interaction of ferricytochrome c with anionic surfactants

The kinetics of absorbance and fluorescence changes of cytochrome c as indu ced by an aqueous solution of the anionic surfactant sodium dodecyl sulfate (SDS) or sodium bis(2-ethylhexyl)sulfosuccinate (AOT) are studied. The res ults are compared with far-UV circular dichroism (CD) spectra. Both surfact ants cause similar alterations in the secondary structure of cytochrome c, while their influence on the heme environment of cytochrome c is different. In the presence of AOT below and above critical micellar concentration a c onversion of the low-spin native cytochrome c to a denatured low-spin prote in not having methionine ligand takes place. In the presence of SDS micelle s conversion of the native protein to a denatured mixed-spin form occurs. T he changes in the heme group induced by both surfactants occur independentl y of the alterations in tertiary structure.