INTERACTIONS BETWEEN BOVINE PLASMA ALBUMIN AND SODIUM DODECYL-SULFATE STUDIED BY MEANS OF C-13-NMR SPECTRA

The interactions between the protein, bovine plasma albumin, and surfactant, sodium dodecyl sulfate, have been studied by 13C‐nmr spectroscopy at pH 5.4–6.8 in D2O solution. The 13C chemical shifts and the 13C spin‐lattice relaxation time of the individual carbons of the surfactant were measured as a function of the molar ratio of the surfactant to albumin in order to analyze the surfactant‐protein interaction and the molecular motion of the surfactant. It was found that in the region of initial binding of the surfactant to the high‐affinity sites on the protein, both the surfactant head group and alkyl chain interact with the protein. With an excess of high‐affinity sites at the beginning of the reaction, surfactant molecules are in a micellelike environment in which the surfactant's alkyl chains are associated with nonpolar groups of the protein. Even after the denaturation by many surfactant bindings, much of the secondary and higher structure seems to remain intact. Copyright © 1979 John Wiley & Sons, Inc.