3] Determination of protein molecular weight in complexes with detergent without knowledge of binding

Abstract

This chapter is concerned with the use of sedimentation equilibrium, a procedure that is generally applicable to proteins in the molecular weight range 10,000 to 500,000 and can be used conveniently for protein-amphiphile complexes without interference from non-protein-containing detergent micelles. This chapter presents a summary of the theoretical treatment of sedimentation equilibrium in a centrifugal field for systems containing two or more components and discusses the effects of specific interactions between the protein and solute molecules. It then proceeds to a description of experimental procedures and present examples of the application of this technique to protein-amphiphile complexes. Partial specific volumes are tabulated for amino acid residues, carbohydrates, and a number of detergents and lipids. Atomic and group partial molar volumes that are used to calculate partial specific volumes for chemical compounds are also provided. The chapter's consideration is the determination of protein molecular weight in a homogeneous system by a rigorous thermodynamic method.