ABSTRACT
Integral membrane proteins possess extensive hydrophobic surfaces which allow them to function within or attached to a lipid bilayer. Their amphipathic nature has made them difficult to characterize biochemically and to crystallize for high resolution X-ray analysis. This chapter addresses the question of how to choose suitable detergents for membrane crystallization but mainly from the viewpoint of obtaining pure, homogeneous, and active protein preparations. It discusses the crystallization behavior of OmpF porin displays characteristics that are suggestive of a dominant role of the detergent in crystal nucleation and growth. A basic understanding of detergent chemistry is necessary when attempting any crystallization experiments on membrane proteins. The species we want to crystallize is a protein-detergent complex (PDC) which is soluble in aqueous solution by virtue of the bound detergent. Purity, as measured by the homogeneity and monodispersity of the PDC, is critical for the crystallization of membrane proteins.
