The Proteins: Second Edition, Volume III

The early idea of protein as an amorphous, ill-defined substance has given way to the concept that proteins exist as specific and definable molecular substances. Using this concept it has been possible to treat the study of proteins as a true branch of chemistry, and this is the basis for much of the recent progress in understanding these important compounds. It will be the purpose of this chapter to review the ways in which proteins can be isolated and characterized as separate molecular species. We shall discuss the properties which permit separation and the detection of heterogeneity, review the available methods and their limitations, attempt to outline some particularly valuable general procedures, and speculate about new directions that research in the field of protein fractionation could take.