Peptide Mapping and Amino Acid Analysis

Abstract

As we have seen in Chapter 1, what uniquely defines a specific protein is its amino acid sequence, or primary structure. The methodology for determining the sequential arrangement of amino acids in a protein or peptide has been in place for some time. The first protein for which a full amino acid sequence was determined was the peptide hormone insulin by Frederick Sanger in 1953. At the time, this work was considered a major breakthrough, since it proved that proteins have uniquely defined structures. Sanger received the Nobel Prize for this work in 1958. While much of the chemistry involved in amino acid sequencing is now automated, the determination of protein sequences remains a tedious and technically demanding effort that is best left to laboratories that specialize in these methods. Nevertheless, the generalist can gain insight into the structure of target proteins by a number of methods that provide indirect information of amino acid composition and arrangement. Peptide mapping and amino acid analysis are often combined to provide this type of information. In this chapter we shall describe the methods commonly employed for peptide mapping and amino acid analysis of proteins. As we shall see, these methods are readily accessible to most protein scientists. At the end of the chapter, we shall briefly discuss the basis for protein sequence analysis. Again, the actual determination of protein sequences is largely the realm of experts, but it is worthwhile reviewing the chemistry involved in sequence analysis, since this is such an important part of modern protein science.