Protein Chemistry - Part 1 - General Protein Chemistry - Ashmarin I. P. 1968

Primary structure of the protein molecule

Essential and characteristic components of Proteins are Polypeptides, which typically consist of many dozens or even hundreds of Amino Acids. The fact that the polypeptide chain in proteins is a chain of main valences has been proven by the entire history of Protein Chemistry. Schematically, any polypeptide chain can be represented by the following general formula:

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where R represents the side chains (radicals) of the amino acids.

The unique Properties of Proteins are determined not only by the quantitative ratios among various amino acids, but also by their specific sequence within The polypeptide chains. The Amino Acid Composition of a protein and The sequence of amino acids in its polypeptide chains are referred to as the Introduction/19.html">Primary Structure of the protein. In addition to peptide bonds, the primary structure contains a certain number of disulfide bridges. Investigating the primary structure involves: 1) determining the number of polypeptide chains and establishing whether they are open or cyclic, 2) establishing the linear sequence (order of arrangement) of amino acids within the individual polypeptide chain or chains, and 3) determining the number and Location OF THE cross-linking disulfide bridges that bind these chains together within the protein molecule. Obviously, accomplishing this task requires, first and foremost, purified, homogenous protein preparations, since even a minor trace of foreign proteins can significantly skew the obtained results. Furthermore, researchers must have at their disposal a comprehensive suite of modern preparative and Analytical Methods, the combination of which enables the Determination of the primary structure of a protein molecule. Below, we will examine these methods and analytical techniques in greater detail.