Determining the Primary Structure of a Protein

Step 1 in determining the primary structure of a protein is to establish which amino acids are present and in what proportions. Breaking a protein down to its component amino acids is relatively easy heat a solution of the protein in 

Cleave protein at specific sites other than those in sample 3 

Combine information from overlapping peptides to get complete sequence 

The amino acid can be determined by four different analyses performed on four separate samples of the same protein. 

In Step 2, the identities of the N-terminal and G-terminal amino acids in a protein sequence are determined. This procedure is becoming less and less necessary as the sequencing of individual peptides improves, but it can be used to check whether a protein consists of one or two polypeptide chains. 

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To determine the primary structure of a protein that may contain a hundred or more amino acid units, it is necessary to... 

The analytical techniques frequently employed to determine the primary structure of a protein are listed in Table I. In general, most or all of these tests will be used for proof of structure, with a subset or streamlined versions of these techniques used to confirm identity on a lot-to-lot basis. 

The last step in determining the primary structure of a protein is to figure out the location of any disulfide bonds. This is done by hydrolyzing a sample of the protein that has intact disulfide bonds. From a determination of the amino acids in the cysteine-containing fragments, the locations of the disulfide bonds in the protein can be established (Problem 47). 

The sequence of amino acids determines the primary structure of a protein. Changing just a single amino acid in a critical position of the protein can significantly alter its activity and function and be the cause of disease and disorders. The amino acids are connected to each other in a head-to-tail fashion by formation of a peptide bond (Fig. 1.11), the condensation of a carboxylic and an amino group with the elimination of water. 

Proteins are polypeptides (i.e., polymers formed from amino acids). About 20 different amino acids appear in proteins. The sequence of amino acids determines the primary structure of a protein. The peptide link between the adjacent amino acids in other words, the group... 

There are 20 amino acids that are the building blocks of proteins (Fig. 6.1). Amino acids are j oined by peptide bonds in a precise order, which determines the primary structure of a protein. 

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