Peptides glycine-containing polypeptides

In addition to the glycine-containing polypeptides and peptides, we show here new results on the 170 NMR chemical shift and quadrupolar coupling constant of poly(L-alanine)s in both a-helix and P-sheet forms, in the solid state. There results help clarify the relationship between hydrogen-bond length and e2qQ/h and chemical shift parameters. 

The primary structure of a polypeptide is its sequence of amino acids. It is customary to write primary structures of polypeptides using the three-letter abbreviation for each amino acid. By convention, the structure is written so that the amino acid on the left bears the terminal amino group of the polypeptide and the amino acid on the right bears the terminal carboxyl group. Figure 13-35 shows the two dipeptides that can be made from glycine and serine. Although they contain the same amino acids, they are different molecules whose chemical and physical properties differ. Example shows how to draw the primary stmcture of a peptide. 

Calcium in this case would coordinate with acyl oxygens from the polypeptide backbone of the protein, because of its unique amino acid sequences and potential conformations348). Non-polar peptides have been isolated from elastin which consists almost entirely of the three non-polar amino acids glycine, valine, and proline349). Portions of porcine tropoelastin have been partially sequenced350). Repeating tetra-, penta-, and hexapeptides have been observed. The tetrapeptide contains the sequence —Gly—Gly—L—Val—L—Pro— the pentapeptide —L—Val—L—Pro-... 

Small peptides consist of a few amino acids. An example is Ala-Met-Gly, a peptide consisting of alanine, methionine, and glycine. The simplest peptide is called a dipeptide, and it contains a single peptide bond formed between the C atom of the carboxyl group of one amino acid and the N atom of the amino group of the second. In a polypeptide consisting of, for instance, 58 amino acids, there are 56 peptide bonds. The Ca-CO-N-Ca-CO-N-Ca-CO-N atoms of a peptide chain, without the R groups, is called the backbone. ... 

Kuroki, S., Takahashi, A., Ando, I., Shoji, A., and Ozaki, T., Hydrogen-bonding structural study of solid peptides and polypeptides containing a glycine residue by NMR spectroscopy, J. Mol. Struct. 323, 197-208 (1995). 

In this connection, Sperling and Elad (66) observed a mmetric induction in the photo-alkylation by ultra-violet li t of glycine residue in peptide containing cine and optically active amino acid residues (Table 12). In this case as well, the secondary conformation of polypeptide appears to exhibit a remarkable influence, as shown... 

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