(S) -C alpha-ethyl, C alpha-benzylglycine [ (S) - (alpha Et) Phe] peptides fold in left-handed helical structures
Doi, M.; Ishida, T.; Polese, A.; Formaggio, F.; Crisma, M.; Toniolo, C.; Broxterman, Q.B.; Kamphuis, J.
Peptide Research 8(5): 294-297
1995
ISSN/ISBN: 1040-5704 PMID: 8589552 Document Number: 453467
The first x-ray diffraction structure analysis of a C alpha-ethyl, C alpha-benzylglycine [(alpha Et)Phe]-containing peptide, N alpha-benzyloxycarbonyl-alpha-aminoisobutyryl-alpha-amino-isobutyr yl-(S)- C alpha-benzylglycyl-alpha-aminoisobutyric acid (methanol solvate), has been performed. In the crystal state the N alpha-protected tetrapeptide is folded in an incipient, left-handed 3(10)-helical structure. This finding confirms that the relationship between (alpha Et)Phe alpha-carbon chirality and screw sense of the helix that is formed is opposite to that exhibited by protein amino acids, including Phe.