A new strategy to induce gamma-turns: peptides composed of alternating alpha-aminoxy acids and alpha-amino acids.
It is known that the seven-membered-ring intramolecular hydrogen bond (gamma-turn) is seldom formed in naturally occurring peptides composed of alpha-amino acids. Here we report a new strategy to induce gamma-turns in short linear peptides. We designed and synthesized several peptides (1-5) containing alternating alpha-l-aminoxy acids and alpha-d-amino acids. 1H NMR studies revealed that the gamma-turn could be initiated by the following N-O turn, an eight-membered-ring intramolecular hydrogen bond induced by an alpha-aminoxy acid. Moreover, NOESY and CD studies suggested peptides 4 and 5 form a novel secondary structure, a mixed 7-8 helix. Theoretical calculations on several di-, tri-, and tetrapeptide models provided strong support to the above conclusions.
Yang
Dan
D
Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, China. yangdan@hku.hk
Li
Wei
W
Qu
Jin
J
Luo
Shi-Wei
SW
Wu
Yun-Dong
YD
D000577:Amides / Q000737:chemistry; D000596:Amino Acids / Q000737:chemistry*; D002942:Circular Dichroism; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D010455:Peptides / Q000737:chemistry*; D011487:Protein Conformation; D017433:Protein Structure, Secondary
D000577:Amides; D000596:Amino Acids; D010455:Peptides