The presence of multiple α,α-dialkyl amino acids such as α-methylalanine (α-aminoisobutyric acid, Aib) leads to predominantly helical structures, either with α-helical or 310-helical hydrogen bonding patterns. The crystal structure of emerimicin-(1-9) benzyl ester (Ac-Phe-Aib-Aib-Aib-Val-Gly-Leu-Aib-Aib-OBzl) reported here shows essentially pure α-helical character, whereas other similar compounds show predominantly 310-helical structures. The factors that govern helical preference include the inherent relative stability of the α-helix compared with the 310-helix, the extra hydrogen bond seen with 310-helices, and the enhanced electrostatic dipolar interaction of the 310-helix when packed in a crystalline lattice. The balance of these forces, when combined with the steric requirements of the amino acid side chains, determines the relative stability of the two helical conformations under a given set of experimental conditions.
|Number of pages||5|
|Journal||Proceedings of the National Academy of Sciences of the United States of America|
|State||Published - Feb 2 1990|
- [α-helix/α-aminoisobutyric acid (α-methylalanine)
- x-ray crystallography]