Structural and energetic relations between ? turns

✍ Scribed by M�hle, Kerstin; Gu�mann, Martin; Hofmann, Hans-J�rg

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 275 KB
• Volume: 18
• Category: Article
• ISSN: 0192-8651
• DOI: 10.1002/(sici)1096-987x(199708)18:11<1415::aid-jcc8>3.0.co;2-o

✦ Synopsis

A systematic quantum chemical study on the structure and stability of the major types of ␤-turn structures in peptides and proteins was Ž performed at different levels of ab initio MO theory MP2r6-31G*, HFr6-31G*, . HFr3-21G considering model turns of the general type Ac-X -Y aa aa -NHCH with the amino acids glycine, L-and D-alanine, aminoisobutyric acid, 3

and L-proline. The influence of correlation effects, zero-point vibration energies, thermal energies, and entropies on the turn formation was examined. Solvent effects on the turn stabilities were estimated employing quantum chemical Ž continuum approaches Onsager's self-consistent reaction field and Tomasi's . polarizable continuum models . The results provide insight into the geometry and stability relations between the various ␤-turn subtypes. They show some characteristic deviations from the widely accepted standard rotation angles of ␤ turns. The stability order of the ␤-turn subtypes depends strongly on the amino acid type. Thus, the replacement of L-amino acids in the two conformationdetermining turn positions by D-or ␣,␣-disubstituted amino acid residues generally increases the turn formation tendency and can be used to favor distinct ␤-turn subtypes in peptide and protein design. The ␤-turn subtype preferences, depending on amino acid structure modifications, can be well illustrated by molecular dynamics simulations in the gas phase and in aqueous solution.