Effect of the environment and role of the pi-pi stacking interactions in the stabilization of the 3(10)-helix conformation in dehydroalanine oligopeptides.
{"title":"Effect of the environment and role of the pi-pi stacking interactions in the stabilization of the 3(10)-helix conformation in dehydroalanine oligopeptides.","authors":"C Alemän","doi":"","DOIUrl":null,"url":null,"abstract":"<p><p>A quantum-mechanical study of the chain-length dependent stability of the extended, 2(7)-ribbon and 3(10)-helix conformations in dehydroalanine (delta Ala) oligopeptides has been performed. To address the study, the oligopeptides delta Ala(n), where n varies from 1 to 6, were computed by using the semiempirical AMI methodology. Cooperative free-energy effects permit one to predict the stabilization of the 3(10)-helix with respect to the extended and 2(7)-ribbon conformations when the number of residues in the polypeptide chain increases. The interactions associated with the pi-electron density of the side chains can easily explain this finding. The effects of the solvent and the crystalline packing on the different conformations were modeled using a self-consistent reaction field (SCRF) method and a molecular mechanics approach to the packing, respectively. Both the aqueous and crystal environments seem to be a key factor in the stabilization of the helical conformation. Finally, the variations of electrostatic parameters such as atomic point charges and dipole moments in delta Ala-containing peptides with internal (conformation) and external (solvent) effects are discussed.</p>","PeriodicalId":14204,"journal":{"name":"International journal of peptide and protein research","volume":"46 5","pages":"408-18"},"PeriodicalIF":0.0000,"publicationDate":"1995-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"International journal of peptide and protein research","FirstCategoryId":"1085","ListUrlMain":"","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
引用次数: 0
Abstract
A quantum-mechanical study of the chain-length dependent stability of the extended, 2(7)-ribbon and 3(10)-helix conformations in dehydroalanine (delta Ala) oligopeptides has been performed. To address the study, the oligopeptides delta Ala(n), where n varies from 1 to 6, were computed by using the semiempirical AMI methodology. Cooperative free-energy effects permit one to predict the stabilization of the 3(10)-helix with respect to the extended and 2(7)-ribbon conformations when the number of residues in the polypeptide chain increases. The interactions associated with the pi-electron density of the side chains can easily explain this finding. The effects of the solvent and the crystalline packing on the different conformations were modeled using a self-consistent reaction field (SCRF) method and a molecular mechanics approach to the packing, respectively. Both the aqueous and crystal environments seem to be a key factor in the stabilization of the helical conformation. Finally, the variations of electrostatic parameters such as atomic point charges and dipole moments in delta Ala-containing peptides with internal (conformation) and external (solvent) effects are discussed.