title: Beta-hairpin formation in aqueous solution and in the presence of trifluoroethanol: a (1)H and (13)C nuclear magnetic resonance conformational study of designed peptides.
abstract: In order to check our current knowledge on the principles involved in beta-hairpin formation, we have modified the sequence of a 3:5 beta-hairpin forming peptide with two different purposes, first to increase the stability of the formed 3:5 beta-hairpin, and second to convert the 3:5 beta-hairpin into a 2:2 beta-hairpin. The conformational behavior of the designed peptides was investigated in aqueous solution and in 30% trifluoroethanol (TFE) by analysis of the following nuclear magnetic resonance (NMR) parameters: nuclear Overhauser effect (NOE) data, and C(alpha)H, (13)C(alpha), and (13)C(beta) conformational shifts. From the differences in the ability to adopt beta-hairpin structures in these peptides, we have arrived to the following conclusions: (i) beta-Hairpin population increases with the statistical propensity of residues to occupy each turn position. (ii) The loop length, and in turn, the beta-hairpin type, can be modified as a function of the type of turn favored by the loop sequence. These two conclusions reinforce previous results about the importance of beta-turn sequence in beta-hairpin folding. (iii) Side-chain packing on each face of the beta-sheet may play a major role in beta-hairpin stability; hence simplified analysis in terms of isolated pair interactions and intrinsic beta-sheet propensities is insufficient. (iv) Contributions to beta-hairpin stability of turn and strand sequences are not completely independent. (v) The burial of hydrophobic surface upon beta-hairpin formation that, in turn, depends on side-chain packing also contributes to beta-hairpin stability. (vi) As previously observed, TFE stabilizes beta-hairpin structures, but the extent of the contribution of different factors to beta-hairpin formation is sometimes different in aqueous solution and in 30% TFE.
authors.affiliation: Instituto de Química-Física Rocasolano, Consejo Superior de Investigaciones Científicas, Serrano 119, 28006-Madrid, Spain.
authors.forename: Clara M
authors.initials: CM
authors.lastname: Santiveri
authors.forename: David
authors.initials: D
authors.lastname: Pantoja-Uceda
authors.forename: Manuel
authors.initials: M
authors.lastname: Rico
authors.forename: M Angeles
authors.initials: MA
authors.lastname: Jiménez
mesh_terms: D000595:Amino Acid Sequence; D002247:Carbon Isotopes; D002851:Chromatography, High Pressure Liquid; D015195:Drug Design; D006860:Hydrogen Bonding; D006863:Hydrogen-Ion Concentration; D008958:Models, Molecular; D015394:Molecular Structure; D019906:Nuclear Magnetic Resonance, Biomolecular; D010455:Peptides / Q000737:chemistry* / Q000302:isolation & purification; D011487:Protein Conformation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D011522:Protons; D012996:Solutions / Q000737:chemistry; D012997:Solvents / Q000737:chemistry; D014270:Trifluoroethanol / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
chemical_list: D002247:Carbon Isotopes; D010455:Peptides; D011522:Protons; D012996:Solutions; D012997:Solvents; D014867:Water; D014270:Trifluoroethanol