title: Peptide design: influence of a guest Aib-Pro segment on the stereochemistry of an oligo-val sequence--solution conformations and crystal structure of Boc-(Val)2-Aib-Pro-(Val)3-OMe.
abstract: The peptide Boc-Val-Val-Aib-Pro-Val-Val-Val-OMe has been synthesized to investigate the effect of introduction of a strong beta-turn promoting guest segment into an oligopeptide with a tendency to form extended structures. 1H-nmr studies in solution using analysis of NH group solvent accessibility and nuclear Overhauser effects suggest an appreciable solvent dependence of conformations. In chloroform a 3(10)-helical structure is favored, while in dimethylsulfoxide an Aib-Pro beta-turn with extended arms on either side is suggested. In the crystal, the backbone forms a somewhat distorted 3(10)-helix despite the presence of a Pro residue in the middle. Among the four possible intrahelical hydrogen bonds three are of the 4----1 type and one 5----1. Head-to-tail NH...O = C hydrogen bonds link the helical molecules into continuous columns. The space group is P2(1)2(1)2(1) a = 11.320(2), b = 19.889(3), and c = 21.247(3) A.
authors.affiliation: Laboratory for the Structure of Matter, Naval Research Laboratory, Washington, D.C. 20375-5000.
authors.forename: I L
authors.initials: IL
authors.lastname: Karle
authors.forename: J L
authors.initials: JL
authors.lastname: Flippen-Anderson
authors.forename: K
authors.initials: K
authors.lastname: Uma
authors.forename: H
authors.initials: H
authors.lastname: Balaram
authors.forename: P
authors.initials: P
authors.lastname: Balaram
mesh_terms: D000595:Amino Acid Sequence; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003460:Crystallization; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009842:Oligopeptides; D011487:Protein Conformation; D012996:Solutions
chemical_list: D009842:Oligopeptides; D012996:Solutions