title: Crystal and molecular structure of L-valyl-L-lysine hydrochloride.
abstract: L-Valyl-L-lysine hydrochloride, C11N3O3H23 HCl, crystallizes in the monoclinic space group P2(1) with a = 5.438(5), b = 14.188(5), c = 9.521(5) A, beta = 95.38(2) degrees and Z = 2. The crystal structure, solved by direct methods, refined to R = 0.036, using full matrix least-squares method. The peptide exists in a zwitterionic form, with the N atom of the lysine side-chain protonated. The two gamma-carbons of the valine side-chain have positional disorder, giving rise to two conformations, chi 1(11) = -67.3 and 65.9 degrees, one of which (65.9 degrees) is sterically less favourable and has been found to be less popular amongst residues branching at beta-C. The lysine side-chain has the geometry of g- tgt, not seen in crystal structures of the dipeptides reported so far. Interestingly, chi 2(3) (63.6 degrees) of lysine side-chain has a gauche+ conformation unlike in most of the other structures, where it is trans. The neighbouring peptide molecules are hydrogen bonded in a head-to-tail fashion, a rather uncommon interaction in lysine peptide structures. The structure shows considerable similarity with that of L-Lys-L-Val HCl in conformational angles and H-bond interactions [4].
authors.affiliation: Department of Physics, Indian Institute of Science, Bangalore.
authors.forename: H P
authors.initials: HP
authors.lastname: Yennawar
authors.forename: S
authors.initials: S
authors.lastname: Natarajan
authors.forename: M A
authors.initials: MA
authors.lastname: Viswamitra
mesh_terms: D004151:Dipeptides / Q000737:chemistry*; D006860:Hydrogen Bonding; D015394:Molecular Structure; D011487:Protein Conformation; D014961:X-Ray Diffraction
chemical_list: D004151:Dipeptides; C074992:valyllysine