title: The influence of the stereochemistry of alanine residue on the solid state conformation and crystal packing of opioid peptides containing D-Ala or L-Ala in message domain--XRD and NMR study.
abstract: In this work, an X-ray diffraction (XRD) and solid state NMR study of two tetrapeptides with different stereochemistry of alanine residue is presented using Tyr-(D-Ala)-Phe-Gly (1), an N-terminal sequence of opioid peptide dermorphin, and its biologically inactive analog Tyr-(L-Ala)-Phe-Gly (2). Single-crystal XRD proved that 1 crystallized under different conditions from exclusively one structure: a monoclinic crystal with P2(1) space group. In contrast, 2 very easily formed at least three crystallographic modifications, 2a (monoclinic P2(1)), 2b (orthorhombic P2(1)2(1)2) and 2c (tetragonal P4(1)2(1)2). Solid-state NMR spectroscopy was employed to investigate the structure and molecular dynamics of 1, 2a, and 2b. By employing different NMR experiments (dipolar dephasing and PILGRIM) and an analysis of the (13)C principal elements of the chemical shift tensor (CST), it was proven that the main skeleton of tetrapeptides is rigid, whereas significant differences in the molecular motion of the aromatic residues were observed. Comparing current data with those of previous studies (J. Phys. Chem. B2004, 108, 4535-4545 and Cryst. Growth Des. 2009, 9, 4050-4059), it can be assumed that an important preorganization mechanism anticipating the formation of peptide crystals containing D-Ala in sequence is the intramolecular CH-π interaction, which occurs for the amino acid with D stereochemistry. This effect may be responsible for the formation of only one crystallographic form of D-Ala peptides.
authors: Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Sienkiewicza 112, 90-363 Lodz, Poland.
authors: Katarzyna
authors: K
authors: Trzeciak-Karlikowska
authors: Anna
authors: A
authors: Bujacz
authors: Włodzimierz
authors: W
authors: Ciesielski
authors: Grzegorz D
authors: GD
authors: Bujacz
authors: Marek J
authors: MJ
authors: Potrzebowski
mesh_terms: D000409:Alanine / Q000737:chemistry*; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D018847:Opioid Peptides / Q000737:chemistry*; D011487:Protein Conformation; D013237:Stereoisomerism
chemical_list: D018847:Opioid Peptides; D000409:Alanine