title: NMR and X-ray crystallographic studies on cyclic tetrapeptide, cyclo (D-Phe-Pro-Sar-Gly).
abstract: The conformation of the synthetic cyclic tetrapeptide cyclo(D-Phe-Pro-Sar-Gly) has been determined in solution using the nuclear magnetic resonance technique and in the crystal state by X-ray crystallography. Results showed that the peptide exhibited two different conformations in solution, conformer 1 having cis-trans-cis-trans peptide bonds and conformer 2 having trans-cis-trans-cis peptide bonds. No intramolecular hydrogen bonds were observed in the structures. The X-ray diffraction studies showed the crystals to be orthorhombic with space group P2(1)2(1)2(1) with unit-cell dimensions, a = 5.790, b = 10.344, c = 31.446 A, Z = 4, R = 0.104 for 2301 observed reflections. The crystal structure showed only one type of conformer having cis-trans-cis-trans peptide bonds similar to the conformer 1 in solution.
authors.affiliation: Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India.
authors.forename: D S
authors.initials: DS
authors.lastname: Jois
authors.forename: S
authors.initials: S
authors.lastname: Suresh
authors.forename: M
authors.initials: M
authors.lastname: Vijayan
authors.forename: K R
authors.initials: KR
authors.lastname: Easwaran
mesh_terms: D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D007477:Ions; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D010456:Peptides, Cyclic / Q000737:chemistry* / Q000378:metabolism; D011487:Protein Conformation; D012521:Sarcosine / Q000737:chemistry; D012996:Solutions
chemical_list: D007477:Ions; D010456:Peptides, Cyclic; D012996:Solutions; C102725:cyclo(phenylalanyl-prolyl-sarcosyl-glycyl); D012521:Sarcosine