Crystal Structure and Conformation of Short Linear Peptides: Part VI: L‐Alanyl‐L‐Prolyl‐Glycine Monohydrate

Abstract

C10H1,NIOr.H20, H r -261.28, orthorhybic, P212121, a -6.716;1), b = 11.780(1), c -16.248(?)1, Y -1285.6(2)1 , 2 = 4, Dr -1.35 g.cm' , CuKo, A -1.5418 A, u -9.28 cm-, P ( 0 0 0 ) -560, T 291K, R -0.063 for 2447 observed reflections. The molecule (hereafter APG) adop:s a collagen-like conformation at Pro residue with ( 0 2 , $12) values of (-66.6 , 156.9') and an extended form at the two terminal residues. The pyrrolidine ring is disordered with two positions for C(6) : its conformation is C2-CY-ondo for the major component(75%) end C2-Cy-eto for the minor one(250). The geometry and the main-chain conformation are both in excellent agreement with those found in the tripeptide L-Leu-L-Pro-Gly monohydrate (hereafter LPG) It seems that the atoms further than Cy of the Leu side chain do not affect significantly the conformation of peptide backbone in this case. The twofold screw axis in the LPG crystal structure corresponds to that of the APG in the a direction.

Low-Temperature Polymorphic Phase Transition in a Crystalline Tripeptidel-Ala-l-Pro-Gly·H2O Revealed by Adiabatic Calorimetry

“…Tripeptide Ala-Pro-Gly (lot 0513046) was purchased from Bachem (King of Prussia, PA) and recrystallized from water. The crystal structure of the sample (space group P 2 1 2 1 2 1 , Z = 4 , ) was confirmed by single-crystal X-ray diffraction (Siemens three-circle Platform diffractometer) and by powder X-ray diffraction (PANalytical X’Pert Pro multipurpose diffractometer equipped with Oxford Cryosystems PheniX cryostat). The sample purity was >99% (TLC) and in accordance with elemental analysis for anhydrous tripeptide (C 10 H 17 N 3 O 4 ), found/calculated (mass %): C 46.09/45.97, H 7.27/7.33, N 16.01/16.08.…”

“…Tripeptide Ala-Pro-Gly (lot 0513046) was purchased from Bachem (King of Prussia, PA) and recrystallized from water. The crystal structure of the sample (space group P2 1 2 1 2 1 , Z = 4 42,43 ) was confirmed by single-crystal X-ray diffraction (Siemens three-circle Platform diffractometer) and by powder X-ray diffraction (PANalytical X'Pert Pro multipurpose diffractometer equipped with Oxford Cryosystems PheniX cryostat). The sample purity was >99% (TLC) and in A precision adiabatic calorimeter (Block Calorimetric Thermophysical, BCT-3) was used to measure heat capacities over the temperature range from 6 to 320 K. The design and operation of an adiabatic calorimeter are described in detail elsewhere.…”

High-resolution solid-state NMR structure of Alanyl-Prolyl-Glycine

“…Crystal structure of APG [14] showing the 11 SSNMR experimental constraints used in the structural refinement. Torsion angles are displayed in violet, REDOR distances in orange and R 2 W constraints in black.…”