肽N-Boc-L-脯氨酸-脱氢苯丙氨酸-L-甘氨酸-OH的合成、晶体结构及分子构象

Synthesis, crystal structure, and molecular conformation of peptide N-Boc-L-Pro-dehydro-Phe-L-Gly-OH.

作者信息

Patel H C, Singh T P, Chauhan V S, Kaur P

机构信息

Department of Biophysics, All India Institute of Medical Sciences, New Delhi.

出版信息

Biopolymers. 1990 Feb 15;29(3):509-15. doi: 10.1002/bip.360290306.

DOI:10.1002/bip.360290306

PMID:2331513

Abstract

The peptide N-Boc-L-Pro-dehydro-Phe-L-Gly-OH was synthesized by the usual workup procedure and finally coupling the N-Boc-L-Pro-dehydro-Phe to glycine. The peptide crystallizes in monoclinic space group P2(1) with a = 8.951(4) A, b = 5.677(6) A, c = 21.192(11) A, beta = 96.97(4) degrees, V = 1069(1) A3, Z = 2, dm = 1.295(5) Mgm-3, and dc = 1.297(4) Mgm-3. The structure was determined by direct methods using SHELXS86. The structure was refined by the block-diagonal least-squares procedure to an R value of 0.074 for 1002 observed reflections. The C alpha 2-C beta 2 distance of 1.33(2) A is an appropriate double bond length. The angle C alpha 2-C beta 2-C gamma 2 is 133(1) degrees. The peptide backbone torsion angles are theta 1 = -167(1) degrees, omega 0 = 179(1) degrees, phi 1 = -48(1) degrees, psi 1 = 137(1) degrees, omega 1 = 175(1) degrees, phi 2 = 65(2) degrees, psi 2 = 15(2) degrees, omega 2 = -179(1) degrees, and phi 3 = -166(1) degrees. These values show that the Boc group has a trans-trans conformation while the peptide backbone adopts a beta-turn II conformation, which is stabilized by an intramolecular hydrogen bond of length of 3.05(1) A. The structures of dehydro-Phe containing peptides suggest that the dehydro-Phe promotes the beta-turn II conformation. The five-membered pyrrolidine ring of the Pro residue adopts an ideal C gamma-exo conformation with torsion angles chi 1(1) = -24(1) degrees, chi 2(1) = 34(1) degrees, chi 3(1) = -30(1) degrees, chi 4(1) = 15(1) degrees, and theta 0(1) = 6(1) degrees. The side-chain torsion angles in dehydro-Phe are chi 1(2) = -1(2) degrees, chi 2,1(2) = -176(1) degrees, and chi 2,2(2) = 8(2) degrees. The plane of C alpha 2-C beta 2-C gamma 2 is rotated with respect to the plane of the phenyl ring at 7(1) degrees, which indicates that the atoms of the side chain of dehydro-Phe are essentially coplanar. The molecules form a 2(1) screw axis related hydrogen-bonded rows along the b axis.

摘要

肽N - Boc - L - Pro - dehydro - Phe - L - Gly - OH通过常规后处理程序合成，最后将N - Boc - L - Pro - dehydro - Phe与甘氨酸偶联。该肽以单斜晶系空间群P2(1)结晶，a = 8.951(4) Å，b = 5.677(6) Å，c = 21.192(11) Å，β = 96.97(4)°，V = 1069(1) Å³，Z = 2，dm = 1.295(5) Mgm⁻³，dc = 1.297(4) Mgm⁻³。结构通过使用SHELXS86的直接法确定。结构通过块对角最小二乘法精修，对于1002个观察反射，R值为0.074。Cα2 - Cβ2距离为1.33(2) Å，是合适的双键长度。角Cα2 - Cβ2 - Cγ2为133(1)°。肽主链扭转角为θ1 = -167(1)°，ω0 = 179(1)°，φ1 = -48(1)°，ψ1 = 137(1)°，ω1 = 175(1)°，φ2 = 65(2)°，ψ2 = 15(2)°，ω2 = -179(1)°，φ3 = -166(1)°。这些值表明Boc基团具有反式 - 反式构象，而肽主链采用β - 转角II构象，该构象通过长度为3.05(1) Å的分子内氢键稳定。含dehydro - Phe的肽的结构表明dehydro - Phe促进β - 转角II构象。Pro残基的五元吡咯烷环采用理想的Cγ - 外向构象，扭转角χ1(1) = -24(1)°，χ2(1) = 34(1)°，χ3(1) = -30(1)°，χ4(1) = 15(1)°，θ0(1) = 6(1)°。dehydro - Phe中的侧链扭转角为χ1(2) = -1(2)°，χ2,1(2) = -176(1)°，χ2,2(2) = 8(2)°。Cα2 - Cβ2 - Cγ2平面相对于苯环平面旋转7(1)°，这表明dehydro - Phe侧链的原子基本共面。分子沿着b轴形成与氢键相关的2(1)螺旋轴行。