Variable NMR Spin−Lattice Relaxation Times in Secondary Amides: Effect of Ramachandran Angles on Librational Dynamics†
Variable NMR Spin−Lattice Relaxation Times in Secondary Amides: Effect of Ramachandran Angles on Librational Dynamics†
复制标题
仲酰胺中可变 NMR 自旋晶格弛豫时间：拉马钱德兰角对解放动力学的影响†
DOI：
10.1021/jp971068c
复制
发表时间：
1998
影响因子：
3.3
通讯作者：
A. McDermott
中科院分区：
文献类型：
--
作者：
John C. Williams‡ and;A. McDermott
N-氘代微晶仲酰胺的氘NMR自旋晶格弛豫时间（T1 Z）在室温下从小于1 s到大于500 s不等。影响弛豫的主要运动是酰胺的平面外振动，如由温度依赖性线形和各向异性弛豫谱所示。超过25个酰胺进行了测量，他们不同的侧链立体，氢键长度，氢键几何形状，和晶体包装。温度依赖性氘线形状和各向异性弛豫速率表明约10°的面外角偏转;快速和缓慢弛豫酰胺的角度可能相似，而运动的表观时间常数可能变化很大。辛内酰胺和己内酰胺的酰胺基两侧亚甲基中的氘也表明了面外振动，其弛豫速率比酰胺氘快，这可能是因为扭曲的角范围比酰胺氘的弛豫速率大。
Deuterium NMR spin−lattice relaxation times (T1Z) of N-deuterated microcrystalline secondary amides vary from less than 1 s to more than 500 s at room temperature. The main motion effecting relaxation is an out-of-plane libration of the amide, as indicated by temperature-dependent line shapes and anisotropic relaxation spectra. Over 25 amides were measured; they vary with respect to side chain sterics, hydrogen bond lengths, hydrogen bond geometry, and crystal packing. The temperature-dependent deuterium line shape and anisotropic relaxation rates indicate an out-of-plane angular deflection of approximately 10°; the angle is probably similar for the rapidly and slowly relaxing amides, while the apparent time constant for the motion probably varies dramatically. Deuterons in methylene groups on both sides of the amide group for caprylolactam and caprolactam also indicate an out-of-plane libration with relaxation rates faster than that of the amide deuteron, probably because the angular extent of the distor...