Deuterium quadrupole coupling in N-acetylglycine and librational dynamics in solid poly(gamma-benzyl-L-glutamate).
Deuterium quadrupole coupling in N-acetylglycine and librational dynamics in solid poly(gamma-benzyl-L-glutamate).
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N-乙酰甘氨酸中的氘四极耦合和固体聚（γ-苄基-L-谷氨酸）中的解放动力学。
DOI：
10.1021/bi00230a022
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发表时间：
1991
期刊：
影响因子：
2.9
通讯作者：
Wittebort,RJ
中科院分区：
文献类型：
--
作者：
Usha,MG;Peticolas,WL;Wittebort,RJ
摘要：为了研究固体蛋白质中多肽基团的动力学，我们用单晶氘核磁共振技术准确地测定了单斜/V-乙酰甘氨酸中可交换的质子的电场梯度张量的主成分和分子取向。这些结果与在很宽的温度范围内(140K-400K)粉末样品中测得的固体聚(Y-苄基-L-谷氨酸)中的胺氚的主成分进行了比较。比较表明，在固体多肽中，ND键经历了垂直于多肽平面的小幅度扭转重新取向(振动)。为了估计动态速率，报道了/V-乙酰甘氨酸和聚谷氨酸苄酯的纵向弛豫时间(7)。/V-乙酰甘氨酸中的羧基和氨基的氚的Tx值为-100 S，而多肽Tx~1中的氨基的Tx值为-100 S，这也表明多肽中的ND键是不稳定的。我们由折合的四极耦合张量确定了振动的均方振幅，并表明它随温度线性增加。本文给出了一个简单的关于弛豫时间的定性理论，该理论假定ND的重定向过程可以描述为方势垒中的扩散过程，也可以描述为具有简谐恢复力的阻尼朗之万振子。结果表明，多肽酰胺的弛豫时间较短是由于摩擦对重取向的影响，且摩擦效应随温度的升高而增大。
Revised Manuscript Received December 17, 1990 abstract: To study the dynamics of peptide groups in solid proteins, we have accurately determined the principal components and molecularorientation of the electricfield gradient tensor for the exchangeable deuterons in monoclinic/V-acetylglycine by single-crystal deuterium nuclear magnetic resonance. These results are compared with the principal components of the amide deuterons in solid poly (Y-benzyl-L-glutamate) measured in powder samples over a wide temperature range (140-400 K). The comparison indicates that in the solid polypeptide the ND bonds undergo a small-amplitude torsional reorientation (libration) perpendicular to the peptide plane. To estimate dynamic rates, longitudinal relaxation times (7, values) are reported for/V-acetylglycine and poly (-benzyl-L-glutamate). Tx values for the carboxyl and amide deuterons in/V-acetylglycine are—100 s, whereas for the amide deuterons in the polypeptide Tx~ 1 s, also indicating that the ND bonds are not stationary in the polypeptide. We determine from thereduced quadrupole coupling tensor the mean-square amplitude for the libration and show that it increases linearly with temperature. A simple qualitative theory for the relaxation times is presented on the basis of the assumption that the ND reorientation is described either as a diffusion process in a square well or as a damped Langevin oscillatorwith a harmonic restoring force. The conclusion is that the short relaxation times of the polypeptide amide deuterons result from substantial frictional effects on reorientation that increase with temperature.