A15N-1H dipolar CSA solid-state NMR study of polymorphous polyglycine (-CO-CD2-15NH-)n
A15N-1H dipolar CSA solid-state NMR study of polymorphous polyglycine (-CO-CD2-15NH-)n
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多晶型聚甘氨酸 (-CO-CD2-15NH-)n 的 A15N-1H 偶极 CSA 固态 NMR 研究
DOI：
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发表时间：
1999
期刊：
影响因子：
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通讯作者：
G. Buntkowsky
中科院分区：
文献类型：
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作者：
I. Sack;S. Macholl;F. Wehrmann;J. Albrecht;H. Limbach;F. Filiaux;M. Baron;G. Buntkowsky
测量了两种不同修饰的Cα-氘代15N-聚甘氨酸，即PG I和PG II(-CO-CD2-15NH-)n的固态1H MAS(魔角旋转)、2H静态、15N CP(交叉极化)-MAS和15N-1H偶极CSA(化学屏蔽各向异性)NMR(核磁共振)谱。这些光谱数据与之前的核磁共振、红外、拉曼和非弹性中子散射工作进行了比较。 Cα的氘化消除了最大的分子内1H-1H偶极耦合。与 15 N-1H 耦合（约 10 kHz）相比，剩余的（N）H-（N）H 相互作用（～5 kHz）的影响不可忽略。对其描述为双自旋系统的偶极CSA光谱的影响进行了分析和数值分析，并且表明粉末光谱中对应于具有强偶极15N-1H相互作用的取向的那些部分可以被描述为有效的双自旋系统，允许测量15N-1H偶极相互作用的强度以及偶极矢量相对于15NCSA框架的取向。在 PG II 系统中，15N CSA 张量与酰胺平面共线，而在 PG I 系统中，CSA 张量倾斜约 15N CSA 张量。相对于 (δ11δ22) CSA 平面成 16°。
The solid-state1H MAS (magic-angle spinning),2H static,15N CP (cross polarization)-MAS and15N-1H dipolar CSA (chemical shielding anisotropy) NMR (nuclear magnetic resonance) spectra of two different modifications of Cα-deuteratedl5N-polyglycine, namely PG I and PG II (-CO-CD2-l5NH-)n are measured. The data from these spectra are compared to previous NMR, infrared, Raman and inelastic neutron scattering work. The deuteration of Cα eliminates the largest intramolecular1H-1H dipolar coupling. The effect of the remaining (N)H-(N)H interaction (∼5 kHz) is not negligible compared to the15N-1H coupling (about 10 kHz). Its effect on the dipolar CSA spectra, described as a two-spin system, is analyzed analytically and numerically and it is shown that those parts of the powder spectrum, which correspond to orientations with a strong dipolar15N-1H interaction, can be described as an effective two-spin system, permitting the measurement of the strength of the15N-1H dipolar interaction and the orientation of the dipolar vector with respect to the15N CSA frame. While in the PG II system the15N CSA tensor is collinear with the amide plane, in the PG I system the CSA tensor is tilted ca. 16° with respect to the (δ11δ22) CSA plane.