DEVELOPMENT OF HIGH-RESOLUTION SOLID-STATE NMR

高分辨率固态核磁共振的发展

• 批准号: 7355294
• 负责人: JACOB SCHAEFER
• 金额: $ 0.03万
• 依托单位: WASHINGTON UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-02-01 至 2007-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7355294
• 关键词: DEVELOPMENT; RESOLUTION; SOLID; STATE; NMR

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. In the last 20 years, the combination of cross polarization for sensitivity and magic-angle spinning (with dipolar decoupling) for resolution has made 13C NMR a standard tool for the characterization of solid polymers. Local structure is revealed by 13C chemical shifts and local dynamics from a variety of relaxation measurements in both the laboratory and rotating reference frames. Some success has been achieved in relating these microscopic parameters to macroscopic properties of the polymers. Nevertheless, this important connection is hampered by the fact that conventional 13C NMR spectra must be interpreted primarily in terms of a single chain with the effects of neighboring chains inferred indirectly. However, an accurate, direct characterization of the interchain packing in solid, glassy polymers is crucial to the understanding of the mechanical properties of the polymers. Today, the distances between packed chains can be determined by the same types of rotational-echo double resonance (REDOR) NMR experiments developed for proteins and protein complexes. REDOR NMR for an I-S spin pair involves the dephasing of transverse S-spin magnetization by rotor-synchronized I-spin pi pulses. Coupling to abundant protons is removed using a third radio frequency channel. The results of REDOR experiments lead directly to the strength of the heteronuclear I-S dipolar coupling and hence I-S internuclear distances. In applications on glassy polymers, polycarbonate chains with 13C labels have been mixed with chains having 2H labels. The resulting distances determined by 13C-2H REDOR NMR define local packing geometry on a system for which diffraction experiments are impossible. Interfaces of blends of heterogeneous polymers like poly(p-fluorostyrene) and 13C-labeled polycarbonate can also be characterized quantitatively and accurately by REDOR NMR as shown in the figure below. The residual protons in perdeuterated polymers behave as a rare spin, and REDOR between isolated 1H-13C pairs in perdeuterated poly-carbonate reveals the average location of the ubiquitous 0.3% (by weight) water in glassy polycarbonate.

该子项目是利用NIH/NCRR资助的中心赠款提供的资源的许多研究子项目之一。子弹和调查员（PI）可能已经从其他NIH来源获得了主要资金，因此可以在其他清晰的条目中代表。列出的机构适用于该中心，这不一定是调查员的机构。在过去的20年中，用于敏感性的交叉极化和分辨率的魔术角旋转（带有偶性解耦）使13C NMR成为表征固体聚合物的标准工具。 13C化学位移和局部动力学从实验室和旋转参考框架中的各种松弛测量中揭示了局部结构。将这些微观参数与聚合物的宏观特性相关联，已经取得了一些成功。然而，这种重要的联系受到了以下事实，即必须主要根据单个链来解释传统的13C NMR光谱，并间接地通过相邻链的影响来解释。但是，固体玻璃聚合物中链链填料的准确，直接表征对于理解聚合物的机械性能至关重要。如今，填充链之间的距离可以由相同类型的旋转回声双共振（重复）NMR实验确定，用于蛋白质和蛋白质复合物。 I-S旋转对的重新旋转NMR涉及通过转子同步I-Spin Pi脉冲对横向S-Spin磁化的脱位。使用第三个射频通道去除与丰富质子的耦合。重新实验的结果直接导致异核I-S偶极耦合的强度，从而导致I-S内核距离。在玻璃状聚合物的应用中，具有13C标签的聚碳酸酯链已与具有2H标签的链混合。由13C-2H REDOR NMR确定的结果距离定义了衍射实验的系统上的局部填料几何形状。如下图所示，还可以通过重新的NMR定量，准确地对异质聚合物（Poly（P-氟洛替扬烯）和13C标记的聚碳酸酯）的混合物界面进行定量和准确的表征。 perdeerated聚合物中的残留质子表现为一种罕见的自旋，并且在perdeuterated聚碳酸盐中孤立的1H-13C对之间的重新质量显示出无处不在的0.3％（按重量）水在玻璃状聚碳酸酯中的平均位置。