NMR--New Methods And Molecular Structure Determination

NMR--新方法和分子结构测定

• 批准号: 6983732
• 负责人: Ad - Bax
• 金额: --
• 依托单位: NATIONAL INSTITUTE OF DIABETES AND DIGESTIVE AND KIDNEY DISEASES
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/6983732
• 关键词: biomagnetism measurement; calcium ion; calmodulin; chemical binding; intermolecular interaction; liquid crystal; method development; micelles; nuclear magnetic resonance spectroscopy; nucleic acid structure; protein structure; rhodopsin; structural biology

We have extended our technology for studying macromolecular structure in solution under weakly aligning conditions. New developments focus on the accurate measurement of dipolar interactions between protons. We have demonstrated that under favorable conditions, such direct interactions are observable over distances of up to 12 ?, without requiring special isotopic enrichment. The 1H-1H dipolar interaction depends on both the internuclear distance and on the orientation of the internuclear vector relative to the alignment frame of the molecule, and thereby constitutes a direct complement to the widely used 1H-1H NOE interaction, which depends only on the distance. The combination of 1H-1H dipolar interactions and 1H-13C couplings was shown to be sufficient to accurately define the solution structure of a DNA oligomer, but also showed that in particular the deoxyribose units of pyrimidine nucleotides were not compatible with a single, static conformation. They are, however, in agreement with a model where the sugar rapidly switches between a C2?-endo conformer (the dominant form), and a minor C3?-endo form. Our newly developed experiments permit the accurate measurement of an unprecedented number of dipolar couplings per structural unit (ribose, deoxyribose, or amino acid) and thereby provides a new avenue to explore the degree of alignment each unit experiences individually, thereby providing direct information on the degree of mobility, or lack thereof, of such units relative to the overall frame of the macromolecule. Previous work by others has explored the issue of intramolecular dynamics in nucleic acids on the basis of the observed degree of magnetic alignment, resulting from magnetic susceptibility anisotropy, and the actually observed alignment. Frequently, this led to conclusions that very large amplitude internal dynamics and hinge motions were present in nucleic acids. We have re-analyzed the intrinsic magnetic susceptibility of nucleic acids bases by both quantum-computational and experimental methods and find considerably smaller values than were commonly used by others. With our new base susceptibility values, the amplitude of domain motions in nucleic acids is of considerably smaller amplitude than concluded previously. This finding is of direct relevance for understanding the thermodynamic components in protein-nucleic acid recognition.

我们已经扩展了在弱排列条件下研究溶液中大分子结构的技术。新的发展集中在质子之间的偶性相互作用的准确测量上。我们已经证明，在有利的条件下，这种直接相互作用在高达12？的距离内可观察到，而无需特殊的同位素富集。 1H-1H的偶极相互作用取决于核会内距离和核外载体相对于分子的比对框的方向，从而构成了与广泛使用的1H-1H NOE相互作用的直接补体，这仅取决于距离。 1H-1H偶极相互作用和1H-13C耦合的组合被证明足以准确地定义DNA低聚物的溶液结构，但也表明，特别是氨基酰胺核苷酸的脱氧核糖核酸单位与单个静态构象不符。但是，它们与一个模型一致，在该模型中，糖在C2？-Endo构象异构体（主要形式）和次要C3？-Endo形式之间迅速切换。我们新开发的实验允许准确测量每个结构单元（核糖，脱氧核糖或氨基酸）的前所未有的偶极耦合，从而提供了一个新的途径，以探索每个单位经验的一致性程度，从而提供了有关动机性程度的直接信息，以相对的整体框架提供了整体框架的框架。 其他人的先前工作探索了核酸中分子内动力学的问题，该问题是根据磁敏感性各向异性和实际观察到的比对而导致的磁比对度。通常，这得出结论，核酸中存在非常大的振幅内部动力学和铰链运动。我们通过量子计算和实验方法重新分析了核酸碱基的固有磁敏感性，并发现比其他人通常使用的值要小得多。借助我们新的基础敏感性值，核酸中域运动的振幅比以前得出的幅度要小得多。这一发现对于理解蛋白质核酸识别的热力学成分是直接相关的。