Inclusion of residual dipolar couplings (RDCs) during the early rounds of protein structure determination requires use of a floating alignment tensor or knowledge of the alignment tensor strength and rhombicity. For proteins with interdomain motion, such analysis can falsely hide the presence of domain dynamics. We demonstrate for three proteins, maltotriose-ligated maltose binding protein (MBP), Ca2+-ligated calmodulin, and a monomeric N-terminal deletion mutant of the SARS-CoV-2 Main Protease, MPro, that good alignment tensor estimates of their domains can be obtained from RDCs measured for residues that are identified as α-helical based on their chemical shifts. The program, Helix-Fit, fits the RDCs to idealized α-helical coordinates, often yielding a comparable or better alignment tensor estimate than fitting to the actual high-resolution X-ray helix coordinates. The 13 helices of ligated MBP all show very similar alignment tensors, indicative of a high degree of order relative to one another. By contrast, while for monomeric MPro the alignment strengths of the five helices in the C-terminal helical domain (residues 200-306) are very similar, pointing to a well-ordered domain, the single α-helix Y54-I59 in the N-terminal catalytic domain (residues 10-185) aligns considerably weaker. This result indicates the presence of large amplitude motions of either Y54-I59 or of the entire N-terminal domain relative to the C-terminal domain, contrasting with the high degree of order seen in the native homodimeric structure.

Yang Shen

Marshall J Smith

John M Louis

Ad Bax

Journal of Biomolecular NMR

JOURNAL OF BIOMOLECULAR NMR 为发表关于核磁共振波谱技术发展和创新应用的研究提供了一个论坛，用于研究溶液、液晶、固体和混合环境中生物聚合物的结构和动态特性，例如附着在膜上。这可能包括：通过 NMR 对生物大分子（多肽/蛋白质、DNA、RNA、寡糖）进行三维结构测定。用于研究生物大分子的新 NMR 技术。计算机辅助自动分析多维 NMR 光谱的新方法。计算方法用于核磁共振数据的结构解释，包括结构细化。核磁共振确定的结构与其他方法获得的结构的比较，例如通过蛋白质单晶衍射技术。用于核磁共振实验的样品制备新技术（同位素标记的生物合成和化学方法，生物合成同位素标记的营养物质制备等）。必须包括产品的 NMR 表征。

The Journal of Biomolecular NMR provides an important forum for the publication of research on the development and innovative applications of nuclear magnetic resonance (NMR) spectroscopy. It focuses on the study of the structural and dynamic properties of biopolymers in solution, liquid crystal, solid, and mixed environments, including those attached to membranes. The journal may include topics such as: three-dimensional structure determination of biomacromolecules (peptides/proteins, DNA, RNA, oligosaccharides) using NMR; new NMR techniques for studying biomacromolecules; computer-assisted automated analysis methods for multidimensional NMR spectra; computational methods for structural interpretation of NMR data, including structure refinement; comparisons of structures determined by NMR with those obtained through other methods, such as protein single-crystal diffraction; and new techniques for sample preparation for NMR experiments (including isotopically labeled biosynthesis and chemical methods, and preparation of isotopically labeled nutrients through biosynthesis). All research findings must include NMR characterization of the products.

《Journal of Biomolecular NMR》为研究核磁共振波谱技术的发展与创新应用提供了一个重要的论坛，专注于生物聚合物在溶液、液晶、固体及混合环境中的结构与动态特性研究，例如膜上附着的生物聚合物。该期刊的内容可能包括：利用核磁共振（NMR）对生物大分子（如多肽/蛋白质、DNA、RNA、寡糖）进行三维结构测定；新型NMR技术在生物大分子研究中的应用；计算机辅助的多维NMR光谱自动分析新方法；用于核磁共振数据结构解释的计算方法，包括结构细化；通过蛋白质单晶衍射技术获得的结构与NMR确定的结构的比较；以及用于核磁共振实验的样品制备新技术（如同位素标记的生物合成和化学方法，生物合成同位素标记的营养物质制备等）。所有研究成果必须包括产品的NMR表征。

Category	Quartile
生物学	3
生物学, 光谱学	2
生物学, 生化与分子生物学	3

Alpha-helices as alignment reporters in residual dipolar coupling analysis of proteins

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