NUCLEAR MAGNETIC RESONANCE--NEW METHODS AND MOLECULAR STRUCTURE DETERMINATION

偶极耦合不是平均为零的分子 显著的磁化率各向异性。这种偶极耦合 已测量到GATA1-DNA结合域，与 DNA的16个碱基的片段。添加偶极耦合约束 被证明导致了质量的相当大的改善 结构，并首次允许定位 通过长距离NOE相互作用连接的蛋白质。磁性 观察到了核共振频率的场依赖关系 首次在溶液中进行核磁共振，并获得了GATA1-DNA的结果 复合体确认结构质量在添加后的改善 偶极约束。新的测量方法被开发出来 ~1H和~(13)C化学位移各向异性(CSA)。两者之间的相关性 通过比较1HN CSA得到了酰胺质子CSA和氢键长度 人泛素与其氢键长度的关系 X射线晶体结构。13Ca碳的CSA张量被发现为 强烈依赖于多肽主链角度，f和y，以及 ~(13)Ca-CsA的测定可能会提高 蛋白质结构显著。其他新开发的方法 主链角度f的测量表明，酰胺的N-H键，on 平均，与C‘-N-Ca平面的夹角小于60度， 证实了多肽键的高度平面性 与理论计算的结果相矛盾。

Dipolar couplings do not average to zero for molecules with a significant magnetic susceptibility anisotropy. Such dipolar couplings to have been measured for the GATA1-DNA binding domain, complexed with a 16-basepair fragment of DNA. Addition of dipolar coupling constraints was shown to result in a considerable improvement in the quality of the structure and to allow, for the first time, positioning of elements of the protein that are connected by long range NOE interactions. Magnetic field dependence of the nuclear resonance frequencies was observed for the first time in solution NMR, and results obtained for the GATA1-DNA complex confirm the improvement in structural quality upon addition of the dipolar constraints. New methods were developed for measurement of 1H and 13C chemical shift anisotrphy (CSA). A correlation between amide proton CSA and hydrogen bond length was found by comparing 1HN CSA values in human ubiquitin with hydrogen bond lengths obtained from its X-ray crystal structure. The CSA tensor for 13Ca carbons was found to depend strongly on the polypeptide backbone angles, f and y, and measurement of the 13Ca CSA potentially could increase the quaity of protein structures significantly. Other newly developed methods for measurement of the backbone angles f show that the amide N-H bond, on average, makes an angle of less than 6o with the C'-N-Ca plane, confirming the high degree of planarity for peptide bonds and contradicting the results of theoretical calculations.