Nuclear Magnetic Resonance--new Methods And Molecular St

我们继续研究相对于磁场弱排列的生物大分子。~（31）P化学位移各向异性和~（31）P-H_3？偶极偶联独立地证实了由偶极偶联衍生的模型DNA寡核苷酸的结构比常规NMR结构或在结晶状态下观察到的结构精确得多。示踪剂扩散各向异性的测量表明，常用的bicellar液晶介质不包括磁盘，但强烈穿孔的双层。最近提出的凝胶法对齐大分子的修改已被开发，允许拉伸的凝胶，而不是压缩。它已被证明第一次，洗涤剂溶解的多肽可以在这样的介质中对齐，提供了新的机会，这样的系统的研究。偶极耦合的钙离子-钙调蛋白的研究表明，螺旋间的角度在N-末端结构域中观察到的结晶状态，表明在这种调节蛋白相当大的可塑性有很大的不同。相比之下，大多数靶相互作用残基的侧链chi-1角被锁定为单个旋转异构体状态，并且靶相互作用表面中的局部可塑性由8个甲硫氨酸残基的chi-2和chi-3角中的柔性主导。

We have continued our study of biological macromolecules that are weakly aligned relative to the magnetic field. Study of 31P chemical shift anisotropy and 31P-H3? dipolar couplings independently validate that the structure derived of a model DNA oligonucleotide derived from dipolar couplings is considerably more accurate than the conventional NMR structure or structures observed in the crystalline state. Tracer diffusion anisotropy measurements indicate that the commonly used bicellar liquid crystalline medium does not consist of disks but of strongly perforated bilayers. A modification to the recently proposed gel method for aligning macromolecules has been developed that permits stretching of the gel instead of compression. It has been demonstrated for the first time that detergent-solubilized polypeptides can be aligned in such a medium, providing new opportunities for the study of such systems. A dipolar coupling study of Ca2+-calmodulin reveals that the interhelical angles in the N-terminal domain differ substantially from those observed in the crystalline state, indicative of considerable plasticity in this regulatory protein. In contrast, the sidechain chi-1 angles of the majority of target-interacting residues are locked into a single rotameric state, and local plasticity in the target-interacting surface is dominated by flexibility in the chi-2 and chi-3 angles of 8 methionine residues.