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。31P化学位移各向异性及31P- h3 ？偶极偶联独立验证了由偶极偶联导出的模型DNA寡核苷酸的结构比传统的核磁共振结构或晶体状态下观察到的结构要精确得多。示踪剂扩散各向异性测量表明，常用的二束液晶介质不是由圆盘组成，而是由强穿孔双层组成。对最近提出的凝胶排列大分子方法的一种改进已经开发出来，允许拉伸凝胶而不是压缩凝胶。这是首次证明了洗涤剂溶解多肽可以在这种介质中排列，为研究这种系统提供了新的机会。钙钙调蛋白的偶极偶联研究表明，n端结构域的螺旋角与晶体状态下观察到的螺旋角有很大不同，表明这种调节蛋白具有相当大的可塑性。相比之下，大多数靶相互作用残基的侧链chi-1角被锁定为单一的旋美态，8个蛋氨酸残基的chi-2和chi-3角的灵活性主导了靶相互作用表面的局部可塑性。

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.