Nuclear Magnetic Resonance--new Methods And Molecular St

我们推广了弱排列条件下核磁共振波谱研究溶液中大分子结构的技术。新的进展集中在一种允许将小角X射线散射数据直接合并到核磁共振结构确定中的程序上。虽然计算成本很高，但使用GLOB？Approach将某些多肽基团视为固定的单点单元，在完整的原子计算中将方法加速了几个数量级。将实验数据结合到结构修正中，对伽马-S晶体蛋白的应用表明，它对同系X射线结构有相当好的拟合度。事实证明，利用SAXS数据研究分子络合物和研究溶液条件下复杂体系的四元结构特别有用。 对洗涤剂胶束中四聚钾通道KCSA的研究表明，如果体系在高温下保持稳定，用核磁共振研究相对较大(65 KDa)的膜蛋白本质上是可行的。核磁共振数据表明，通道/洗涤剂聚集体以扁球体的形式翻滚，反映了洗涤剂分子存在于通常跨越膜的疏水表面。K+结合不受洗涤剂的干扰，在通道的选择性滤域的封闭状态下，没有发现升高的、大幅度的运动的证据。 已经开发了新的实验来表征高度不稳定的质子在RNA中的位置，例如2‘-羟基质子。这些实验明确地揭示了RNA A型螺旋区中的2‘OH质子指向碱基，而不像先前文献报道的那样在C3’区和碱基区之间交替。

We have extended the technology for studying macromolecular structure in solution by NMR spectroscopy under weakly aligning conditions. New developments focus on a procedure that permits direct incorporation of small angle X-ray scattering data into NMR structure determination. Although computationally expensive, use of a ?glob? approach, which treats certain peptide groups as fixed single point units, accelerates the method by several orders of magnitude over a full atom calculation. Application to gamma-S crystallin showed a considerably better fit to homologous X-ray structure upon incorporation of experimental SAXS data in the structure refinement. Use of SAXS data is proving particularly useful for the study of molecular complexes and for studying quaternary structure of complex systems under solution conditions. Study of the tetrameric potassium channel KcsA in detergent micelles indicates that NMR studies of relatively large (65 kDa) membrane proteins intrinsically is feasible by NMR, provided that the system remains stable at elevated temperature. NMR data indicate that the channel/detergent aggregate tumbles as an oblate spheroid, reflecting the presence of detergent molecules on the hydrophobic surface that normally spans the membrane. K+ binding is found not to be disturbed by the presence of detergent, and no evidence for elevated, large amplitude motions is found in the closed state of the so-called selectivity filter domain of the channel. Novel experiments have been developed that permit characterization of the position of highly labile protons such as 2' hydoxyl protons in RNA. These experiments reveal unambiguously that the 2'OH proton in A-form helical regions of RNA points towards the base, and does not alternate between the C3' and base regions, as reported earlier in the literature.