Klages Jochen, Neubauer Cajetan, Coles Murray, Kessler Horst, Luy Burkhard
Department Chemie, Lehrstuhl für Organische Chemie II, Technische Universität München, Lichtenbergstrasse 4, 85747 Garching, Germany.
Chembiochem. 2005 Sep;6(9):1672-8. doi: 10.1002/cbic.200500146.
New developments concerning alignment media for apolar solvents like chloroform make it possible to measure anisotropic parameters such as residual dipolar couplings (RDCs) at relatively low concentrations and natural isotopic abundance. As RDCs provide structural restraints with respect to an external coordinate system, long-range structural arrangements of the time-averaged structure can be determined with high precision. The method is demonstrated on the well-studied cyclo-undecapeptide Cyclosporin A (CsA), for which crystal and conventionally derived NMR structures are available. Neither crystal nor NMR structure are consistent with heteronuclear D(CH) RDCs measured in a stretched poly(dimethylsiloxane) gel, and refinement by using the anisotropic parameter results in a highly defined structure with a slightly changed backbone conformation. The applied methods and interpretation of the structural model are discussed.
用于氯仿等非极性溶剂的取向介质的新进展使得在相对低浓度和天然同位素丰度下测量诸如残余偶极耦合（RDC）等各向异性参数成为可能。由于RDC提供了相对于外部坐标系的结构限制，因此可以高精度地确定时间平均结构的远程结构排列。该方法在经过充分研究的环十一肽环孢菌素A（CsA）上得到了验证，已有其晶体结构和传统衍生的NMR结构。晶体结构和NMR结构均与在拉伸聚二甲基硅氧烷凝胶中测量的异核D(CH) RDC不一致，通过使用各向异性参数进行精修得到了具有略微改变的主链构象的高度明确的结构。讨论了所应用的方法和结构模型的解释。
