Grage Stephan L, Suleymanova Aliya V, Afonin Sergii, Wadhwani Parvesh, Ulrich Anne S
Institute of Biological Interfaces, Forschungszentrum Karlsruhe, P.O. Box 3640, 76021 Karlsruhe, Germany.
J Magn Reson. 2006 Nov;183(1):77-86. doi: 10.1016/j.jmr.2006.07.012. Epub 2006 Aug 21.
Dipolar couplings contain information on internuclear distances as well as orientational constraints. To characterize the structure of the antimicrobial peptide gramicidin S when bound to model membranes, two rigid 4-CF3-phenylglycine labels were attached to the cyclic backbone such that they reflect the behavior of the entire peptide. By solid state 19F NMR we measured the homonuclear dipolar couplings of the two trifluoromethyl-groups in oriented membrane samples. Using the CPMG experiment, both the strong couplings within each CF3-group as well as the weak coupling between the two CF3-groups could be detected. An intra-CF3-group dipolar coupling of 86 Hz and a weak inter-group coupling of 20 Hz were obtained by lineshape simulation of the complex dipolar spectrum. It is thus possible to explore the large distance range provided by 19F-labels and to resolve weak dipolar couplings even in the presence of strong intra-CF3 couplings. We applied this approach to distinguish and assign two epimers of the labeled gramicidin S peptide on the basis of their distinct 19F dipolar coupling patterns.
偶极耦合包含有关核间距离以及取向限制的信息。为了表征抗菌肽短杆菌肽S与模型膜结合时的结构，将两个刚性的4-三氟甲基苯甘氨酸标签连接到环状主链上，以便它们反映整个肽的行为。通过固态19F核磁共振，我们测量了取向膜样品中两个三氟甲基基团的同核偶极耦合。使用CPMG实验，可以检测到每个CF3基团内的强耦合以及两个CF3基团之间的弱耦合。通过对复杂偶极谱的线形模拟，获得了CF3基团内86 Hz的偶极耦合和20 Hz的弱基团间耦合。因此，即使在存在强CF3内耦合的情况下，也可以探索由19F标签提供的大距离范围并解析弱偶极耦合。我们应用这种方法，根据标记的短杆菌肽S肽的不同19F偶极耦合模式来区分和指定两个差向异构体。
