Ying Jinfa, Grishaev Alexander, Latham Michael P, Pardi Arthur, Bax Ad
Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
J Biomol NMR. 2007 Oct;39(2):91-6. doi: 10.1007/s10858-007-9181-7. Epub 2007 Aug 7.
For base-paired nucleic acids, variations in (1) J (NH) and the imino (1)H chemical shift are both dominated by hydrogen bond length. In the absence of molecular alignment, the (1) J (NH) coupling for the imino proton then can be approximated by (1) J (NH) = (1.21Hz/ppm)delta(H) - 103.5 +/- 0.6 Hz, where delta(H) represents the chemical shift of the imino proton in ppm. This relation permits imino residual dipolar couplings (RDCs) resulting from magnetic susceptibility anisotropy (MSA) to be extracted from measurement of ((1) J (NH) + RDC) splittings at a single magnetic field strength. Magnetic field-induced RDCs were measured for tRNA(Val) and the alignment tensor determined from magnetic-field alignment of tRNA(Val) agrees well with the tensor calculated by summation of the MSA tensors of the individual nucleobases.
对于碱基配对的核酸，（1）J（NH）和亚氨基（1）H化学位移的变化均由氢键长度主导。在不存在分子排列的情况下，亚氨基质子的（1）J（NH）耦合可以近似表示为（1）J（NH） = （1.21Hz/ppm）δ（H） - 103.5 ± 0.6 Hz，其中δ（H）表示以ppm为单位的亚氨基质子的化学位移。这种关系使得可以通过在单个磁场强度下测量（（1）J（NH） + RDC）分裂来提取由磁化率各向异性（MSA）产生的亚氨基剩余偶极耦合（RDC）。测量了tRNA（Val）的磁场诱导RDC，并且根据tRNA（Val）的磁场排列确定的排列张量与通过各个核碱基的MSA张量求和计算得到的张量非常吻合。
