Department of Chemistry, Columbia University, 3000 Broadway, New York, New York 10027, USA.
J Am Chem Soc. 2011 Dec 21;133(50):20208-17. doi: 10.1021/ja2043062. Epub 2011 Nov 30.
Solid-state NMR spectra, including dynamic nuclear polarization enhanced 400 MHz spectra acquired at 100 K, as well as non-DNP spectra at a variety of field strengths and at temperatures in the range 213-243 K, have allowed the assignment of the (13)C and (15)N resonances of the unusual DNA structure in the Pf1 virion. The (13)C chemical shifts of C3' and C5', considered to be key reporters of deoxyribose conformation, fall near or beyond the edges of their respective ranges in available databases. The (13)C and (15)N chemical shifts of the DNA bases have above-average values for AC4, AC5, CC5, TC2, and TC5, and below average values for AC8, GC8, and GN2, pointing to an absence of Watson-Crick hydrogen bonding, yet the presence of some type of aromatic ring interaction. Crosspeaks between Tyr40 of the coat protein and several DNA atoms suggest that Tyr40 is involved in this ring interaction. In addition, these crosspeak resonances and several deoxyribose resonances are multiply split, presumably through the effects of ordered but differing interactions between capsid protein subunits and each type of nucleotide in each of the two DNA strands. Overall, these observations characterize and support the DNA model proposed by Liu and Day and refined by Tsuboi et al., which calls for the most highly stretched and twisted naturally occurring DNA yet encountered.
固态 NMR 谱，包括在 100 K 下获得的动态核极化增强的 400 MHz 谱，以及在各种场强和温度 213-243 K 范围内获得的非 DNP 谱，允许 Pf1 病毒粒子中异常 DNA 结构的 (13)C 和 (15)N 共振的归属。被认为是脱氧核糖构象关键报告者的 C3'和 C5'的 (13)C 化学位移接近或超出了可用数据库中各自范围的边缘。DNA 碱基的 (13)C 和 (15)N 化学位移对于 AC4、AC5、CC5、TC2 和 TC5 来说是平均值以上，对于 AC8、GC8 和 GN2 来说是平均值以下，这表明不存在 Watson-Crick 氢键，但存在某种类型的芳环相互作用。衣壳蛋白的 Tyr40 与几个 DNA 原子之间的交叉峰表明 Tyr40 参与了这种环相互作用。此外，这些交叉峰共振和几个脱氧核糖共振被多次分裂，可能是由于衣壳蛋白亚基与每一种核苷酸之间的有序但不同的相互作用的影响。总的来说，这些观察结果描述并支持了 Liu 和 Day 提出并由 Tsuboi 等人改进的 DNA 模型，该模型需要遇到的最高度拉伸和扭曲的天然存在的 DNA。
