NUCLEAR MAGNETIC RESONANCE--NEW METHODS AND MOLECULAR STRUCTURE DETERMINATION

我们继续研究溶解在非常稀的向列液晶（LC）相中的生物大分子。在LC介质中对蛋白质泛素中质子、碳和氮主链原子的化学位移（CSA）进行了研究，发现CSA与蛋白质二级结构之间存在明显的相关性。在LC粒子接近中性的情况下，已经开发了一种定量预测已知形状的大分子排列的方法。这一信息证实了溶液中抗hiv蛋白cyanovirin-N的单体形式。方法已经发展，允许测量偶极耦合在缓慢翻滚的大分子。我们已经证明，在有利的情况下，如果可以在两种不同的LC介质中进行测量，则可以仅根据其偶极偶联来定义蛋白质骨架的三维结构。这一发展具有显著减少测定蛋白质结构所需时间的潜力。偶极偶联用于测定RecA结合蛋白DinI的结构，并获得DNA十二聚体d(CGCGAATTCGCG)2的高分辨率结构。

We have continued our study of biological macromolecules dissolved in a very dilute, nematic liquid crystalline (LC) phase. Study of chemical shift aniostropy (CSA) of proton, carbon and nitrogen backbone atoms in the protein ubiquitin, dissolved in a LC medium, revealed distinct correlations between CSA and protein secondary structure. A method has been developed that quantitatively predicts alignment of macromolecules of known shape for the case where the LC particles are nearly neutral. This information confirmed the monomeric form of the anti-HIV protein cyanovirin-N in solution. Methods have been developed that permit measurement of dipolar couplings in slowly tumbling macromolecules. We have shown that in favorable cases it is possible to define the three-dimensional structure of a protein backbone solely on the basis of its dipolar couplings, provided that measurements can be performed in two different LC media. This development holds potential to significantly decrease the time required for protein structure determination. Dipolar couplings were used for determination of the structure of the RecA binding protein DinI, and for obtaining a high-resolution structure of the DNA dodecamer d(CGCGAATTCGCG)2.