NUCLEAR MAGNETIC RESONANCE--NEW METHODS AND MOLECULAR STRUCTURE DETERMINATION

我们继续研究溶解在非常稀薄的向列型液晶(LC)相中的生物大分子。对蛋白质泛素中质子、碳和氮主链原子在LC介质中的化学位移反转(CSA)的研究表明，CSA与蛋白质的二级结构有明显的相关性。已经开发出一种方法，用于定量预测已知形状的大分子在LC颗粒近中性的情况下的排列。这一信息证实了抗HIV蛋白氰基韦林-N在溶液中的单体形式。已经开发出允许测量缓慢滚动的大分子中的偶极耦合的方法。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，则仅根据蛋白质骨架的偶极耦合来定义其三维结构是可能的。这一进展有可能显著减少蛋白质结构测定所需的时间。偶极偶联用于确定RecA结合蛋白DINI的结构，并获得DNA十二聚体d(CGAATTCGCG)2的高分辨结构。

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.