BASE TILTS IN POLYNUCLEOTIDES FROM FLOW LINEAR DICHROISM

本研究的总体目标是探索其构象 溶液中的多核苷酸和核酸，它们很可能是 与它们在晶体和纤维中的构象不同。事实上，研究 不同DNA的每一轮的碱基对数量表明这一点 参数是灵活的，它随序列而变化，当然不是 完整的10倍重复，最初发现用于B型纤维。此外， 许多研究表明，碱基对具有公平的倾向性。 即使在B形解条件下也是与螺旋轴的夹角。在这里我们 建议恢复真空紫外线性二色性(LD)研究 确定碱基相对于螺旋倾斜的角度 在不同的碱基序列和不同的溶液条件下。在……里面 一种碱基的螺旋核酸流动LD实验， 有三个未知数：底座的倾斜度，方位 底座绕其倾斜的轴线，以及底座倾斜的系数 聚合物在流动中的对准。如果存在不止一种类型的 碱基在核酸中，那么每种类型的碱基都可能有不同的 倾斜度和轴线。我们实验室已经开发出一种特殊的流线型 将在真空中进行测量的二色性仪器 紫外区使数据的信息含量 足以解决所有的未知数。在以前的工作中，我们 测定了一些简单脱氧多核苷酸的倾斜角，以及 对于DNA本身来说。我们现在要研究水溶液中的简单核多核苷酸 溶液，以及在溶液条件下的简单脱氧核苷酸 请出示A表。此外，我们还建议准确地确定 A-型DNA每一轮的碱基对数。然后，我们将使用新的 基座倾角和螺旋线重复数据计算相应 真空紫外CD光谱。这些计算的光谱将被比较 与CD光谱测量进入真空紫外区在我们的特殊 仪器仪表。此外，我们还会比较质子间距离 在这些新的螺旋重复序列的碱基和碱基倾斜之间 从现代2D核磁共振工作的NOESY数据中获得的值。已被占用 总而言之，这项工作对于确定真正的基地应该是有价值的 多核苷酸和核酸在溶液中的取向。

The overall aim of this research is to probe the conformation of polynucleotides and nucleic acids in solution, which may well be different from their conformation in crystals and fibers. Indeed, studies on the number of base pairs per turn for various DNAs indicate that this parameter is flexible, varying with sequence and certainly not the integral 10-fold repeat originally found for B-form fibers. Furthermore, a number of studies indicate that the base pairs make a fair inclination angle with the helix axis even under B-form solution conditions. Here we propose to resume our vacuum ultraviolet linear dichroism (LD) studies to determine the angle at which bases are inclined with respect to he helix axis for various base sequences and under various solution conditions. IN a flow LD experiment on helical nucleic acids with one type of basis, there are three unknowns: the inclination of the bases, the orientation of the axis around which the bases are inclined, and the coefficient for alignment of the polymer in the flow. If there is more than one kind of base in the nucleic acid, then each type of base may have a different inclination and axis. Our laboratory had developed a special flow linear dichroism instrument that will make measurements into the vacuum ultraviolet region so that the information content of the data is sufficient to solve for all of the unknowns. In previous work we determined inclination angles for some simple deoxypolynucleotides, and for DNA itself. We would now study simple ribopolynucleotides in aqueous solution, and simple deoxyribonucleotides under solution conditions that produce the A form. Furthermore, we propose to determine accurately the number of base pairs per turn for A-form DNA. We would then use the new base inclination and helix repeat data to calculate the corresponding vacuum ultraviolet CD spectra. These calculated spectra would be compared with CD spectra measured into the vacuum UV region on our special instrumentation. Furthermore, we would compare the interproton distances between the bases for these new helical repeats and base inclinations to the values obtained form NOESY data from modern 2D NMR work. Taken together, this work should be valuable for determining the true base orientation for polynucleotides and nucleic acids in solution.