BASE TILTS IN POLYNUCLEOTIDES FROM FLOW LINEAR DICHROISM

本研究的总体目的是探讨 在溶液中的多核苷酸和核酸，其可以很好地 与晶体和纤维中的构象不同。 事实上，研究 对各种DNA每转碱基对数量的研究表明， 参数是灵活的，随序列而变化， 最初在B型纤维中发现完整的10倍重复。 此外，委员会认为， 许多研究表明，碱基对会产生合理的倾斜， 即使在B型溶液条件下，也不会与螺旋轴成角度。 这里我们 建议恢复我们的真空紫外线线性二向色性（LD）研究， 确定底部相对于螺旋线倾斜的角度 轴上的各种碱基序列和各种溶液条件。 在 一种基于螺旋核酸的流动LD实验， 有三个未知数：底座的倾斜度， 基座倾斜的轴线的系数，以及 聚合物在流动中的排列。 如果有一种以上的 如果核酸中的碱基的类型不同，则每种类型的碱基可以具有不同的互补性。 倾斜度和轴线。 我们的实验室开发了一种特殊的流动线性 二向色性仪器，将使测量到真空 紫外线区域，以便数据的信息内容 足以解决所有的未知数。 在以前的工作中， 确定一些简单脱氧多核苷酸的倾斜角，和 DNA本身。 我们现在将研究简单的核糖多核苷酸在水溶液中 溶液和简单的脱氧核糖核苷酸在溶液条件下， 生成A形式。 此外，我们建议准确地确定 A型DNA每圈的碱基对数量。 然后，我们将使用新的 基础倾角和螺旋线重复数据计算出相应的 真空紫外CD光谱 这些计算的光谱将被比较 与CD光谱测量到真空紫外区对我们的特殊 仪器仪表 此外，我们会比较质子间距离 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 NMR工作的NOESY数据获得的值。 采取 总的来说，这项工作对于确定真正的基础应该是有价值的。 溶液中多核苷酸和核酸的方向。

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.