A Velocity-Gradient Flow Cell for Raman and Emission Spectroscopy of a DNA-Drug Solution

本工作的目的是建立一种新的仪器，用它可以检测溶液中DNA-药物复合物的几何形状。因此，在对这样的溶液进行光谱测量时，有关所讨论的分子的各向异性性质的信息是模糊的。因此，理想的是使分子在溶液中取向。对于DNA双链体来说，将其溶液置于速度梯度为10^3 cm s^ /cm数量级的流体中是可能<-1>的。Wada和Kozawa（J.Polymer Sci.，例如，A2，853（1964））在置于两个同轴圆筒之间的差距中的溶液流中产生了这样的速度梯度，其中一个圆筒快速旋转。他们研究了DNA在260 nm吸收的各向异性。在本研究中，将类似的技术应用于拉曼和荧光光谱。将DNA溶液置于两个同轴圆柱体之间差距（1 mm）中;外圆筒的内径为12 mm，内筒的外径为10 mm。当内筒以每分钟2500转旋转时，穿过差距产生足够大的液流速度梯度，使得DNA分子沿着流动方向取向。DNA分子的拉曼散射的各向异性是通过将激发激光束从圆柱体的底部沿平行于圆柱体轴的方向通入差距来检查的。将抗癌药物阿克拉霉素A（盐酸盐）加入到DNA溶液中，并检查其发射光谱和拉曼光谱的各向异性。阿克拉霉素与DNA的结合是以其发色团平行于DNA双链体的基面的方式进行的，因此，新构建的仪器被证明是阐明DNA-药物相互作用的几何结构的有力工具。

The purpose of this work is to construct a new instrument with which one can examine the geometry of a DNA-Drug complex in a solution.In ordinary solutions, the molecules are randomly oriented. In a spectroscopic measurement on such a solution, therefore, information on the anisotropic properties of the molecules in question is obscured. Thus it is desirable to have molecules oriented in solution. This is known to be possible for the DNA duplex by placing its solution in a flow with a velocity gradient of 10^3 cm s^<-1>/cm order of magnitude. Wada and Kozawa (J.Polymer Sci.,A2, 853 (1964)), for example, produced such a velocity gradient in the flow of solution placed in the gap between two coaxial cylinders, one of which was rapidly rotated. They examined the anisotropy of the 260 nm absorption of DNA In the present study, a similar technique has been applied to Raman and fluorescence spectroscopy.A DNA solution was placed in the gap (1 mm) between two coaxial cylinders; the inside diameter of the outer cylinder was 12 mm, and the outside diameter of the inner cylinder was 10 mm. When the inside cylinder was rotated at 2500 revolutions per minute, a sufficiently large velocity gradient of the liquid flow was produced across the gap so that the DNA molecules were oriented along the flow direction. Anisotropy of the Raman scatterings of the DNA molecule was examined by passing an exciting laser beam into the gap from the bottom of the cylinder in the direction parallel to the cylinder axis. An antitumor drug, aclacinomycin A (HCl salt), was added to the DNA solution, and the anisotropy of its emission and Raman spectra was also examined. It has been established that aclacinomycin binds to DNA with its chromophore oriented parallel to the base plane of the DNA duplex.Thus, the newly constructed instrument proved to be powerful for elucidating the geometry of a DNA-drug interaction.