多色蓝在核酸分子上的Langmuir聚集吸附

Langmuir Aggregation of Polychrome Blue on Nucleic Acids

用微相吸附-光谱修正（MPASC）新技术研究核酸与多色蓝（PCB）探针分子间的相互作用,分析核酸分子内双静电膜的形成与 Langmuir吸附的关联性.通过pH 7.24的介质核酸-PCB反应的光谱研究,测定了结合产物的物理化学参数:结合比IPCB:2DNA-PCB、IPCB:3RNA-PCB,平衡常数KDNA-PCB=5.42 X 104,KRNA-PCB=2.82 x 104,摩尔吸收系数ε（DNA-PCB,625nm）=5.65x103（mol-1·L）·cm-1,ε（RNA-PCB,625nm）=3.85x103（mol-1·L）·cm-1结果表明,RNA分子仅形成约60％双螺旋结构链,核酸双螺旋每一周期的负静电沟最大聚集10个PCB分子.该吸附反应用于核酸样品测定,结果良好.

In the present work, the combination of both the Langmuir adsorption and the spectral correction (MPASC) technique are described. It provides a very helpful experimental method for the study of aggregation of a dye on biomacromolecules. The helix, winding and folding of DNA form double electrostatic films and their surface will selectively attract charged organic compounds in only monolayer untill kinetic equilibrium approached. The physico-chemical constants such as equilibrium constant and binding stoichiometry of the aggregate may be determined. The adsorption of polychrome blue(PCB) on nucleic acids has been investigated at pH 7. 24 and it obeys Langmuir monolayer adsorption. Results showed that the adsorption ratio of PCB to DNA-PCB is 0. 5 : 1 and that to RNA-PCB 0. 3 : 1, their adsorption constants are KDNA-PCB =5. 42 ×104 and KRNA-PCB = 2. 82× 104(30℃) respectively, and their real adsorptivity s (DNA-PCB, 625 nm) = 5. 65×103 and E(RNA-PCB, 625 nm) =3. 85×103 (mol-1.L) .cm-1. By varying the operation condition, we observed that the adsorption ratio of PCB to DNA decreased with increasing ionic strength and temperature. This indicats that the interaction is an adsorption but not a complexation. This interaction was applied to the quantitative determination of DNA. In the presence of EDTA, many ions or compounds such as protein, alkali earths, Mn(II), Cu(Ⅱ), Fe(Ⅱ), Zn (Ⅱ), Pb(Ⅱ), Ni(Ⅱ), Co(Ⅱ) and Cd(Ⅱ) have no interference to the direct determination of nucleic acids.