Pilch D S, Waring M J, Sun J S, Rougée M, Nguyen C H, Bisagni E, Garestier T, Hélène C
Laboratoire de Biophysique, Muséum National d'Histoire Naturelle INSERM U 201, CNRS, UA 481, Paris, France.
J Mol Biol. 1993 Aug 5;232(3):926-46. doi: 10.1006/jmbi.1993.1440.
A benzo[e]pyridoindole derivative, 3-methoxy-7H-8-methyl-11-[(3'-amino)propylamino] -benzo[e]pyrido[4,3-b]indole (BePI), and its interactions with double and triple-helical DNA have been investigated by a variety of fluorescence, spectrophotometric, hydrodynamic and molecular modeling techniques. Binding to DNA stabilizes the doubly charged (+2) form of BePI, increasing the apparent pKa of the 10-NH proton by approximately 1 pH unit. Binding to DNA also quenches the fluorescence of BePI, with a greater extent of quenching upon binding triplex relative to duplex DNA. BePI preferentially binds (and stabilizes) triple-helical relative to double-helical DNA. This preferential binding is not restricted to triplexes containing solely T x A.T base triplets. In addition, BePI preferentially stabilizes the poly(dA).poly(dT) relative to the poly[d(A-T)].poly[d(A-T)] duplex. Viscosity studies demonstrate that, upon binding, BePI induces the unwinding of negative supercoils in the pBR322 plasmid, and increases the relative contour lengths of double and triple-helical polydeoxynucleotides. Fluorescence studies reveal that energy transfer occurs from polynucleotide bases to bound BePI molecules in both BePI/duplex and BePI/triplex complexes. In a BePI/triplex complex, an average of 4.8 bases appear to transfer excitation energy totally to a bound BePI molecule, while in various BePI/duplex complexes an average of only 2.5 bases appear to do so, indicating that energy transfer is more efficient in the former complex. Measurements of fluorescence quenching indicate that BePI is protected from quenching by acrylamide when bound to either double or triple-helical polynucleotides. The viscosity and fluorescence behavior of BePI are fully consistent with the conclusion that BePI intercalates into both double and triple-helical DNA. Molecular modeling studies suggest that stronger stacking interactions between intercalated BePI and adjacent bases in BePI/triplex relative to BePI/duplex complexes may account for the enhanced thermal stability of the former complex.
一种苯并[e]吡啶吲哚衍生物，3-甲氧基-7H-8-甲基-11-[(3'-氨基)丙基氨基]-苯并[e]吡啶[4,3-b]吲哚（BePI），以及它与双链和三链螺旋DNA的相互作用，已经通过多种荧光、分光光度、流体动力学和分子建模技术进行了研究。与DNA结合会使BePI的双电荷（+2）形式稳定下来，使10-NH质子的表观pKa增加约1个pH单位。与DNA结合还会淬灭BePI的荧光，与双链DNA结合相比，与三链DNA结合时淬灭程度更大。相对于双链螺旋DNA，BePI优先结合（并稳定）三链螺旋DNA。这种优先结合并不局限于仅含有T x A.T碱基三联体的三链体。此外，相对于聚[d(A-T)].聚[d(A-T)]双链体，BePI优先稳定聚（dA）.聚（dT）。粘度研究表明，结合时BePI会诱导pBR322质粒中的负超螺旋解旋，并增加双链和三链螺旋多脱氧核苷酸的相对轮廓长度。荧光研究表明，在BePI/双链体和BePI/三链体复合物中，能量都会从多核苷酸碱基转移到结合的BePI分子上。在BePI/三链体复合物中，平均有4.8个碱基似乎将激发能量完全转移到一个结合的BePI分子上，而在各种BePI/双链体复合物中，平均只有2.5个碱基似乎会这样做，这表明能量转移在前者复合物中更有效。荧光淬灭测量表明，当BePI与双链或三链螺旋多核苷酸结合时，它受到丙烯酰胺淬灭的保护。BePI的粘度和荧光行为完全符合BePI插入双链和三链螺旋DNA的结论。分子建模研究表明，相对于BePI/双链体复合物，插入的BePI与BePI/三链体复合物中相邻碱基之间更强的堆积相互作用可能解释了前者复合物热稳定性增强的原因。
