Molecular recognition of DNA by small molecules: AT base pair specific intercalative binding of cytotoxic plant alkaloid palmatine
Molecular recognition of DNA by small molecules: AT base pair specific intercalative binding of cytotoxic plant alkaloid palmatine
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DOI：
10.1016/j.bbagen.2007.03.001
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发表时间：
2007-07-01
影响因子：
3
通讯作者：
Kumar, Gopinatha Suresh
中科院分区：
文献类型：
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作者：
Bhadra, Kakah;Maiti, Motilal;Kumar, Gopinatha Suresh
用竞争透析法、分光光度法、荧光光谱法、热熔融法、圆二色性法、粘度法和等温滴定量热法研究了细胞毒性生物碱巴马汀（palmatine）与四种人工合成多核苷酸（poly（dA）、poly（dT）、poly（dA-dT）、poly（dA-dT）、poly（dG）、poly（dC）和poly（dG-dC）、poly（dG-dC））的碱基依赖性结合。生物碱与各种多核苷酸的结合依赖于碱基对的序列。根据邻位排阻模型测定的吸光度数据表明，内在结合常数的顺序为poly（dA）.poly（dT）> poly（dA-dT）.poly（dA-dT）> poly（dG-dC）.poly（dG-dC）> poly（dG）.poly（dC）。竞争透析、稳态荧光强度的增加、荧光量子产率的增加、对热变性的稳定性和圆二色性光谱中的扰动也揭示了这种亲和力。在多核苷酸中，poly（dA）·poly（dT）在结合值低于r = 0.05时显示正协同性。粘度的研究表明，在强结合区，DNA的轮廓长度的增加强烈依赖于AT聚合物的碱基对序列较高，并诱导共价闭合的超螺旋DNA的解旋-重旋过程。等温滴定量热数据表明，一个单一的熵驱动的结合事件在AT均聚物，而与杂聚合物涉及两种结合模式，熵驱动的强结合，然后由焓驱动的弱结合。这些结果明确地确立了生物碱巴马汀通过插层机制与AT均聚物和杂聚物强烈结合。(c)2007 Elsevier B. V.保留所有权利。
The base dependent binding of the cytotoxic alkaloid palmatine to four synthetic polynucleotides, poly(dA).poly(dT), poly(dA-dT).poly (dA-dT), poly(dG).poly(dC) and poly(dG-dC).poly(dG-dC) was examined by competition dialysis, spectrophotometric, spectrofluorimetric, thermal melting, circular dichroic, viscometric and isothermal titration calorimetric (ITC) studies. Binding of the alkaloid to various polynucleotides was dependent upon sequences of base pairs. Binding data obtained from absorbance measurements according to neighbour exclusion model indicated that the intrinsic binding constants decreased in the order poly(dA).poly(dT) > poly(dA-dT).poly(dA-dT) > poly(dG-dC).poly(dG-dC) > poly(dG).poly(dC). This affinity was also revealed by the competition dialysis, increase of steady state fluorescence intensity, increase in fluorescence quantum yield, stabilization against thermal denaturation and perturbations in circular dichroic spectrum. Among the polynucleotides, poly(dA).poly(dT) showed positive cooperativity, at binding values lower than r = 0.05. Viscosity studies revealed that in the strong binding region, the increase of contour length of DNA depended strongly on the sequence of base pairs being higher for AT polymers and induction of unwinding-rewinding process of covalently closed superhelical DNA. Isothermal titration calorimetric data showed a single entropy driven binding event in the AT homo polymer while that with the hetero polymer involved two binding modes, an entropy driven strong binding followed by an enthalpy driven weak binding. These results unequivocally established that the alkaloid palmatine binds strongly to AT homo and hetero polymers by mechanism of intercalation. (c) 2007 Elsevier B.V. All rights reserved.