Larsen R W, Jasuja R, Hetzler R K, Muraoka P T, Andrada V G, Jameson D M
Department of Chemistry, University of Hawaii at Manoa, Honolulu 96822, USA.
Biophys J. 1996 Jan;70(1):443-52. doi: 10.1016/S0006-3495(96)79587-5.
Recent studies have demonstrated that caffeine can act as an antimutagen and inhibit the cytoxic and/or cytostatic effects of some DNA intercalating agents. It has been suggested that this inhibitory effect may be due to complexation of the DNA intercalator with caffeine. In this study we employ optical absorption, fluorescence, and molecular modeling techniques to probe specific interactions between caffeine and various DNA intercalators. Optical absorption and steady-state fluorescence data demonstrate complexation between caffeine and the planar DNA intercalator acridine orange. The association constant of this complex is determined to be 258.4 +/- 5.1 M-1. In contrast, solutions containing caffeine and the nonplanar DNA intercalator ethidium bromide show optical shifts and steady-state fluorescence spectra indicative of a weaker complex with an association constant of 84.5 +/- 3.5 M-1. Time-resolved fluorescence data indicate that complex formation between caffeine and acridine orange or ethidium bromide results in singlet-state lifetime increases consistent with the observed increase in the steady-state fluorescence yield. In addition, dynamic polarization data indicate that these complexes form with a 1:1 stoichiometry. Molecular modeling studies are also included to examine structural factors that may influence complexation.
最近的研究表明，咖啡因可作为一种抗诱变剂，并抑制某些DNA嵌入剂的细胞毒性和/或细胞生长抑制作用。有人提出，这种抑制作用可能是由于DNA嵌入剂与咖啡因形成了复合物。在本研究中，我们采用光吸收、荧光和分子建模技术来探究咖啡因与各种DNA嵌入剂之间的特定相互作用。光吸收和稳态荧光数据表明咖啡因与平面DNA嵌入剂吖啶橙之间形成了复合物。该复合物的缔合常数确定为258.4±5.1 M-1。相比之下，含有咖啡因和非平面DNA嵌入剂溴化乙锭的溶液显示出光位移和稳态荧光光谱，表明形成了缔合常数为84.5±3.5 M-1的较弱复合物。时间分辨荧光数据表明，咖啡因与吖啶橙或溴化乙锭之间形成复合物会导致单重态寿命增加，这与观察到的稳态荧光产率增加一致。此外，动态极化数据表明这些复合物以1:1的化学计量比形成。还包括分子建模研究，以检查可能影响络合作用的结构因素。
