title: The binding properties of photosensitizer methylene blue to herring sperm DNA: a spectroscopic study.
abstract: Methylene blue (MB) is a phenothiazinium photosensitizer with promising applications in the photodynamic therapy (PDT) for anticancer treatment. The binding properties of MB to herring sperm DNA have been investigated by the measurements of absorption spectra, quenching experiments and the elucidation of the photobleaching processes. Remarkable hypochromic and bathochromic effects of MB in the presence of increasing amounts of DNA have been observed in the absorption spectra. The quenching of MB by the DNA bases obeys the Stern-Volmer equation and ferrocyanide quenching of MB in the absence and presence of DNA is also measured as extended experiments. Results from the above spectral measurements are all consistent with the intercalative binding mode of MB to DNA with the Kb value of 1.89 x 10(4) M(-1). The photobleaching processes of MB and its DNA complex have also been studies, which indicate that the photobleaching of MB and its DNA complex proceeds with different mechanisms and the reactive oxygen species are responsible for the self-sensitized photooxidation of MB.
authors.affiliation: Institute of Modern Optics, Nankai University, Tianjin 300071, PR China. leiz@caltech.edu
authors.forename: Lei Z
authors.initials: LZ
authors.lastname: Zhang
authors.forename: Guo-Qing
authors.initials: GQ
authors.lastname: Tang
mesh_terms: D000818:Animals; D004247:DNA / Q000737:chemistry* / Q000378:metabolism; D005295:Ferrocyanides / Q000737:chemistry; D005399:Fishes / Q000378:metabolism*; D008297:Male; D008751:Methylene Blue / Q000737:chemistry* / Q000378:metabolism; D015394:Molecular Structure; D038761:Photobleaching / Q000528:radiation effects; D017319:Photosensitizing Agents / Q000737:chemistry* / Q000378:metabolism; D013057:Spectrum Analysis; D013094:Spermatozoa / Q000378:metabolism* / Q000528:radiation effects
chemical_list: D005295:Ferrocyanides; D017319:Photosensitizing Agents; D004247:DNA; C020354:hexacyanoferrate II; D008751:Methylene Blue