Allen M T, Lynch M, Lagos A, Redmond R W, Kochevar I E
Wellman Laboratories of Photomedicine, Massachusetts General Hospital, Boston 02114.
Biochim Biophys Acta. 1991 Sep 2;1075(1):42-9. doi: 10.1016/0304-4165(91)90072-o.
A 2-fold enhancement in the efficiency of rose bengal-photosensitized inhibition of red cell acetylcholinesterase activity was observed upon excitation of the dye in the ultraviolet (UV) (313 nm) compared to irradiation in the visible (514 or 550 nm). The measurements of efficiency of photosensitized enzyme inhibition were based on the effect produced when the same number of photons are absorbed by rose bengal (RB) at each wavelength. The mechanism for this unexpected enhancement of RB photosensitization upon UV excitation was investigated. The yield of singlet oxygen (O2(1 delta g], detected by time-resolved luminescence at 1270 nm, was independent of excitation wavelength for RB. Radicals were produced upon irradiation of RB at 313 nm but not at 514 nm as detected by bleaching of N,N-dimethylnitrosoaniline (RNO). Irradiation of RB at 313 nm but not at 514 nm appeared to cause homolytic cleavage of carbon-iodine bonds in the dye because iodine radicals, I, detected as I2 were produced with a quantum yield of 0.0041 +/- 0.0005 upon excitation in the UV. Photolysis of I2 in the presence of RNO caused bleaching of the RNO absorption at 440 nm, apparently resulting from reaction of I with RNO. Thus, the enhanced photosensitization upon UV excitation of RB is attributed to formation of I and/or RB. These results indicate that radicals, produced with low relative yield but having high reactivity compared to O2(1 delta g), can contribute to photosensitized enzyme inhibition and may represent an alternative mechanism for photodynamic therapy.
与在可见光（514或550nm）照射相比，当在紫外线（UV）（313nm）激发孟加拉玫瑰红时，观察到其对红细胞乙酰胆碱酯酶活性的光致敏抑制效率提高了2倍。光致敏酶抑制效率的测量基于在每个波长下相同数量的光子被孟加拉玫瑰红（RB）吸收时产生的效应。研究了这种紫外线激发时RB光致敏意外增强的机制。通过1270nm的时间分辨发光检测到的单线态氧（O2(1Δg]）产率与RB的激发波长无关。如通过N，N-二甲基亚硝基苯胺（RNO）的漂白所检测到的，在313nm照射RB时会产生自由基，但在514nm照射时不会产生。在313nm而不是514nm照射RB似乎会导致染料中碳-碘键的均裂，因为在紫外线激发下产生的碘自由基I以I2形式被检测到，量子产率为0.0041±0.0005。在RNO存在下I2的光解导致RNO在440nm处的吸收漂白，这显然是由于I与RNO的反应。因此，RB紫外线激发时光致敏增强归因于I和/或RB的形成。这些结果表明，自由基虽然相对产率低，但与O2(1Δg)相比具有高反应性，可有助于光致敏酶抑制，并且可能代表光动力疗法的另一种机制。
