竹红菌甲素敏化嘌呤和嘧啶碱的光氧化作用及其影响因素

本工作利用光吸收和高效液相色谱(HPLC)技术研究了甲素对DNA分子中四种碱基A、G、C和T光氧化的敏化作用,发现在反应体系的pH为9.0、甲素浓度为3×10~(-5)mol/L、光照40分钟时,G和T紫外吸收明显降低;HPLC分析发现甲素敏化的G光氧化体系比对照体系多出现一组分峰(滞留时间0.927分钟),该峰用475nm波长检测比260nm波长检测灵敏。根据反应机制推测是G环破裂产物。在反应条件固定时,甲素敏化G的光氧化作用受pH、光照时间及甲素浓度影响极大。单线态氧淬灭剂——叠氮钠浓度在40—110mmol/L可部分抑制甲素敏化G的光氧化作用,>110mmol/L时反应完全被阻断,提示甲素对G光氧化的敏化作用主要通过单线态氧(~1O_2)即Ⅱ型机制起作用。本文还讨论了G光氧化的可能途径。

Factors Effect the Photooxidation of Purine and Pyrimidine Bases Sensitized by Hypocrellin A

Studies of Hypocrellin A-sensitized photooxidation of purine and pyrimidine bases exist in DNA molecules were carried out using optical absorption spectrum and HPLC techiques. It was found that ultraviolet absorbance of guanine and thymine systems with Hypocrellin A concentration of 3×10-5mol/L and pH 9.0 decresed significantly after visible light irradiation for 40 minutes. A new peak occured in reverse-phase HPLC elution profile of guanine photooxidation sensitized by Hypocrellin A.The new peak coud be more sensitively detected at 475nm tnan at 260nm. It was proposed that the product(s) formed from Hypocrellin Asensitized photooxidation of guanine might be cleavage product(s) of the purine ring.under tne given condition, the rate of Hypocrellin A-sensitized photooxidation of guanine was dependent on pH, illumination time and sensitizer concentration. Azide anion, the specific quencher for 1O2, could inhibit the photooxidation of guanine partly at a concentration of 40 mmol/L and completely at concentrations higher than 110 mmol/L.These results showed that 1O2 mechanism was involved in Hyprcrellin A-sensitized photooxidation of guanine. The possible photooxidation pathway of Guanine was disccused.