沼泽红假单胞菌光合色素的分离、组成分析与光稳定性

Separation, characterization and light stability of photosynthetic pigments from Rhodopseudomonas palustris

摘要:

【目的】探求光对不产氧光合细菌类胡萝卜素(Car)和细菌叶绿素a (BChl a)稳定性的影响规律。【方法】以沼泽红假单胞菌CQV97为材料，采用硅胶柱层析和HPLC方法进行Car和BChl a组分的纯化和成分分析，采用吸收光谱法研究Car和BChl a组分的光稳定性。【结果】在Car和BChl a组分分离过程中，Car组分回收率高且稳定，而BChl a回收率波动性较大。Car组分中含有6种螺菌黄质系Car和极少量(<0.25%)的细菌脱镁叶绿素a。BChl a组分中包含BChl aGG、BChl aDHGG、BChl aTHGG和BChl aP 4种成分。Car和BChl a组分在黑暗条件下非常稳定。2 000 lx白炽灯、日光灯和自然光照射时，Car在70 min内非常稳定，但对紫外光敏感，半衰期为11.15 min，BChl a组分对白炽灯、日光灯、自然光和紫外灯的光降解速率常数(min–1)分别为0.169 8、0.028 9、0.213 9和0.026 4，半衰期(min)分别为4.47、29.68、4.20和26.19。【结论】一步硅胶柱层析可同时得到Car和BChl a纯组分。Car对白光相对稳定，对紫外光不稳定。BChl光稳定性很差，分离过程中短期见光是导致BChl a回收率波动性较大的原因，光降解过程中产生了相对稳定的中间产物。该研究结果为光合色素的精制、功能研究和应用提供了理论依据。

Abstract:

[Objective] To examine the effects of light on stability of carotenoids (Cars) and bacteriochlorophyll (BChl) a of anoxygenic phototrophic bacteria. [Methods] Using Rhodopesudomonas palustris CQV97 as a reference, we used silica gel column chromatography, HPLC and absorption spectrophotometry for the separation, composition analysis and light stability of Cars and BChl. [Results] The recovery of Cars was higher than that of BChl a whereas the recovery rate of BChl a showed light-dependent fluctuation. Six Cars and trace amount of bacteriopheophytin a (<0.25%) were detected in Car separation fraction. Four intermediates of BChl a including BChl aGG, BChl aDHGG, BChl aTHGG and BChl aP were detected in BChl a fraction, and BChl aP was predominated (76.73%). In the dark, both Cars and BChl a were very stable. Under different light irradiation of 2 000 lx, Cars kept stable within 70 minutes, but it was sensitive to UV radiation and its half-life was about 11.15 min. Under incandescent lamp, fluorescent lamp, natural light and UV radiation, the photodegradation rate constants (min–1) of BChl a were 0.169 8, 0.028 9, 0.213 9 and 0.026 4, corresponding half-lives were 4.47 min, 29.68 min, 4.20 min and 26.19 min, respectively. [Conclusion] BChl a and Cars could be seperated simultaneously by one-step gel column chromatography. Cars were stable toward light irradiation, but sensitive to UV radiation. BChl a was unstable toward light irradiation, the short-term light irradiation resulted in the fluctuation of BChl a recovery rate, a stable intermediate was found in the process of BChl a photolysis. The results will be helpful for refining and functional analyzing of the photosynthetic pigments of the anoxygenic phototrophic bacteria.