光系统Ⅱ反应中心D_1-D_2-Cyt b_(559)的光破坏作用研究

PHOTODAMAGE OF PHOTOSYSTEM I REACTION CENTER D_1-D_2-CYTOCHROME B_558 COMPLEX

从高等植物叶绿体中分离得到的光系统Ⅱ(PSⅡ)反应中心D_1-D_2-Cytb(559)复合物很不稳定,极易受到光照的破坏。光照导致D_1-D_2-Cytb_(559)在红区(Qy带)的吸收光谱发生很大的变化,在最初光照45秒时间内,吸光度值升高,继续光照则吸光度值下降,而且680nm处的下降速度最大,吸收峰发生兰移,光照也导致荧光强度增大,发射峰兰移。所有这些结果表明,光破坏至少存在两个不同的过程,而且主要受到破坏的是原初电子供体P680。

Photosystem I reaction center D1-D2-Cytochrome b550 purified from high plant was damaged very easily by illumination. During initial 30S of light treatment, the absorbance increased. Following the process of absorbance increasing, continuing illumination led to the decrease of absorbance, blue-shifting of absorption maximum wavelength at red absorption region. Illumination also gave rise to increase of fluorescence emission intensity and blue-shifting of emission maximum wavelength. These results show that there may be two different processes of photodamaging to photosystem I reaction center and P680 is most sensitive to light treatment.