摘要
在０～１℃的低温条件下叶绿体毫秒延迟发光的快相明显较室温时的高，说明低温条件有利于水氧化所释放的质子在类囊体膜上形成区域化；磷酸化能在毫秒级范围内就利用水氧化所产生的区域化质子合成ＡＴＰ，使毫秒延迟发光的快相降低。随着温度升高，水氧化产生的区域化质子易向非区域化质子转变，２５℃时毫秒延迟发光的快相主要与膜电位有关而难以观察到水氧化所释放的质子的影响。水氧化产生的质子区域化与叶绿体膜的状态密切相关。
The Effects of nigericin and vannomycin on the fast phase of millisecond delayed light emission (ms-DLE) inchloroplast and the stimulation of photophosphorylation (PSP ) by low concentrations of nigercin were investigatedat different temperatures. The relationship between ms-DLE and PSP was alsostudied at low and room temperatures.The fast phase of ms-DLE decreasedwith the increase of temperature in therange of 0-25 ℃, but only slightlyabove 8 ℃ (Fig. lA,B). At a low temperature of 0-1℃, the fast phase ofms-DLE was decreased significantly bynigericin (0. 5 umol/L) or valinomycin(0. 2 umol/L) and almost completelywhen both compounds were present(Fig. 2 ). The fast phase of ms-DLEwas not or only slightly affected by thesame concentration of nigericin, butwas almost completely demolished bythe same concentration of valinomycinat 25℃ (Fig. 3). The proceeding ofPSP decreased both the fast phase andslow phase of ms-DLE at 0 - 1℃,while the slow phase only at 25℃ (Fig.5 ). Furthermore, PSP was stimulatedby low concentrations of nigericin to alarger extent at 0-1℃ than at 25℃(Fig. 4 ). It is suggested that at lowertemperaturesthe protons from water oxidation are more likely to be localized onthe thylakoid membranes. PSP can utilize the localizd protons from water oxidation in the millisecond range, whichresults in a decrease of the fastphase ofms-DLE. The localized proton fromwater oxidation may shift to thebulkphase to be delocalized protons with anincrease of temperature, thereby thefast phase of ms-DLE is affected mainlyby the membrane electric potentials andthe effect of protons from water oxidation on the fast phase almost disapearsat 25 ℃ When the chloroplast preparation stored in liquid nitrogen was used,the difference between the ms-DLE atdifferent temperatures was not observedany more althrough the PSP activity remained the same as with fresh chloroplast preparation (Fig. 6 ). This fact indicates that whether the protons fromwater oxidation are localized on the thylakoid membrane is highly dependent onthe conditions of chloroplast membrane.
基金
国家自然科学基金
关键词
叶绿体
毫秒延迟发光
区域化质子
温度
chloroplast, millisecond delayed light emission, fast phase, photophosphorylation, localizedproton, nigericin, temperature
