School of Life Sciences, Devi Ahilya University, Vigyan Bhawan, Indore, India.
J Bioenerg Biomembr. 2011 Apr;43(2):195-202. doi: 10.1007/s10863-011-9346-7. Epub 2011 Mar 4.
With an aim to improve our understanding of the mechanisms behind specific anion effects in biological membranes, we have studied the effects of sodium salts of anions of varying valency in thylakoid membranes. Rates of electron transport of PS II and PS I, 77K fluorescence emission and excitation spectra, cyclic electron flow around PS I and circular dichroism (CD) spectra were measured in thylakoid membranes in order to elucidate a general mechanism of action of inorganic anions on photosynthetic electron transport chain. Re-distribution of absorbed excitation energy has been observed as a signature effect of inorganic anions. In the presence of anions, such as nitrite, sulphate and phosphate, distribution of absorbed excitation energy was found to be more in favor of Photosystem I (PS I). The amount of energy distributed towards PS I depended on the valency of the anion. In this paper, we propose for the first time that energy re-distribution and its valence dependence may not be the effect of anions per se. The entry of negative charge (anion) is accompanied by influx of positive charge (protons) to maintain a balance of charge across the thylakoid membranes. As reflected by the CD spectra, the observed energy re-distribution could be a result of structural rearrangements of the protein complexes of PS II caused by changes in the ionic environment of the thylakoid lumen.
为了深入了解生物膜中特定阴离子作用的机制，我们研究了带不同价电荷的阴离子的钠盐对类囊体膜的影响。为了阐明无机阴离子对光合作用电子传递链的一般作用机制，我们测量了类囊体膜中 PS II 和 PS I 的电子传递速率、77K 荧光发射和激发光谱、PS I 周围的循环电子流和圆二色性（CD）光谱。我们观察到吸收激发能的再分布是无机阴离子的一个特征效应。在存在亚硝酸盐、硫酸盐和磷酸盐等阴离子的情况下，发现吸收激发能的分布更有利于光系统 I（PS I）。分配给 PS I 的能量的数量取决于阴离子的价数。在本文中，我们首次提出，能量再分布及其价依赖性可能不是阴离子本身的作用。负电荷（阴离子）的进入伴随着正电荷（质子）的流入，以保持类囊体膜两侧的电荷平衡。正如 CD 光谱所反映的那样，观察到的能量再分布可能是由于类囊体腔的离子环境变化导致 PS II 蛋白复合物的结构重排所致。
