Photosynthesis Research Unit, U.S. Department of Agriculture, Agricultural Research Service, Urbana, Illinois 61801.
Plant Physiol. 1991 Feb;95(2):522-8. doi: 10.1104/pp.95.2.522.
Effective ionophore:chlorophyll ratios were determined for various ionophores that decrease the electrical potential across thylakoid membranes in intact and hypo-osmotically lysed chloroplasts isolated from spinach (Spinacia oleracea). The efficacy of gramicidin D, valinomycin, carbonylcyanide m-chlorophenylhydrazone, and dicyclohexano-18-crown-6 in collapsing the electrical potential was determined spectrophotometrically by the decay half-time of the absorbance change at 518 nanometers induced by a saturating, single turnover flash. The results show that the effectiveness of the ionophores in collapsing the electrical potential in intact and lysed chloroplasts depends on the amount of ionophore-accessible membrane in the assay medium. Only gramicidin exhibited a significant difference in efficacy between intact and lysed chloroplasts. The ratio of gramicidin to chlorophyll required to collapse the electrical potential was more than 50 times higher in intact chloroplasts than in lysed chloroplasts. The efficacy of carbonylcyanide m-chlorophenylhydrazone was significantly reduced in the presence of bovine serum albumin. The other ionophores tested maintained their potency in the presence of bovine serum albumin. Valinomycin was the most effective ionophore tested for collapsing the electrical potential in intact chloroplasts, whereas gramicidin was the most potent ionophore in lysed chloroplasts. The significance of the ionophore:chlorophyll ratios required to collapse the electrical potential is discussed with regard to bioenergetic studies, especially those that examine the contribution of the transmembrane electrochemical potential to protein transport into chloroplasts.
叶绿素的比例确定了各种离子载体，这些载体降低了完整的和经低渗裂解的菠菜（Spinacia oleracea）叶绿体中类囊体膜的跨膜电势。通过饱和单周转闪光诱导的 518 纳米处吸光度变化的半衰期来分光光度法测定了短杆菌肽 D、缬氨霉素、羰基氰化物 m-氯代苯腙和二环己基-18-冠-6 使电势崩溃的功效。结果表明，离子载体在完整和裂解叶绿体中使电势崩溃的效果取决于测定介质中离子载体可接近的膜的量。只有短杆菌肽在完整和裂解叶绿体之间的功效上表现出显著差异。在完整叶绿体中，使电势崩溃所需的短杆菌肽与叶绿素的比例比在裂解叶绿体中高 50 多倍。在牛血清白蛋白存在下，羰基氰化物 m-氯代苯腙的功效显著降低。测试的其他离子载体在牛血清白蛋白存在下保持其效力。缬氨霉素是测试的最有效的离子载体，用于使完整叶绿体中的电势崩溃，而短杆菌肽是裂解叶绿体中最有效的离子载体。使电势崩溃所需的离子载体：叶绿素的比例对于生物能量学研究具有重要意义，特别是那些研究跨膜电化学电势对叶绿体中蛋白质转运的贡献的研究。
