Lomax T L, Mehlhorn R J, Briggs W R
Proc Natl Acad Sci U S A. 1985 Oct;82(19):6541-5. doi: 10.1073/pnas.82.19.6541.
Closed and pH-tight membrane vesicles prepared from hypocotyls of 5-day-old dark-grown seedlings of Cucurbita pepo accumulate the plant growth hormone indole-3-acetic acid along an imposed proton gradient (pH low outside, high inside). The use of electron paramagnetic spin probes permitted quantitation both of apparent vesicle volume and magnitude of the pH gradient. Under the experimental conditions used, hormone accumulation was at minimum 20-fold, a value 4 times larger than what one would predict if accumulation reflected only diffusional equilibrium at the measured pH gradient. It is concluded that hormone uptake is an active process, with each protonated molecule of hormone accompanied by an additional proton. Experiments with ionophores confirm that it is the pH gradient itself which drives the uptake.
从5日龄黑暗中生长的西葫芦幼苗下胚轴制备的封闭且pH值紧密的膜囊泡，沿着施加的质子梯度（外部pH低，内部pH高）积累植物生长激素吲哚-3-乙酸。使用电子顺磁共振自旋探针可以对表观囊泡体积和pH梯度大小进行定量。在所使用的实验条件下，激素积累至少为20倍，该值比如果积累仅反映在测量的pH梯度下的扩散平衡所预测的值大4倍。得出的结论是，激素摄取是一个主动过程，每个质子化的激素分子伴随着一个额外的质子。离子载体实验证实，正是pH梯度本身驱动了摄取。
