CYTOPLASMIC HYDROGEN-ION DIFFUSION-COEFFICIENT
CYTOPLASMIC HYDROGEN-ION DIFFUSION-COEFFICIENT
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DOI：
10.1016/s0006-3495(92)81953-7
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发表时间：
1992-06-01
影响因子：
3.4
通讯作者：
ABERCROMBIE, RF
中科院分区：
文献类型：
--
作者：
ALBALDAWI, NF;ABERCROMBIE, RF
用pH电极和从海洋无脊椎动物的巨大神经元中提取的细胞质样品测量表观细胞质质子扩散系数。通过突然改变样品一个表面的pH值并记录样品内pH值的弛豫，在pH值为6.0-7.2的酸性或中性范围内测得表观扩散系数为1.4 +/- 0.5 × 10（-6）cm 2/s（N = 7）。该值比移动的pH缓冲液的扩散系数（约8 × 10（-6）cm 2/s）低约5倍，比水合氢离子的扩散系数（93 × 10（-6）cm 2/s）低约68倍。移动的pH缓冲液（约为缓冲能力的15%）和非移动的缓冲液（约为缓冲能力的85%）可定量解释酸性或中性pH下的结果。在碱性pH（8.2-8.6）下，表观质子扩散系数增加至4.1 +/- 0.8 x 10（-6）cm 2/s（N = 7）。这种较大的扩散系数在碱性pH值可以定量解释的增强缓冲能力的移动的氨基酸。在这些实验的条件下，氢氧化物的移动不太可能影响表观氢离子扩散系数。
The apparent cytoplasmic proton diffusion coefficient was measured using pH electrodes and samples of cytoplasm extracted from the giant neuron of a marine invertebrate. By suddenly changing the pH at one surface of the sample and recording the relaxation of pH within the sample, an apparent diffusion coefficient of 1.4 +/- 0.5 x 10(-6) cm2/s (N = 7) was measured in the acidic or neutral range of pH (6.0-7.2). This value is approximately 5x lower than the diffusion coefficient of the mobile pH buffers (approximately 8 x 10(-6) cm2/s) and approximately 68x lower than the diffusion coefficient of the hydronium ion (93 X 10(-6) cm2/s). A mobile pH buffer (approximately 15% of the buffering power) and an immobile buffer (approximately 85% of the buffering power) could quantitatively account for the results at acidic or neutral pH. At alkaline pH (8.2-8.6), the apparent proton diffusion coefficient increased to 4.1 +/- 0.8 x 10(-6) cm2/s (N = 7). This larger diffusion coefficient at alkaline pH could be explained quantiatively by the enhanced buffering power of the mobile amino acids. Under the conditions of these experiments, it is unlikely that hydroxide movement influences the apparent hydrogen ion diffusion coefficient.