Castaing M, Kraus J L, Beaufils P, Ricard J
Centre de Biochimie et de Biologie Moleculaire, CBM2/CNRS 31, Marseille, France.
Biophys Chem. 1991 Nov;41(2):203-15. doi: 10.1016/0301-4622(91)80020-r.
The kinetics of Na+ transport by (221)C10-cryptand through thin lipid membranes were determined by performing temperature-jump relaxation experiments on large unilamellar vesicles (L.U.V.) loaded with a fluorescent pH indicator. Applying temperature jumps of 4 to 7 degrees C to liposomes having phosphate as internal buffer and Tris as external buffer resulted in transmembrane delta pH's of about 0.104 to 0.182. After a temperature-jump, a decay in the delta pH was observed which corresponded to a Na+/H+ exchange occurring through membranes in the simultaneous presence of the cryptand and a proton carrier. The transport of Na+ ions by (221)C10 was found to be a fast kinetic process. Its initial rate increased with both the temperature and the cryptand concentrations. In addition, the temperature-induced changes in the apparent rate constants of the translocation of Na+ by (221)C10 were carrier concentration-dependent, and the apparent activation energy required to activate the transport decreased significantly with increasing cryptand concentrations. The results are discussed in terms of the structural, physico-chemical and electrical characteristics of carriers and complexes.
通过对负载荧光pH指示剂的大单层囊泡（L.U.V.）进行温度跳跃弛豫实验，测定了(221)C10-穴醚通过薄脂质膜转运Na⁺的动力学。对以磷酸盐为内部缓冲液、Tris为外部缓冲液的脂质体施加4至7摄氏度的温度跳跃，导致跨膜ΔpH约为0.104至0.182。温度跳跃后，观察到ΔpH的衰减，这对应于在穴醚和质子载体同时存在的情况下通过膜发生的Na⁺/H⁺交换。发现(221)C10对Na⁺离子的转运是一个快速动力学过程。其初始速率随温度和穴醚浓度的增加而增加。此外，温度诱导的(221)C10转运Na⁺的表观速率常数的变化与载体浓度有关，并且激活转运所需的表观活化能随着穴醚浓度的增加而显著降低。根据载体和配合物的结构、物理化学和电学特性对结果进行了讨论。
