Miller C, Stahl N, Barrol M
Graduate Department of Biochemistry, Brandeis University, Waltham, Massachusetts 02254.
Neuron. 1988 Apr;1(2):159-64. doi: 10.1016/0896-6273(88)90200-0.
Ionic selectivity characteristics of the K+ channel from the sarcoplasmic reticulum were studied as a function of temperature in order to decompose the profile of Gibbs free energy along the conduction pore into its enthalpic and entropic components. For Li+, Na+, K+, and Rb+, the enthalpy of binding to the channel is close to zero. Activation enthalpies for transferring ions from bulk aqueous solution to the channel's selectivity region are 20-25 kJ/mol for Na+, K+, and Rb+ and substantially higher for Li+ and Cs+. Transfer of Li+ and Na+ to the selectivity region involved large favorable entropies. The results argue that the group IA cations shed about half their waters of hydration in permeating the selectivity region of this channel.
研究了肌浆网钾通道的离子选择性特征随温度的变化，以便将沿传导孔的吉布斯自由能分布分解为其焓和熵分量。对于锂离子、钠离子、钾离子和铷离子，与通道结合的焓接近零。钠离子、钾离子和铷离子从本体水溶液转移到通道选择性区域的活化焓为20 - 25千焦/摩尔，而锂离子和铯离子的活化焓则高得多。锂离子和钠离子转移到选择性区域涉及很大的有利熵。结果表明，第IA族阳离子在渗透该通道的选择性区域时大约脱去了一半的水化水。
