Henze R, Neher E, Trapane T L, Urry D W
J Membr Biol. 1982;64(3):233-9. doi: 10.1007/BF01870890.
Dielectric permitivities have been determined for suspensions of lysolecithin packaged malonyl gramicidin channels over the frequency range of 5 kHz to 900 MHz and under conditions of approximately equimolar concentrations (approximately 10mM) of channels and salts. The salts were lithium chloride, sodium chloride and thallium acetate. A relaxation process unique to the thallium acetate-channel system was observed which on analysis gave rise to a relaxation time at 25 degrees of 120 msec. The permitivity data, as well as a comparison of binding constants, indicate that the relaxation process results from TI+ being bound within the channel and more specifically from an intrachannel ion translocation with a rate constant of approximately 4 x 10(6) sec-1 and with an energy of activation of less than 6.7 kcal/mole. These data compare favorably with data from conductance studies on planar bilayers and with ion and carbon-13 nuclear magnetic studies on the lysolecithin packaged malonyl gramicidin channels which combine to indicate that the relaxation process is due to the jump of the thallium ion across a central barrier.
已测定了溶血卵磷脂包裹的丙二酰短杆菌肽通道悬浮液在5千赫至900兆赫频率范围内，以及在通道和盐的浓度约为等摩尔（约10毫摩尔）的条件下的介电常数。所用的盐为氯化锂、氯化钠和醋酸铊。观察到醋酸铊 - 通道系统特有的一个弛豫过程，经分析在25摄氏度时产生了120毫秒的弛豫时间。介电常数数据以及结合常数的比较表明，弛豫过程是由于铊离子（Tl⁺）结合在通道内，更具体地说是由于通道内离子的转运，其速率常数约为4×10⁶秒⁻¹，活化能小于6.7千卡/摩尔。这些数据与平面双层膜电导研究的数据以及对溶血卵磷脂包裹的丙二酰短杆菌肽通道的离子和碳 - 13核磁共振研究的数据相比很有利，这些研究共同表明弛豫过程是由于铊离子跨越中心屏障的跳跃。
