Robertson B, Lukashev E P
Biotechnology Division, National Institute of Standards and Technology, Gaithersburg, Maryland, USA.
Biophys J. 1995 Apr;68(4):1507-17. doi: 10.1016/S0006-3495(95)80323-1.
The photocurrent transient generated by bacteriorhodopsin (bR) on a tin-oxide electrode is due to pH change and not to charge displacement as previously assumed. Films of either randomly oriented or highly oriented purple membranes were deposited on transparent electrodes made of tin-oxide-coated glass. The membranes contained either wild-type or D96N-mutant bR. When excited with yellow light through the glass, the bR pumps protons across the membrane. The result is a rapid local pH change as well as a charge displacement. Experiments with these films show that it is the pH change rather than the displacement that produces the current transient. The calibration for the transient pH measurement is given. The sensitivity of a tin-oxide electrode to a transient pH change is very much larger than its sensitivity to a steady-state pH change.
细菌视紫红质（bR）在氧化锡电极上产生的光电流瞬变是由于pH值变化，而非如先前假设的电荷位移。随机取向或高度取向的紫膜薄膜被沉积在由氧化锡涂层玻璃制成的透明电极上。这些膜包含野生型或D96N突变体bR。当通过玻璃用黄光激发时，bR将质子泵过膜。结果是快速的局部pH值变化以及电荷位移。对这些薄膜进行的实验表明，产生电流瞬变的是pH值变化而非位移。给出了瞬态pH测量的校准。氧化锡电极对瞬态pH变化的灵敏度远大于其对稳态pH变化的灵敏度。
