Passechnik V I, Hianik T
Scientific Research Center ELDIS, Institute of Radioengineering and Electronics, Russian Academy of Sciences, Moscow, Russia.
Gen Physiol Biophys. 1998 Mar;17(1):51-69.
A new, sensitive method of measurement of current-voltage characteristics (CVC) of the type i(U) approximately U(1 + beta U2) was applied to study ionic channels formed by gramicidin D in bilayer lipid membranes (BLM). The values of the non-linearity coefficient beta of the CVC of membranes modified by gramicidin D depended on electrolyte concentration, C, and expressed the weak nonlinearity of the CVC. In symmetric electrolyte conditions, the coefficient beta(A) increased with the increasing electrolyte concentration from -17 V-2 at 0.03 mol/l KCl to 8 V-2 at 3 mol/l KCl. In asymmetric electrolyte conditions (different electrolyte concentrations at the two sides of the BLM) the coefficient beta(A) also increased with increasing C. A theory is proposed describing the weak nonlinearity of CVC of ionic channels based on electrodiffusion model. This theory assumes that the electrochemical potential mu(x) of an ion within the ion channel depends on the coordinate x along the channel axis. According to the proposed model, CVC nonlinearity is mainly determined by the ends of the ion channel. We showed that the structure of gramicidin D ionic channel is sensitive to the concentration of ions, and in fact changes at one end of the channel influence the parameters of the other channel end.
一种新的、灵敏的测量电流 - 电压特性（CVC）的方法，即i(U)≈U(1 + βU²) 类型，被应用于研究短杆菌肽D在双层脂质膜（BLM）中形成的离子通道。由短杆菌肽D修饰的膜的CVC的非线性系数β值取决于电解质浓度C，并表现出CVC的弱非线性。在对称电解质条件下，系数β(A) 随着电解质浓度的增加而增加，从0.03 mol/l KCl时的 - 17 V⁻² 增加到3 mol/l KCl时的8 V⁻²。在非对称电解质条件下（BLM两侧的电解质浓度不同），系数β(A) 也随着C的增加而增加。提出了一种基于电扩散模型描述离子通道CVC弱非线性的理论。该理论假设离子通道内离子的电化学势μ(x) 取决于沿通道轴的坐标x。根据所提出的模型，CVC非线性主要由离子通道的末端决定。我们表明，短杆菌肽D离子通道的结构对离子浓度敏感，实际上通道一端的变化会影响另一端的参数。
