Shi Y L, Edwards C, Lazarovici P
Shanghai Institute of Physiology, Chinese Academy of Sciences.
Nat Toxins. 1995;3(3):151-5. doi: 10.1002/nt.2620030306.
Using the method of bilayer membranes at the tip of a patch pipette, the properties of the ionic channels produced by the ionophore toxin pardaxin were investigated. At low toxin concentrations, voltage-dependent, single-channel events were measured. The current-voltage curves were non-linear when determined in Tris-Cl solution, but were linear in K(+)-HEPES solution. Using asymmetric ion solutions, the ionic selectivity of pardaxin channels was estimated from the reversal potentials obtained. The sequence of the relative permeabilities for monovalent cations was Tl+ > Rb+ > Cs+ > K+,NH4+ > methylamine+ > Li+ > dimethylamine+ > Na+. Except for Li+, the selectivity sequence fitted the cations relative hydrated size. For bivalent ions the permeability of Ba2+, Sr2+, and Mn2+ relative to Mg2+ changed according to the relative hydrated size. For anions the selectivity sequence was I- > NO3- > Br- > Cl- > ClO4- > SCN- > BF- > HCOO- > F- > CH3COO-. The selectivity sequence for the small anions (I-, NO3-, Br-, Cl-) was different from their hydrated size. Pardaxin channel showed a modest ion selectivity between small anions and cations (PK:PCl:PNa = 1.28:1.00:0.56). Pardaxin is proposed as a biophysical model to study ionic channel selectivity.
采用膜片钳尖端双层膜的方法，研究了离子载体毒素豹蟾鱼毒素所产生的离子通道特性。在低毒素浓度下，测量了电压依赖性单通道事件。在Tris-Cl溶液中测定时，电流-电压曲线呈非线性，但在K(+)-HEPES溶液中呈线性。使用不对称离子溶液，根据获得的反转电位估计豹蟾鱼毒素通道的离子选择性。单价阳离子的相对渗透率顺序为Tl+ > Rb+ > Cs+ > K+，NH4+ > 甲胺+ > Li+ > 二甲胺+ > Na+。除Li+外，选择性顺序符合阳离子相对水合大小。对于二价离子，Ba2+、Sr2+和Mn2+相对于Mg2+的渗透率根据相对水合大小而变化。对于阴离子，选择性顺序为I- > NO3- > Br- > Cl- > ClO4- > SCN- > BF- > HCOO- > F- > CH3COO-。小阴离子（I-、NO3-、Br-、Cl-）的选择性顺序与其水合大小不同。豹蟾鱼毒素通道在小阴离子和阳离子之间表现出适度的离子选择性（PK:PCl:PNa = 1.28:1.00:0.56）。豹蟾鱼毒素被提议作为研究离子通道选择性的生物物理模型。
