Cation Selectivity of Channels Formed at Planar Lipid Bilayer by Pinellia ternata Lectin

By means of the two-compartment system. PTL-channels, the first lectin channels formed on planar lipid bilayers by Pinellia ternata lectin (PTL) have been studied. The results show (i) PTL-channels are voltage-independent and have apparent subunits; (ii) in 50 mmol/L KC1 and 25 mmol/L BaCl2 solutions, a single channel has unit conductance of 21 pS and 42 pS, respectively; (iii) the channel exhibits a slightly higher permeability to divalent than monovalent cation (PBa/PK=4.1), and (iv) the selectivity among divalent or monovalent cations is poor. The cation selectivity sequence for the channel will follow PBa(7. 0)-Psr (6. 4)~PMg(6. 4)>PK(1. 7)>PN.(1. 0)~PLi(l. 0).Moreover, these data also give explanation to the facilitatory action of PTL on the release of acetyl-choline from motor nerve terminals.     

恒热流边界条件下流体横掠多孔介质中平板的边界层分析

基于Brinkman-Forchheimer-extended Darcy流动模型,对恒热流条件下流体横掠多孔介质中平板的强制对流进行了边界层分析。通过建立二维流动的连续方程、动量方程和考虑流体与多孔介质局部非热平衡时的能量方程,应用数量级分析和积分的方法对方程组进行简化和求解,得出了流体的速度分布、温度分布、速度边界层和温度边界层的厚度、对流传热的理论关联式。研究结果表明:恒热流条件下流体横掠多孔介质中平板的速度边界层与光板时完全不同,其在平板前端迅速增长,随后沿着流动方向变得非常平坦并趋于一定值;而温度边界层的厚度发展则与光板时类似,沿着流动方向不断增长,且与壁面处热流密度的大小无关。