Lipids were obtained from high potassium (HK) and low potassium (LK) sheep red cells by sequential extraction of the erythrocytes with isopropanol-chloroform, chloroform-methanol-0.1 M KCl, and chloroform. The extract contained cholesterol and phospholipid in a molar ratio of 0.8:1.0, and less than 1% protein contaminant. Stable thin lipid membranes separating two aqueous compartments were formed from an erythrocyte lipid-hydrocarbon solution, and had an electrical resistance of ∼108 ohm-cm2 and a capacitance of 0.38–0.4 µf/cm2. From the capacitance values, membrane thickness was estimated to be 46–132 A, depending on the assumed value for the dielectric constant (2.0–4.5). Membrane voltage was recorded in the presence of ionic (NaCl and/or KCl) concentration gradients in the solutions bathing the membrane. The permeability of the membrane to Na+, K+, and Cl- (expressed as the transference number, T ion) was computed from the steady-state membrane voltage and the activity ratio of the ions in the compartments bathing the membrane. T Na and T K were approximately equal (∼0.8) and considerably greater than T Cl (∼0.2). The ionic transference numbers were independent of temperature, the hydrocarbon solvent, the osmolarity of the solutions bathing the membranes, and the cholesterol content of the membranes, over the range 21–38°C. The high degree of membrane cation selectivity was tentatively attributed to the negatively charged phospholipids (phosphatidylethanolamine and phosphatidylserine) present in the lipid extract.
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机译:通过依次用异丙醇-氯仿,氯仿-甲醇-0.1 M KCl和氯仿提取红细胞,从高钾(HK)和低钾(LK)绵羊红细胞中获得脂质。提取物所含的胆固醇和磷脂的摩尔比为0.8:1.0,蛋白质污染物少于1%。由红细胞脂质-碳氢化合物溶液形成的稳定的脂膜将两个水室分隔开,其电阻约为10 8 sup> ohm-cm 2 sup>,电容量为0.38 –0.4 µf / cm 2 sup>。根据电容值,膜厚度估计为46–132 A,这取决于介电常数(2.0–4.5)的假设值。在冲洗膜的溶液中存在离子(NaCl和/或KCl)浓度梯度的情况下记录膜电压。膜对Na + sup>,K + sup>和Cl - sup>的渗透率(表示为迁移数,T离子)是通过计算稳态膜电压和镀膜槽中离子的活度比。 T Na和T K大约等于(〜0.8),并且大大大于T Cl(〜0.2)。在21–38°C范围内,离子迁移数与温度,烃溶剂,浸入膜的溶液的渗透压和膜中的胆固醇含量无关。膜阳离子选择性的高水平暂时归因于脂质提取物中存在的带负电荷的磷脂(磷脂酰乙醇胺和磷脂酰丝氨酸)。
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