FORMATION OF BIMOLECULAR MEMBRANES FROM LIPID MONOLAYERS AND A STUDY OF THEIR ELECTRICAL PROPERTIES
FORMATION OF BIMOLECULAR MEMBRANES FROM LIPID MONOLAYERS AND A STUDY OF THEIR ELECTRICAL PROPERTIES
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DOI：
10.1073/pnas.69.12.3561
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发表时间：
1972-01-01
影响因子：
11.1
通讯作者：
MUELLER, P
中科院分区：
文献类型：
--
作者：
MONTAL, M;MUELLER, P
当分离两个水相的聚四氟乙烯隔板中的孔下降通过界面时，双分子膜由空气-水界面上的两个脂质单层通过它们的烃链并置而形成。通过用电压钳测量的电容的增加来监测膜的形成。未改性膜的电阻类似于在烃溶剂存在下制备的传统平面双层（黑色脂质膜）的电阻，即106-108ohm cm2；短杆菌肽可将电阻降低至 103ohm cm2，短杆菌肽是一种抗生素，仅当膜具有生物分子厚度时才会改变电导。与电阻相反，由单层制成的双层与由相变制成的含烃双层的容量存在显着差异；平均值分别为 0.9 和 0.45 μF cm-2。 0.9 μF cm-2 的值近似于生物膜的值。假设碳氢化合物区域的介电常数为 2.1，则根据 0.9 μF cm-2 的容量计算得出的电介质厚度为 22 Å。通过 X 射线衍射测定，该值比双层和细胞膜碳氢化合物区域的实际厚度小 6-10 Å。差异可能是由于水渗透到酯基附近的烃区域有限，这会降低该区域的电阻并减小电介质厚度。不对称膜是由相邻的两个不同化学成分的脂质单层形成的。
Bimolecular membranes are formed from two lipid monolayers at an air-water interface by the apposition of their hydrocarbon chains when an aperture in a Teflon partition separating two aqueous phases is lowered through the interface. Formation of the membrane is monitored by an increase of the electrical capacity, as measured with a voltage clamp. Electrical resistance of the unmodified membrane is analogous to that of conventional planar bilayers (black lipid membranes) prepared in the presence of a hydrocarbon solvent, i.e., 106-108ohm cm2; the resistance can be lowered to values of 103ohm cm2by gramicidin, an antibiotic that modifies the conductance only when the membranes are of biomolecular thickness. In contrast to the resistance, there is a significant difference between the capacity of bilayers made from mono-layers and that of hydrocarbon-containing bilayers made by phase transition; the average values are 0.9 and 0.45 μF cm-2, respectively. The value of 0.9 μF cm-2approximates that of biological membranes. Assuming a dielectric constant of 2.1 for the hydrocarbon region, the dielectric thickness, as calculated from a capacity of 0.9 μF cm-2, is 22 Å. This value is 6-10 Å smaller than the actual thickness of the hydrocarbon region of bilayers and cell membranes, as determined by x-ray diffraction. The difference may be due to a limited penetration of water into the hydrocarbon region near the ester groups that would lower the electrical resistance of this region and reduce the dielectric thickness. Asymmetric membranes have been formed by adjoining two lipid monolayers of different chemical composition.