Heinrich V, Waugh R E
Department of Biophysics, University of Rochester School of Medicine and Dentistry, NY 14642, USA.
Ann Biomed Eng. 1996 Sep-Oct;24(5):595-605. doi: 10.1007/BF02684228.
The bending stiffness of a phospholipid bilayer (Kc) was measured by forming thin bilayer cylinders (tethers) from giant phospholipid vesicles. Based on the balance of forces, the tether force was expected to be proportional to the square root of the membrane tension, with a constant of proportionality containing Kc. The membrane tension was controlled via the aspiration pressure in a micropipette used to hold the vesicle. The force on the tether was generated by an electromagnet acting on a paramagnetic bead attached to the vesicle surface. The magnitude of the force was determined from measurements of the magnet current, which was adjusted to maintain the position of the bead. Measurements were performed on vesicles composed of stearoyl-oleoyl-phosphatidylcholine plus 5% (by mole) biotinylated phosphatidylethanolamine to mediate adhesion to streptavidin-coated beads. From each vesicle, tethers were formed repeatedly at different values of the membrane tension. The expected relationship between membrane tension and tether force was observed. The mean value of Kc for 10 different vesicles was 1.17 x 10(-19) J (SD = 0.08 x 10(-19) J). The precision of these data demonstrates the reliability of this approach, which avoids uncertainties of interpretation and measurement that may be associated with other methods for determining Kc.
通过从巨型磷脂囊泡形成薄双层圆柱体（系链）来测量磷脂双层的弯曲刚度（Kc）。基于力的平衡，系链力预计与膜张力的平方根成正比，比例常数包含Kc。通过用于固定囊泡的微量移液器中的抽吸压力来控制膜张力。系链上的力由作用于附着在囊泡表面的顺磁珠的电磁铁产生。力的大小由磁体电流的测量值确定，该电流经过调整以保持珠子的位置。对由硬脂酰油酰磷脂酰胆碱加5%（摩尔）生物素化磷脂酰乙醇胺组成的囊泡进行测量，以介导与链霉亲和素包被珠子的粘附。从每个囊泡中，在不同的膜张力值下反复形成系链。观察到了膜张力与系链力之间的预期关系。10个不同囊泡的Kc平均值为1.17×10^(-19) J（标准差 = 0.08×10^(-19) J）。这些数据的精度证明了这种方法的可靠性，它避免了可能与其他测定Kc的方法相关的解释和测量的不确定性。
