Petrossian A, Owicki J C
Biochim Biophys Acta. 1984 Oct 3;776(2):217-27. doi: 10.1016/0005-2736(84)90211-6.
Kinetic and equilibrium aspects of the recognition of antigenic model membranes by antibodies have been studied. Monoclonal anti-fluorescein IgG and its monovalent Fab fragment were allowed to interact with a fluorescein-lipid hapten that was incorporated into phospholipid vesicles. The binding was assayed in the nanomolar hapten concentration range by monitoring the quenching of hapten fluorescence by antibody. The rate and strength of the binding depended on the lipid composition of the vesicles; cholesterol enhanced both. The biphasic binding kinetics observed at high antibody concentrations for some compositions, plus additional spectroscopic evidence, led us to hypothesize that the hapten existed in a composition-dependent equilibrium between at least two conformations: (1) extended away from the membrane surface, available for binding, and (2) sequestered at or in the surface, unavailable for binding. The rate and strength of IgG binding were always greater than those of Fab, indicating bivalent binding by the IgG. This binding was intra-vesicular, since no agglutination of the vesicles was detected.
抗体识别抗原模型膜的动力学和平衡方面已得到研究。使单克隆抗荧光素IgG及其单价Fab片段与掺入磷脂囊泡中的荧光素 - 脂质半抗原相互作用。通过监测抗体对半抗原荧光的淬灭，在纳摩尔半抗原浓度范围内测定结合情况。结合的速率和强度取决于囊泡的脂质组成；胆固醇可增强两者。在某些组成的高抗体浓度下观察到的双相结合动力学，加上其他光谱学证据，使我们推测半抗原在至少两种构象之间存在组成依赖性平衡：（1）远离膜表面伸展，可用于结合；（2）隔离在表面或表面内，不可用于结合。IgG结合的速率和强度总是大于Fab，表明IgG的二价结合。这种结合是囊泡内的，因为未检测到囊泡的凝集。
