非特异性相互作用的断裂力与寿命测量

目的　探讨量化非特异性相互作用在特异性选择素－配体分子相互作用中的贡献。方法　利用光镊技术，对牛血清白蛋白(Bovine serum albumin, BSA)封闭的玻璃小球间的非特异性作用进行了系统测量，得出不同加载率下的断裂力以及不同外力作用下的寿命分布。结果　实验结果表明，非特异性作用同样表现出断裂力随加载率增加而增大的趋势。在较低加载率下，非特异性断裂力与选择素－配体特异性断裂力大小、增大趋势基本一致；随着加载率增加，二者的差别逐渐显著，前者的断裂力增加速率远低于后者。同样外力作用下，非特异性作用的寿命平均值比特异性作用要小；不同外力作用下，非特异性作用的寿命随外力增大仅略有下降，与特异性作用中逆锁键－滑移键转化现象有明显不同。结论　该研究结果将为正确评估非特异性相互作用对选择素－配体特异性相互作用实验结果的影响提供基础。

Rupture Force and Lifetime Distributions of non-specific Interactions

Objective Quantifying the contribution of the non-specific interactions to the specific selection-ligand bidings. Methods We used optical tweezers to quantify the non-specific interaction dependence of bond rupture forces on loading rates and of bond lifetimes on applied forces by measuring the adhesions between two BSA (Bovine serum albumin)-coated glass beads. Results The results indicated that the rupture force dependence for non-specific interactions under lower loading rates presented from the similar transition phase as that for specific selectin-ligand bindings. While the differences in rupture force between non-specific and specific interactions became more and more evident with increase of loading rates, the increase rate of rupture force for non-specific interactions was much lower than that for selectin-ligand bindings. Under the same external force, the mean lifetime for non-specific interactions was lower than that for specific bindings. Lifetime for non-specific interactions decreased slightly with increase of applied forces, and no transition phases between slip and catch bonds were found. Conclusion This work provides the bases for quantitatively evaluating the effect of non-specific interactions in measuring selectin-ligand bindings.