Merkel R, Nassoy P, Leung A, Ritchie K, Evans E
Department of Physics, University of British Columbia, Vancouver, Canada.
Nature. 1999 Jan 7;397(6714):50-3. doi: 10.1038/16219.
Atomic force microscopy (AFM) has been used to measure the strength of bonds between biological receptor molecules and their ligands. But for weak noncovalent bonds, a dynamic spectrum of bond strengths is predicted as the loading rate is altered, with the measured strength being governed by the prominent barriers traversed in the energy landscape along the force-driven bond-dissociation pathway. In other words, the pioneering early AFM measurements represent only a single point in a continuous spectrum of bond strengths, because theory predicts that these will depend on the rate at which the load is applied. Here we report the strength spectra for the bonds between streptavidin (or avidin) and biotins-the prototype of receptor-ligand interactions used in earlier AFM studies, and which have been modelled by molecular dynamics. We have probed bond formation over six orders of magnitude in loading rate, and find that the bond survival time diminished from about 1 min to 0.001 s with increasing loading rate over this range. The bond strength, meanwhile, increased from about 5 pN to 170 pN. Thus, although they are among the strongest noncovalent linkages in biology (affinity of 10(13) to 10(15) M(-1)), these bonds in fact appear strong or weak depending on how fast they are loaded. We are also able to relate the activation barriers derived from our strength spectra to the shape of the energy landscape derived from simulations of the biotin-avidin complex.
原子力显微镜（AFM）已被用于测量生物受体分子与其配体之间的键强度。但对于弱非共价键，随着加载速率的改变，预计会出现键强度的动态谱，所测量的强度由沿力驱动的键解离途径在能量景观中穿越的突出势垒决定。换句话说，早期具有开创性的AFM测量仅代表连续键强度谱中的一个单点，因为理论预测这些将取决于施加负载的速率。在此，我们报告了链霉亲和素（或抗生物素蛋白）与生物素之间键的强度谱——早期AFM研究中使用的受体 - 配体相互作用的原型，并且已经通过分子动力学进行了建模。我们在六个数量级的加载速率范围内探测了键的形成，发现在该范围内随着加载速率增加，键的存活时间从约1分钟减少到0.001秒。与此同时，键强度从约5皮牛增加到170皮牛。因此，尽管它们是生物学中最强的非共价键之一（亲和力为10^13至10^15 M^-1），但这些键实际上看起来强或弱取决于加载它们的速度有多快。我们还能够将从我们的强度谱得出的活化势垒与从生物素 - 抗生物素蛋白复合物模拟得出的能量景观形状联系起来。
