Fritz J, Katopodis A G, Kolbinger F, Anselmetti D
Novartis Services AG, Scientific Services, Physics, WKL-127.620, CH-4002 Basel, Switzerland.
Proc Natl Acad Sci U S A. 1998 Oct 13;95(21):12283-8. doi: 10.1073/pnas.95.21.12283.
Leukocytes roll along the endothelium of postcapillary venules in response to inflammatory signals. Rolling under the hydrodynamic drag forces of blood flow is mediated by the interaction between selectins and their ligands across the leukocyte and endothelial cell surfaces. Here we present force-spectroscopy experiments on single complexes of P-selectin and P-selectin glycoprotein ligand-1 by atomic force microscopy to determine the intrinsic molecular properties of this dynamic adhesion process. By modeling intermolecular and intramolecular forces as well as the adhesion probability in atomic force microscopy experiments we gain information on rupture forces, elasticity, and kinetics of the P-selectin/P-selectin glycoprotein ligand-1 interaction. The complexes are able to withstand forces up to 165 pN and show a chain-like elasticity with a molecular spring constant of 5.3 pN nm-1 and a persistence length of 0.35 nm. The dissociation constant (off-rate) varies over three orders of magnitude from 0.02 s-1 under zero force up to 15 s-1 under external applied forces. Rupture force and lifetime of the complexes are not constant, but directly depend on the applied force per unit time, which is a product of the intrinsic molecular elasticity and the external pulling velocity. The high strength of binding combined with force-dependent rate constants and high molecular elasticity are tailored to support physiological leukocyte rolling.
白细胞会响应炎症信号，沿着毛细血管后微静脉的内皮滚动。在血流的流体动力学拖曳力作用下的滚动，是由选择素与其跨白细胞和内皮细胞表面的配体之间的相互作用介导的。在此，我们通过原子力显微镜对P-选择素和P-选择素糖蛋白配体-1的单一复合物进行力谱实验，以确定这种动态粘附过程的内在分子特性。通过在原子力显微镜实验中对分子间力、分子内力以及粘附概率进行建模，我们获得了关于P-选择素/P-选择素糖蛋白配体-1相互作用的断裂力、弹性和动力学的信息。这些复合物能够承受高达165皮牛的力，并表现出链状弹性，分子弹簧常数为5.3皮牛·纳米⁻¹，持久长度为0.35纳米。解离常数（解离速率）在三个数量级范围内变化，从零力下的0.02秒⁻¹到外部施加力下的15秒⁻¹。复合物的断裂力和寿命并非恒定不变，而是直接取决于单位时间内施加的力，该力是内在分子弹性与外部牵拉速度的乘积。结合力的高强度、与力相关的速率常数以及高分子弹性，都是为支持生理性白细胞滚动而量身定制的。
