Snook Jeremy H, Guilford William H
Department of Biomedical Engineering, University of Virginia, 800759, Charlottesville, VA 22908, USA.
Cell Mol Bioeng. 2010 Jun 1;3(2):128-138. doi: 10.1007/s12195-010-0110-6.
Molecular dissociation rates have long been known to be sensitive to applied force. We use a laser trap to provide evidence that rates of association may also be force-dependent. We use the thermal fluctuation assay to study single bonds between E-selectin and sialyl Lewis(a) (sLe(a)), the sugar on PSGL-1 to which the three selectins bind. Briefly, an E-selectin-coated bead is held in a laser trap and pressed with various compressive loads against the vertical surface of a bead coated with sLe(a). The time it takes for a bond to form is used to calculate a specific two-dimensional on-rate, kono. We observe an increase in kono with increasing compressive force, providing single molecule evidence that on-rate, in addition to off-rate, is influenced by load. By measuring bond lifetimes at known tensile loads, we show that E-selectin, like its family members L- and P-selectin, is capable of forming catch bonds. Our data support a reverse Bell model, in which compressive forces lower the activation energy for binding. Load-dependent on-rates may be a general feature of all intermolecular bonds.
长期以来，人们一直知道分子解离速率对所施加的力很敏感。我们使用激光阱来提供证据，证明缔合速率也可能取决于力。我们使用热涨落测定法来研究E-选择素与唾液酸化路易斯抗原a（sLe(a)）之间的单键，sLe(a)是PSGL-1上三种选择素所结合的糖。简要地说，一个涂有E-选择素的珠子被捕获在激光阱中，并以各种压缩载荷压向一个涂有sLe(a)的珠子的垂直表面。键形成所需的时间用于计算特定的二维结合速率kono。我们观察到kono随着压缩力的增加而增加，提供了单分子证据表明结合速率除了解离速率之外，还受载荷影响。通过在已知拉伸载荷下测量键的寿命，我们表明E-选择素与其家族成员L-选择素和P-选择素一样，能够形成捕捉键。我们的数据支持一种反向贝尔模型，其中压缩力降低了结合的活化能。依赖于载荷的结合速率可能是所有分子间键的一个普遍特征。
