Observing the dynamic variation of the binding force between rhodostomin ligand and integrin alpha (IIb) beta (3) receptor using a photonic force microscope

The conformational change of integrin α _IIbβ ₃ plays an important role in clot formation. However, the correlation between the structure and the function of integrin α _IIbβ ₃ in interacting with its ligand is still not clear. In this report, we focus on the dynamic variation of the binding between integrin α _IIbβ ₃ and its ligand, rhodostomin by using a photonic force microscopy (PFM). The PFM is used to trap a rhodostomin-coated bead and, then, shift it to bind a surrounding CHO α _IIbβ ₃ cell. Meanwhile, it tracks, with a resolution of 1MHz, the Brownian fluctuations of the trapped bead Theoretically, the smaller the amplitude of the Brownian fluctuations, the stronger the stiffness of the binding force between the rhodostomin and the CHO α _IIbβ ₃ cell. Experimentally, a significant decrease of the Brownian fluctuations was observed during the interval between the 360 ^th seconds and the 400 ^th seconds after the trapped rhodostomin-coated bead contacted an integrin-expressed CHO α _IIbβ ₃ cell. This observation reveals that it takes the rhodostomin 360 seconds to seek the correct position to bind to the integrin α _IIbβ ₃. After 400 seconds, the rhodostomin has bound rigidly with the integrin α _IIbβ ₃. We presume that the integrin α _IIbβ ₃ has reached its final stage of conformational change.