RESUMEN
Objective To investigate the effects of force on mechanical stability of FLNa-Ig21/αⅡbβ3-CT complex and the regulation mechanism.Methods The FLNa-Ig21/αⅡbβ3-CT crystal structures were taken from the PDB database.The stability of the complexes in a physiological environment as well as the unfolding path and mechanical stability induced by mechanical forces were analyzed using equilibrium and steered molecular dynamics simulations.Results During the equilibration,the survival rate of most salt bridge and hydrogen bonds was below 0.5,and the interactions between FLNa-Ig21 and αⅡbβ3-CT was relatively weak.During stretching at a constant velocity,the complex could withstand a tensile force of 70-380 pN,and its mechanical strength depended on the force-induced dissociation path.Under a constant force of 0-60 pN,the complexes exhibited a slipping-bond trend,and the force increase facilitated the breakage of the R995-D723 salt bridge and the activation of αⅡbβ3 integrin.Conclusions The force-induced allostery of αⅡbβ3-MP enhanced the complex mechanical strength and delayed FLNa-Ig21 dissociation from αⅡbβ3-CT.After breaking through the 20 pN threshold,force positively regulated the activation of αⅡbβ3 integrin.These results provide insights into the molecular mechanism of αⅡbβ3 activation and the development of related targeted drugs.
RESUMEN
Fibrinogen (Fg) in human plasma plays an important role in hemostasis, vascular repair and tissue integrity. The surface chemistry of extracellular matrix or biological materials affects the orientation and distribution of Fg, and changes the exposure of integrin binding sites, thereby affecting its adhesion function to platelets. Here, the quantity, morphology and side chain exposure of Fg adsorbed on hydrophilic, hydrophobic and avidin surfaces were measured by atomic force microscopy (AFM) and flow cytometry (FCM), then the rolling behavior of platelets on Fg was observed through a parallel plate flow chamber system. Our results show that the hydrophobic surface leads to a large amount of cross-linking and aggregation of Fg, while the hydrophilic surface reduces the adsorption and accumulation of Fg while causing the exposure and spreading of the α chain on Fg and further mediating the adhesion of platelets. Fg immobilized by avidin / biotin on hydrophilic surface can maintain the monomer state, avoid over exposure and stretching of α chain, and bind to the platelets activated by the A1 domain of von Willebrand factor instead of inactivated platelets. This study would be helpful for improving the blood compatibility of implant biomaterials and reasonable experimental design of coagulation