title: Surface-bound selectin-ligand binding is regulated by carrier diffusion.
abstract: Two-dimensional (2D) kinetics of receptor-ligand interactions governs cell adhesion in many biological processes. While the dissociation kinetics of receptor-ligand bond is extensively investigated, the association kinetics has much less been quantified. Recently receptor-ligand interactions between two surfaces were investigated using a thermal fluctuation assay upon biomembrane force probe technique (Chen et al. in Biophys J 94:694-701, 2008). The regulating factors on association kinetics, however, are not well characterized. Here we developed an alternative thermal fluctuation assay using optical trap technique, which enables to visualize consecutive binding-unbinding transition and to quantify the impact of microbead diffusion on receptor-ligand binding. Three selectin constructs (sLs, sPs, and PLE) and their ligand P-selectin glycoprotein ligand 1 were used to conduct the measurements. It was indicated that bond formation was reduced by enhancing the diffusivity of selectin-coupled carrier, suggesting that carrier diffusion is crucial to determine receptor-ligand binding. It was also found that 2D forward rate predicted upon first-order kinetics was in the order of sPs > sLs > PLE and bond formation was history-dependent. These results further the understandings in regulating association kinetics of surface-bound receptor-ligand interactions.
authors.affiliation: National Microgravity Laboratory and Center for Biomechanics and Bioengineering, Institute of Mechanics, Chinese Academy of Sciences, Beijing, PR China.
authors.forename: Ganyun
authors.initials: G
authors.lastname: Sun
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhang
authors.forename: Bo
authors.initials: B
authors.lastname: Huo
authors.forename: Mian
authors.initials: M
authors.lastname: Long
mesh_terms: D000818:Animals; D002448:Cell Adhesion; D004058:Diffusion; D007700:Kinetics; D007834:Lasers; D008024:Ligands; D008562:Membrane Glycoproteins / Q000378:metabolism*; D052898:Optical Tweezers; D011485:Protein Binding; D019087:Selectins / Q000378:metabolism*; D013499:Surface Properties; D013696:Temperature
chemical_list: D008024:Ligands; D008562:Membrane Glycoproteins; C084882:P-selectin ligand protein; D019087:Selectins