DETERMINATION OF THE LIFETIME AND FORCE DEPENDENCE OF INTERACTIONS OFSINGLE BONDS BETWEEN SURFACE-ATTACHED CD2 AND CD48 ADHESION MOLECULES

We studied single molecular interactions between surface-attached rat CD2, a T-lymphocyte adhesion receptor, and CD48, a CD2 ligand found on antigen-presenting cells, Spherical particles were coated with decrea sing densities of CD48-CD4 chimeric molecules then driven along CD2-de rivatized glass surfaces under a low hydrodynamic shear rate, Particle s exhibited multiple arrests of varying duration, By analyzing the dep endence of arrest frequency and duration on the surface density of CD4 8 sites, it was concluded that (i) arrests were generated by single mo lecular bonds and (ii) the initial bond dissociation rate was about 7. 8 s(-1). The force exerted on bonds was increased from about 11 to 22 pN; the detachment rate exhibited a twofold increase. These results ag ree with and extend studies on the CD2-CD48 interaction by surface pla smon resonance technology, which yielded an affinity constant of appro ximate to 10(4) M(-1) and a dissociation rate of greater than or equal to 6 s(-1). It is concluded that the flow chamber technology can be a n useful complement to atomic force microscopy for studying interactio ns between isolated biomolecules, with a resolution of about 20 ms and sensitivity of a few piconewtons. Further, this technology might be e xtended to actual cells.