Fragment antigen-binding

A concrete comparison used a Biacore T100 with a CM5 chip bearing the target <receptor>; unused reactive surface groups were blocked. At $25\,{}^{\circ}\mathrm{C}$ in a <pH> 7.4 <buffer solution>, intact <IgG> and its <Fab fragment> were injected for $180\,\mathrm s$ at $5\,\mu\mathrm L/\mathrm{min}$; dissociation was monitored for $3600\,\mathrm s$. The optical response tracks changes in <refractive index> near the surface, rather than counting occupied <paratopes> directly. A reference surface and blank injections corrected background; association and dissociation responses were fitted with a 1:1 model. The reported intact-<IgG> detachment was slower than that of the <Fab fragment>. <Antibody-Unfolding and Metastable-State Binding in Force Spectroscopy and Recognition Imaging by Parminder Kaur and others>[Kaur and others, Materials and Methods, Surface plasmon resonance; Table 1, whole IgG and Fab rows]{ref}

This comparison supports format-dependent attachment, not an intrinsic single-site <antibody affinity> for intact <IgG>. The reference and blanks address background, not two-arm <avidity>, surface accessibility or delivery by <diffusion>. The paper's fitted 1:1 constants alone cannot distinguish those mechanisms. Its <Fab fragment> comparison therefore motivates specifying the binding format before interpreting a <dissociation constant>; a good fit does not establish a unique molecular model.


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 Incoming links: Antibody surface plasmon resonance experiment