Figure 2.

GPIbαN unfolding observed by BFP force-clamp assay. (A) BFP photomicrograph. A micropipette-aspirated RBC with a bead (left, probe) attached to the apex formed a picoforce sensor. It was aligned with another bead (right, target) aspirated by an apposing micropipette. (B) BFP functionalization with indicated molecules. (C and D) Force versus time traces from representative force-clamp cycles for A1-GC bond lifetime measurement (C) and antibody-protein stretch assay (D). (Inset) The putative unfolding event is circled and zoomed-in to show the details. (E) Occurrence frequencies of unfolding-versus-no-unfolding events (numbers are indicated in yellow) from all binding events mediated by the indicated interactions. (F) Normalized histograms (bar) and their Gaussian fits of unfolding length. (G) Glycocalicin schematic (left) and GPIbαN domain organization (right). Starting and ending residues for each domain as well as the binding epitopes of two anti-GPIbα mAbs are all indicated. To see this figure in color, go online.