polyP increases the thickness of fibrin fibrils. Clots were formed by preincubating 2.6 mg/mL of fibrinogen for 15 minutes in the presence of 2.5 mM CaCl2 plus the indicated polyP concentrations, after which clotting was initiated with 3 nM thrombin. (A) Mass-length ratios of the resulting fibrin preparations (relative to the condition without polyP), calculated from scans of optical densities from 400 to 800 nm as described in “Determination of fibril thickness.” Data are mean plus or minus SE (n = 4). (B) Fiber thickness is measured from scanning electron micrographs, as described in “Scanning electron microscopy.” Data are mean plus or minus SE (n = 120). (C-F) Representative scanning electron micrographs of fibrin clots formed in the presence of (C) no polyP, (D) 100 μM polyP, (E) 500 μM polyP, and (F) 1 mM polyP. Bar represents 2 μm.
