E. coli O111:B4 LPS and human plasma fibrinogen were purchased from Sigma-Aldrich. Samples were reconstituted in warm phosphate buffered saline and incubated for 1 h at 37°C with shaking. LPS was then sonicated for 1 h at 60°C. Fibrinogen solutions were passed through a 0.2 µm polyethersulfone syringe filter and concentrations were determined by UV absorbance (E1% = 15.1 at 280 nm). Samples were then diluted with buffer to the required concentration and degassed. ITC experiments were performed at 37°C on a MicroCal Auto-iTC200 system (GE Healthcare) in high-gain mode at a reference power of 10 µcal s−1, with an initial 0.5 µl (1 s) injection followed by 15 2.5 µl (5 s) injections with 300 s spacing. For longer titrations, the syringe was refilled and injections continued into the same cell sample. Control runs were performed in which cell samples were titrated with buffer and syringe samples were titrated into buffer, and data from these runs were subtracted from the experimental data as appropriate. Data analysis was performed in Origin, using the supplied software (MicroCal).