Fibrinogen is the blood protein at the centre of clotting and wound healing, and for more than 20 years scientists believed they knew how it behaves at surfaces: molecules were thought to lie flat at low concentrations, then tilt upright as more arrive, forming a single crowded layer. A study involving the University of Manchester, the University of Santiago de Compostela, Metropolitan Technological University in Chile, Lund University and the Institut Laue-Langevin in France has now overturned that picture.
Using neutron reflectometry on the FIGARO instrument at the Institut Laue-Langevin, the team examined fibrinogen layers at the air-water interface across a range of concentrations and solution conditions. Rather than tilting upright, the protein stays flat and builds multiple stacked layers that grow thicker and more complete over time, a behaviour that proved consistent across all the conditions tested. The results are published in the Journal of the American Chemical Society.
The revised model has implications well beyond protein physics. Stacked fibrinogen layers may help explain how scabs form at the surface of blood, how fibrinogen disrupts lung surfactant in acute respiratory distress syndrome, and how biosensors that detect proteins at interfaces should be engineered. It is a reminder that even textbook molecules can behave unexpectedly when examined with sufficiently penetrating instruments.