The shape of the fibrinogen molecule: sausage or banana?

The experimental results and the interpretation of small angle X-ray scattering measurements by the author and Hammel (1975) and of small angle neutron scattering measurements by Marguerie and Stuhrmann (1976) on dilute solutions of bovine fibrinogen are compared. The potential of both methods to discern straight and bent cylindrical structures is demonstrated. The study arrives at the conclusion that the question whether the fibrinogen molecule resembles more a banana or a straight sausage cannot be safely decided by the available data. This justifies the previous suggestion of the author to imagine the fibrinogen molecule as a swollen sausage 450 A long and 90 A thick with conceivable flexibility, a molecular model of sufficient universality to include the banana-shaped model of Marguerie and Stuhrmann (1976) as a special case.