[Conformation of the fibrinogen molecule in solution: dynamic light scattering spectroscopy]

Human fibrinogen solutions were prepared either by filtration of ultracentrifugation. The sedimentation coefficient was S20,W = 7,9 S. The translational and the rotational diffusion coefficient DT and DR and the fraction of oligomers were determined using light beating spectroscopy. DT20,W was (2.03 +/- 1%) 10(-7)-cm2-sec-1, DR120,W = 40 000 +/- 10%-sec-1. The sedimentation coefficient and DT were strongly dependent on concentration. For pH values between 6.5 and 9.0, the diffusion coefficient DT at ionic strength greater than 0.2 was constant. The diffusion coefficient as measured by nanosecond fluorescence depolarization was DR//20,W = 1.6 x 10(6) sec-1. At a fibrinogen concentration of 2 mg/ml, these hydrodynamic data are compatible with an elongated molecule of 450 A length and an axial ratio of about 1:7.