Quasi-elastic light scattering from fibrinogen and fibrin intermediate structures |
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Authors: | Michael Müller Walther Burchard |
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Institution: | Institute of Macromolecular Chemistry, University of Freiburg, W. Germany |
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Abstract: | Quasi-elastic light scattering measurements have been carried out for (i) human and bovine fibrinogens under identical conditions, (ii) for a large number of fractionated and unfractionated fibrin intermediates at various pH (10.0 to 10.5), (iii) for three intermediates polymerized at pH 7.4 and stabilized at pH 10.5 and (iv) for a gelled clot. Human and bovine fibrinogen proved to have noticeably different diffusion coefficients (same Mw) indicating a longer rod on the average for the human than for the bovine fibrinogen. This finding is in agreement with measurements of the integrated light scattering from these fibrinogens where a mass per unit length of 3860 and 5460 g mol?1 nm?1 were found, respectively. No angular dependence of the apparent diffusion coefficient Dapp = Γ/q2 was found for the monomers and the fibrin clot; all other samples from (ii) showed an angular dependence if Mw ? 1.76 × 106, were Γ is the first cumulant of the time correlation function and q = (4π/λ) sin?/2. A plot of Dapp/D versus q2〈S2〉 gave curves which, for the low molecular weight samples, correspond to ellipsoids. For the longer fibrils a dynamic behaviour in between that of a long rigid rod and random coil was found and indicates a certain flexibility of the fibrils. The diffusion coefficients from (ii) decay with increasing molecular weight and can be described by Perrin's theory for ellipsoids when M2 < 2 × 106 while a beter agreement with Kirkwood's theory of long rods is obtained for the longer fibrils. The hydrodynamic behaviour of (iii) indicates short and unbranched rods of considerable thickness. |
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