Nanostructure of the fibrin clot

Abstract

The nanostructure of the fibrin fibers in fibrin clots is investigated by using spectrometry and small angle x-ray scattering measurements. First, an autocoherent analysis of the visible light spectra transmitted through formed clots is demonstrated to provide robust measurements of both the radius and density of the fibrin fibers. This method is validated via comparison with existing small-angle and dynamic light-scattering data. The complementary use of small angle x-ray scattering spectra and light spectrometry unambiguously shows the disjointed nature of the fibrin fibers. Indeed, under quasiphysiological conditions, the fibers are approximately one-half as dense as their crystalline fiber counterparts. Further, although the fibers are locally crystalline, they appear to possess a lateral fractal structure.

Copyright © 2010 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Figures

Figure 1

Average fiber radius versus [Fg], IIa/[Fg] = 10−2, 300 mOsm. (Solid circles) This article. (Open circles) Data from Ferri et al. (19). (Shaded squares) Our data analyzed with the formula from Carr and Hermans (16).

Figure 2

Average number of protofibrils in the fibers versus the ionic strength ([Fg] = 1 mg/mL, IIa 1 UI/mL). (Solid circles) This article. (Shaded squares) Carr complete formula. (Open circles) Papi et al. (28). (Shaded circles) Carr approximate formula.

Figure 3

Plot of the average number of protofibrils in the fibers versus [Fg], IIa/[Fg] = 10−2, 300 mOsm. (Solid circles) This article. (Shaded squares) Carr complete formula. (Open squares) Carr's simplified formula at 350 nm.

Figure 4

SAXS spectrum of two clots in the same reaction conditions in logarithm scale (IIa: 1 UI/mL, [F]: 1 mg/mL [F], 300 mOsm). (Arrows) Main features of the internal structure of the fiber.

Figure 5

Average fiber radius in the catalytic regime versus [Fg] under ionic strength of 300 mOsm (solid circles) and 75 mOsm (open circles). (Inset, graph) Average number of protofibrils per cross section under the same conditions.

Figure 6

Average interprotofibril distance versus [Fg] in the catalytic regime under ionic strength of 300 mOsm (solid circles) and 75 mOsm (open circles). (Inset) Protein content versus [Fg]. The bold line corresponds to the density predicted by the model of Yang et al. (3).

Figure 7

Schematic of the internal structure of a fibrin fiber of diameter 75 nm using the model of Yang et al. (3). (a) Crystalline structure with a number of protofibrils of 60 (maximum possible density). (b) Structure with 25% of protofibrils removed with respect to panel a. (c) Structure with 50% of protofibrils removed with respect to panel a. This corresponds to the highest density measured with light spectroscopy.

Figure 8

Average number of protofibrils and protein mass concentration versus the ionic strength. [Fg] = 1 mg/mL and [IIa] = 1UI/mL. (Inset) Evolution of the protein concentration.

Figure 9

Average radius and interprotofibril distance versus the ionic strengths. [Fg] = 1 mg/mL and [IIa] = 1 UI/mL.