Article Information

• PDF (2451 kb)

PubMed

• Articles by J.P. Collet
• Articles by J.W. Weisel

Related Articles

• Visualization and Mechanical Manipulations of Individual Fib...

  Visualization and Mechanical Manipulations of Individual Fibrin Fibers Suggest that Fiber Cross Section Has Fractal Dimension 1.3 Biophysical Journal, Volume 87, Issue 6, 1 December 2004, Pages 4226-4236 M. Guthold, W. Liu, B. Stephens, S.T. Lord, R.R. Hantgan, D.A. Erie, R.M. Taylor and R. Superfine Abstract We report protocols and techniques to image and mechanically manipulate individual fibrin fibers, which are key structural components of blood clots. Using atomic force microscopy-based lateral force manipulations we determined the rupture force, , of fibrin fibers as a function of their diameter, , in ambient conditions. As expected, the rupture force increases with increasing diameter; however, somewhat unexpectedly, it increases as ∼ . Moreover, using a combined atomic force microscopy-fluorescence microscopy instrument, we determined the light intensity, , of single fibers, that were formed with fluorescently labeled fibrinogen, as a function of their diameter, . Similar to the force data, we found that the light intensity, and thus the number of molecules per cross section, increases as ∼ . Based on these findings we propose that fibrin fibers are fractals for which the number of molecules per cross section increases as about . This implies that the molecule density varies as () ∼ , i.e., thinner fibers are denser than thicker fibers. Such a model would be consistent with the observation that fibrin fibers consist of 70–80% water and only 20–30% protein, which also suggests that fibrin fibers are very porous. Abstract | Full Text | PDF (580 kb)

• Cl Regulates the Structure of the Fibrin Clot

  Cl Regulates the Structure of the Fibrin Clot Biophysical Journal, Volume 75, Issue 4, 1 October 1998, Pages 1973-1979 Enrico Di Stasio, Chandrasekaran Nagaswami, John W. Weisel and Enrico Di Cera Abstract The differences between coarse and fine fibrin clots first reported by Ferry have been interpreted in terms of nonspecific ionic strength effects for nearly 50 years and have fostered the notion that fibrin polymerization is largely controlled by electrostatic forces. Here we report spectroscopic and electron microscopy studies carried out in the presence of different salts that demonstrate that this long-held interpretation needs to be modified. In fact, the differences are due entirely to the specific binding of Cl to fibrin fibers and not to generic ionic strength or electrostatic effects. Binding of Cl opposes the lateral aggregation of protofibrils and results in thinner fibers that are also more curved than those grown in the presence of inert anions such as F. The effect of Cl is pH dependent and increases at pH>8.0, whereas fibers grown in the presence of F remain thick over the entire pH range from 6.5 to 9.0. From the pH dependence of the Cl effect it is suggested that the anion exerts its role by increasing the pK of a basic group ionizing around pH 9.2. The important role of Cl in structuring the fibrin clot also clarifies the role played by the release of fibrinopeptide B, which leads to slightly thicker fibers in the presence of Cl but actually reduces the size of the fibers in the presence of F. This effect becomes more evident at high, close to physiological concentrations of fibrinogen. We conclude that Cl is a basic physiological modulator of fibrin polymerization and acts to prevent the growth of thicker, stiffer, and straighter fibers by increasing the pK of a basic group. This discovery opens new possibilities for the design of molecules that can specifically modify the clot structure by targeting the structural domains responsible for Cl binding to fibrin. Abstract | Full Text | PDF (400 kb)

• Influence of a Natural and a Synthetic Inhibitor of Factor X...

  Influence of a Natural and a Synthetic Inhibitor of Factor XIIIa on Fibrin Clot Rheology Biophysical Journal, Volume 77, Issue 5, 1 November 1999, Pages 2827-2836 Esther A. Ryan, Lyle F. Mockros, Andrew M. Stern and Laszlo Lorand Abstract We investigated the origins of greater clot rigidity associated with FXIIIa-dependent cross-linking. Fibrin clots were examined in which cross-linking was controlled through the use of two inhibitors: a highly specific active-center-directed synthetic inhibitor of FXIIIa, 1,3-dimethyl-4,5-diphenyl-2[2(oxopropyl)thio]imidazolium trifluoromethylsulfonate, and a patient-derived immunoglobulin directed mainly against the thrombin-activated catalytic A subunits of thrombin-activated FXIII. Cross-linked fibrin chains were identified and quantified by one- and two-dimensional gel electrophoresis and immunostaining with antibodies specific for the - and -chains of fibrin. Gamma-dimers, -multimers, -polymers, and -hybrids were detected. The synthetic inhibitor was highly effective in preventing the production of all cross-linked species. In contrast, the autoimmune antibody of the patient caused primarily an inhibition of -chain cross-linking. Clot rigidities (storage moduli, ′) were measured with a cone and plate rheometer and correlated with the distributions of the various cross-linked species found in the clots. Our findings indicate that the FXIIIa-induced dimeric cross-linking of -chains by itself is not sufficient to stiffen the fibrin networks. Instead, the augmentation of clot rigidity was more strongly correlated with the formation of -multimers, -polymers, and -hybrid cross-links. A mechanism is proposed to explain how these cross-linked species may enhance clot rigidity. Abstract | Full Text | PDF (301 kb)

• …more

Abstract

Ultrastructural perturbations resulting from defects in polymerization of fibrinogen Dusart, a congenital dysfibrinogenemia with the amino acid substitution A alpha 554 arginine to cysteine, were investigated by a variety of electron microscope studies. Polymerization of this mutant fibrinogen on addition of thrombin is impaired, producing clots with decreased porosity and increased resistance to fibrinolysis, resulting in thrombotic complications in the family members with this dysfibrinogenemia. Electron microscopy of rotary-shadowed individual molecules revealed that, in contrast to control fibrinogen, most of the alpha C domains of fibrinogen or fibrin Dusart appeared to be free-swimming appendages that do not exhibit intra- or intermolecular interactions either with each other or with the central domains. The location of albumin on the alpha C domains was demonstrated by electron microscopy using anti-albumin antibodies. Electron microscopy of negatively contrasted fibrin Dusart fibers indicated that they were less ordered than control fibers and had additional mass visible. Electron microscopy of freeze-dried, unidirectionally shadowed fibers showed that they were twisted with a shorter pitch. Scanning electron microscopy revealed that intact clots were made up of thin fibers with many branch points and very small pore sizes. The viscoelastic properties of Dusart fibrin clots measured with a torsion pendulum indicated a marked increase in stiffness consistent with the structural observations.