Shadow-cast Electron Microscopy of Fibrinogen with Antibody Fragments Bound to Specific Regions
Overview
Authors
Affiliations
Specimens of human fibrinogen mixed with Fab fragments of antibodies that were specific for various portions of the fibrinogen molecule were tungsten shadow-cast and examined by electron microscopy. Typical trinodular fibrinogen molecules were observed when Fab fragments were omitted or when fragments from nonimmune sera were used. In the experimental fibrinogen-Fab preparations, a significant number of molecules were found with an extra nodule. In the case of Fab fragments from antibodies directed to fragment E, the additional nodule was attached to the central sphere of the fibrinogen molecule. Similarly, anti-fragment D preparations yielded molecules that were derivatized on the terminal spheres. Fragments from antibodies raised against a cyanogen bromide fragment of fibrinogen alpha chains (residues 241-476) also led to exclusive derivatization of the terminal domains, although in these cases the additional material was often separated discretely from the terminal sphere by a gap. These experiments confirm longstanding notions that the central domain of a trinodular fibrinogen molecule corresponds to the plasmin-derived fragment E and that the terminal spheres correspond to fragments D. Moreover, the carboxy-terminal two-thirds of alpha chains protrude from the extremities of the molecule, as had been inferred on the basis of indirect biochemical data.
Fib420: a normal human variant of fibrinogen with two extended alpha chains.
Fu Y, Grieninger G Proc Natl Acad Sci U S A. 1994; 91(7):2625-8.
PMID: 8146165 PMC: 43422. DOI: 10.1073/pnas.91.7.2625.
Fibrinogen and fibrin structure and fibrin formation measured by using magnetic orientation.
Freyssinet J, Torbet J, Maret G Proc Natl Acad Sci U S A. 1983; 80(6):1616-20.
PMID: 6572926 PMC: 393653. DOI: 10.1073/pnas.80.6.1616.
Immune labeling of the D and E regions of human fibrinogen by electron microscopy.
Norton P, Slayter H Proc Natl Acad Sci U S A. 1981; 78(3):1661-5.
PMID: 6453348 PMC: 319192. DOI: 10.1073/pnas.78.3.1661.