Abstract: Thrombolytic hybrids are formed as covalent or non-covalent complexes of fibrin fragments and plasminogen activator molecules. Native plasmin degradation fragments of fibrin or non-native fibrin fragments are covalently or non-covalently linked to plasminogen activators such as t-PA, scu-PA, urokinase, streptokinase, and the like. Useful native fibrin fragments which may be utilized to form complexes with plasminogen activators include fragments E.sub.1, E.sub.2, E.sub.3, D and DD, and (DD)E complex. The fibrin fragment component targets the hybrid to vascular thrombi, immobilizing the plasminogen activator molecule onto the fibrin surface of the thrombus. Once localized on a thrombus surface, the plasminogen activator component of the hybrid activates only the clot-surface bound plasminogen transported by the fibrin fragment vehicle, without significant systemic activation of plasminogen.

Abstract: A purified peptide isolated from fibrinogen Fragment D.sub.1 and having the amino acid sequence Thr-Arg-Trp-Tyr-Ser-Met-Lys-Lys-Thr-Thr-Met-Lys-Ile-Ile-Pro-Phe-Asn-Arg-Le u-Thr-Ile-Gly-Glu-Gly-Gln-Gln-His-His-Leu-Gly-Gly-Ala-Lys-Gln-Ala-Gly-Asp-V al. The peptide is isloated by degrading Fragment D.sub.1 of fibrinogen with plasmin followed by separation of the resulting peptides on the basis of molecular weight and affinity for bound fibrin monomer. The purified peptide is useful as an anticoagulant and, when suitably labeled with a gamma-emitting radioisotope, as a thrombus imaging agent.

Abstract: A method of locating thrombi in vivo comprising the steps of administering a radiolabeled peptide selected from the group consisting of Fragment E.sub.1 isolated from cross-linked fibrin, Fragment E.sub.2 isolated from crosslinked fibrin, and peptides having an amino acid sequence intermediate between Fragments E.sub.1 and E.sub.2 derived from crosslinked fibrin by plasmin digestion to a human or animal wherein the peptide is selectively incorporated or bound by forming a pre-formed thrombi and externally detecting the radiation emitted by the radiolabeled peptide. A composition containing the peptide used for locating thrombi is also disclosed.

Abstract: Novel fibrinolytic factors obtained from the salivary glands of Haementeria ghilianii. Proteins having molecular weights under about 100,000 are isolated from the salivary glands of H. ghilianii. The proteins show cathodic mobility in electrophoresis and uninhibited peptidase activity with fibrinogen in plasma.