Radiolabeled anticoagulant peptides

A radio-labeled peptide derivative of the formula I (ID#26):

• (1)X-A.sub.1 -A.sub.2 -A.sub.3 -A.sub.4 -A.sub.5 -A.sub.6 -A.sub.7 -A.sub.8 -A.sub.9 -A.sub.10 -Y
• wherein;
• X is an amino terminal substituent selected from hydrogen, one or two alkyl groups of from 1 to 10 carbon atoms, one or two acyl groups of from 2 to 10 carbon atoms, carbobenzyloxy or t-butyloxy carbonyl;
• A.sub.1 is a sequence of 1-11 amino acids of hirudin (SEQ ID NO:1), or known naturally occurring amino acid sequence variation of hirudin (SEQ ID NO:2;
• SEQ ID NO:3), or a bond;
• A.sub.2 is one to five residues of [.sup.3 H]-Tyr, [.sup.125 I]-Tyr, [.sup.131 I]-Tyr;
• unless A.sub.9 contains a radio-labeled amino acid then A.sub.2 can additionally be I-Tyr, Tyr, or a bond;
• A.sub.3 is Glu, or Asp;
• A.sub.4 is Pro, or Glu;
• A.sub.5 is Ile;
• A.sub.6 is Tiq, Pro, Hyp, 3,4-dihydroPro, thiazolidine-4-carboxylate, Sar, NMePgl, Azt, or Pip;
• A.sub.7 is Glu, or Asp;
• A.sub.8 is Glu, Asdp, or Ala;
• A.sub.9 is a lipophilic amino acid selected from Tyr, I-Tyr, [.sup.125 I]-Tyr, [.sup.131 I]-Tyr, [.sup.3 H]-Tyr, Met, Trp, Phe, Leu, Nle, Ile, Val, Cha, His, Ala and Pro or is a dipeptide containing at least one of these amino acids and a amino acid found in hirudin (SEQ ID NO:1), or known naturally occurring amino acid sequence variation of hirudin (SEQ ID NO:2;
• SEQ ID NO:3);
• A.sub.10 is a sequence of 1-11 amino acids of hirudin (SEQ ID NO:1), or known naturally occurring amino acid sequence variation of hirudin (SEQ ID NO:2;
• SEQ ID NO:3), D-Glu, Glu, Gln, Asn, or a bond;
• Y is a carbonyl substituent (--CO--) of the terminal amino acid selected from OH, (C.sub.1 -C.sub.8) alkoxy, amino, or a mono or di (C.sub.1 -C.sub.4) alkyl substituted amino group;
• or the terminal substituent to the alpha carbon of the amino acid is an alcohol (CH.sub.2 OH);
• with the proviso that at least 3 amino acids of formula 1 correspond to amino acids present in hirudin (SEQ ID NO:1), or known naturally occurring amino acid sequence variation of hirudin (SEQ ID NO:
• 2;
• SEQ ID NO:3).