Abstract: Disclosed are chromogenic or fluorogenic peptide-type compounds adapted for use in determining endotoxin in a sample by a Limulus amebocyte lysate-type assay. The compounds have the general formula:R.sub.1 --A.sub.1 --A.sub.2 --A.sub.3 --A.sub.4 --B--R.sub.2wherein R.sub.1 represents hydrogen, a blocking aromatic hydrocarbon or acyl; A.sub.1 represents an L or D-amino acid selected from either Ileu, Val or Leu; A.sub.2 represents Glu or Asp; A.sub.3 represents Ala or Cyst; A.sub.4 represents Arg, B represents a linkage group selected from ester and amide linkage groups; and R.sub.2 represents a chromogenic or fluorogenic group which is covalently attached to the C-carboxyl terminal of arginine through the B linkage group and which yields a chromophoric or fluorescent marker compound of the formula R.sub.2 --B--H upon enzymatic hydrolysis from the remainder of the peptide-type compound by activated LAL pro-clot enzyme.

Abstract: Disclosed are chromogenic or fluorogenic peptide-type compounds adapted for use in determining endotoxin in a sample by a Limulus amebocyte lysate-type assay. The compounds have the general formula:R.sub.1 -A.sub.1 -A.sub.2 -A.sub.3 -A.sub.4 -B-R.sub.2wherein R.sub.1 represents hydrogen, a blocking aromatic hydrocarbon or acyl; A.sub.1 represents an L or D-amino acid selected from either Ileu, Val or Leu; A.sub.2 represents Glu or Asp; A.sub.3 represents Ala or Cyst; A.sub.4 represents Arg, B represents a linkage group selected from ester and amide linkage groups; and R.sub.2 represents a chromogenic or fluorogenic group which is covalently attached to the C-carboxyl terminal of arginine through the B linkage group and which yields a chromophoric or fluorescent marker compound of the formula R.sub.2 -B-H upon enzymatic hydrolysis from the remainder of the peptide-type compound by activated LAL pro-clot enzyme.