SYNTHETIC PEPTIDE AND ANTIBODY THERETO

The synthetic peptides have amino-acid sequences which correspond in whole or in part to the amino-acid sequence of prothrombin and are antigenic, and they are used for immunising an animal and for purifying specific antibodies, and the antibodies against these peptides are used to determine the F2/F1+2 fragments. Hitherto used for the determination of the contents of the F2/F1+2 fragments have been antibodies induced by immunisation with natural, highly purified prothrombin F2/F1+2 fragments. The isolation of these prothrombin fragments is elaborate and costly, and the antibodies raised therewith show cross-reactions with intact prothrombin. Used for the immunisation according to the invention are synthetic peptides which have amino-acid sequences which correspond in whole or in part to the amino-acid sequence of prothrombin and are antigenic. The resulting antibodies react specifically with the antigen to be used for immunisation; if the peptides contain the carboxy-terminal amino-acid sequence of the F2/F1+2 fragments resulting after cleavage of the prothrombin molecule with factor Xa, the antibodies which are raised react specifically with the F2/F1+2 fragments but not with intact native prothrombin so that it is possible to obtain information about the degree of activation of prothrombin.