The invention provides compounds of Formula (I):OP-Peptide-Linker-CP (I)whereinOP is selected from the group consisting of reactiveorganophosphorus reagents, nerve agents and pesticides, wherein P is Spstereoisomer, Rpstereoisomer, or mixture thereof;R and R' are as defined in the description;X is oxygen, sulfur, selenium or imino;Peptide is a sequence of amino acids containing a serine, threonine ortyrosineto which an OP is attached, wherein a total number of amino acids is between 7and 41;Linker is an amino acid or other bifunctional reagent capable of covalentlylinking OP-peptide to a CP;CP is a conjugate protein used to display haptens for antibody generation; andsalts thereof.