Abstract: The invention relates to a novel labeling reactant, suitable for labeling of a biospecific binding reactant using solid-phase synthesis. The invention further concerns new labeling methods. The novel labeling reactant has the formula (I) ##STR1## wherein -A- is a bivalent aromatic structure capable of absorbing light or energy and transferring the excitation energy to a lanthanide ion after the product made by the said solid-phase synthesis has been released from the used solid support, deprotected and converted to a lanthanide chelate;-G- is a bridge replacing a hydrogen atom in A;R is a protected amino acid residue --CH(NHX)COOH, where X is a transient protecting group, or its active ester, where said ester is e.g. an N-hydroxysuccinimido, p-nitrophenol or pentafluorophenol ester; andR' is --COOR'" where R'" is an alkyl of 1 to 4 carbon atoms, phenyl or benzyl, which phenyl or benzyl can be substituted or unsubstituted.

Abstract: Compound having the following structure: ##STR1## R is a direct chain or branched alkylene group comprising 2-8 carbon atoms,n and m are 0 or 1,Y is a carboxylic or phosphonic acid, andX is an active functional group which permits covalent coupling to a bio-organic molecule.