The invention concerns a conjugate of formula A-X-B, wherein:- A is a peptide tag molecule of known molecular weight,- X is a linker that is cleaved during sample desorption/ionization, and- B is an antibody that binds specifically to said target molecule,and wherein said conjugate is of formula:The invention also relates to a method for determining at least one target peptide, protein, antigen or hapten map in a tissue section, comprising the use of the conjugate.
