In an embodiment of the invention, a composition for treating a cell population comprises an Affinity Medicant Conjugate (AMC). The medicant moiety can be a toxin including an acylfulvene or a drug moiety. The affinity moiety can be an antibody, a binding protein, a steroid, a lipid, a growth factor, a protein, a peptide or non peptidic. The affinity moiety can be covalently bound to the medicant via a linker. Novel linkers that can be directed to cysteine, arginine or lysine residues based on solution pH allow greater flexibility in preserving and/or generating specific epitopes in the AMC.