We do not use a single bi-functional linker like SMCC. Our linking chemistry links through the e-amino group on the lysine, or through a thiol group on a cysteine allowing for direct modification of your peptide after synthesis. We also have a peptide reagent that adds our S-Hynic linker onto either end of the peptide during synthesis. Our chemistry then requires a separate modification of the antibody/protein with a traceable linker that corresponds to S-Hynic. This linker is S-4FB. The resulting conjugate that forms when the two linkers come together has a hydrazone chromaphore that allows the end-user to know exactly how many peptides are on the antibody. This chemistry provides several advantages when compared to SMCC; namely, it is more reproducible, it is traceable, and it reacts specifically, preventing undesirable polymer formation.