Even with chemical protein modification, which is considered to have a relatively broad substrate tolerance, subtle differences in reaction scale, temperature, and isoelectric points (PIs) can drastically affect conversion . In general, enzymes have a narrow substrate tolerance, so it is expected that differences in protein properties could have a profound effect on reactivity. Based on previous reports , we aimed to explore the applicability of the LplA-based antibody modification method to a broader range of proteins. Our investigation focused on proteins with varying molecular weights and PI (Table ). This approach would determine if the reaction conditions of the LplA method are versatile across different protein characteristics. In present study, the modification of each protein by LplA with azido-octanoic acid was achieved by a method previously documented in the literature. We chose an extended reaction time Lysozyme (Egg-derived), Lane-6: hLysozyme, Lane-7: BLG, Lane-8: Transferrin.