Fig. 4. (a) Cell surface modification reaction by Ru1-catalyzed alkylation using benzyl fluoride substrate (Ru/BnF). (b) Model reaction of Ru/BnF with HSA analyzed by SDS-PAGE: protein ladder (lane 1), HSA (lane 2), after reaction of Au1/TAMRA-PE (lanes 3–4) or Ru1/TAMRA-BnF (lanes 5–6). (c) The modified amino acids on HSA-TAMRA (lane 6 in b), as determined by the MS/MS analysis. The ribbon diagram of HSA (PDB: 1AO6) and tagged amino acids are colored in green and red, respectively. (d) Plausible modified structure of amino acids.