Differential Protein Labeling based on Electrochemically
Generated Reactive Intermediates
Lars Büter, Helene Faber, Tina Wigger and Uwe Karst
Institute of Inorganic and Analytical Chemistry, University of Münster, Corrensstr.
28/30, 48149 Münster, lars.bueter@uni-muenster.de
Electrochemical generation of quinoid intermediates via dehydrogenation leads to
a Micheal-type addition of these electrophilic structures to nucleophilic
compounds. Therefore, modification of peptides and proteins that contain the
amino acid cysteine can be easily achieved due to the nucleophilic nature of their
free thiol groups. In this poster, we present an approach for the electrochemical
generation of reactive benzoquinone intermediates of phenol in its native and
isotope labeled form (13C6-phenol). Subsequent reaction with peptides and
proteins results in a defined mass shift between the differentially labeled
biomolecules.
The hyphenation of an electrochemical cell to electrospray ionization mass
spectrometry enables the immediate detection of generated peptide adducts. By
applying a potential ramp, the optimum potential for the generation of reactive
intermediates can be determined. An extension of the instrumental set-up by
means of liquid chromatography allows the online generation, separation and
identification of modified proteins. Furthermore, after tryptic digestion, the binding
position in the proteins can be determined and a mass shift can be observed,
which can be traced back to the heavier, labeled species phenol. Hence, the
identification of these tryptic peptides is simplified, thus allowing the identification
of proteins in a complex mixture.