Preparative soft and reactive landing of multiply charged protein ions on a plasma-treated metal surface.
Soft landing on a plasma-treated metal surface of multiply protonated protein ions from the gas phase results in a substantial retention of protein function, as demonstrated for trypsin and streptavidin. The majority of trypsin ions soft-landed at hyperthermal kinetic energies are undamaged and retain 72-98% of enzymatic activity after being washed into solution. A small fraction of trypsin ions that were landed at nominal kinetic energies of 130-200 eV remain tethered to the surface and show approximately 50% enzymatic activity. The streptavidin tetramer is found to dissociate to monomer units upon multiple charging in electrospray. The majority of soft-landed monomers can be washed into solution where they show affinity to biotin. The layer of streptavidin monomer that is immobilized on the surface can be detected if fluorescence-tagged and retains the ability to reversibly bind biotin. A mechanism is proposed to explain nondestructive protein ion discharge on the surface that considers proton migration from the soft-landed cations to the metal oxide layer and metal ion reduction by electron transfer from the bulk metal.
Volný
Michael
M
Department of Chemistry, University of Washington, Seattle, Washington 98195, USA.
Elam
W Timothy
WT
Branca
Andrew
A
Ratner
Buddy D
BD
Turecek
Frantisek
F
D001710:Biotin; D007477:Ions / Q000737:chemistry; D008670:Metals / Q000737:chemistry*; D018625:Microscopy, Atomic Force; D008855:Microscopy, Electron, Scanning; D015394:Molecular Structure; D013050:Spectrometry, Fluorescence; D019809:Streptavidin; D014357:Trypsin / Q000032:analysis* / Q000737:chemistry*
D007477:Ions; D008670:Metals; D001710:Biotin; D019809:Streptavidin; D014357:Trypsin