title: Preparative soft and reactive landing of multiply charged protein ions on a plasma-treated metal surface.
abstract: 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.
authors.affiliation: Department of Chemistry, University of Washington, Seattle, Washington 98195, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Volný
authors.forename: W Timothy
authors.initials: WT
authors.lastname: Elam
authors.forename: Andrew
authors.initials: A
authors.lastname: Branca
authors.forename: Buddy D
authors.initials: BD
authors.lastname: Ratner
authors.forename: Frantisek
authors.initials: F
authors.lastname: Turecek
mesh_terms: 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*
chemical_list: D007477:Ions; D008670:Metals; D001710:Biotin; D019809:Streptavidin; D014357:Trypsin