title: Charge state coalescence during electrospray ionization improves peptide identification by tandem mass spectrometry.
abstract: We report the effects of supercharging reagents dimethyl sulphoxide (DMSO) and m-nitrobenzyl alcohol (m-NBA) applied to untargeted peptide identification, with special emphasis on non-tryptic peptides. Peptides generated from a mixture of five standard proteins digested with trypsin, elastase, or pepsin were separated with nanoflow liquid chromatography using mobile phases modified with either 5% DMSO or 0.1%m-NBA. Eluting peptides were ionized by online electrospray and sequenced by both CID and ETD using data-dependent MS/MS. Statistically significant improvements in peptide identifications were observed with DMSO co-solvent. In order to understand this observation, we assessed the effects of supercharging reagents on the chromatographic separation and the electrospray quality. The increase in identifications was not due to supercharging, which was greater for the 0.1%m-NBA co-solvent and not observed for the 5.0% DMSO co-solvent. The improved MS/MS efficiency using the DMSO modified mobile phase appeared to result from charge state coalescence.
authors.affiliation: Department of Chemistry and Biochemistry, University of California-San Diego, La Jolla, CA, 92093-0378, USA.
authors.forename: Jesse G
authors.initials: JG
authors.lastname: Meyer
authors.forename: Elizabeth
authors.initials: E
authors.lastname: A Komives
mesh_terms: D000595:Amino Acid Sequence; D001592:Benzyl Alcohols / Q000737:chemistry; D004121:Dimethyl Sulfoxide / Q000737:chemistry; D008969:Molecular Sequence Data; D010196:Pancreatic Elastase / Q000737:chemistry; D010434:Pepsin A / Q000737:chemistry; D010446:Peptide Fragments / Q000737:chemistry*; D011506:Proteins / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D053719:Tandem Mass Spectrometry / Q000379:methods*; D014357:Trypsin / Q000737:chemistry
chemical_list: D001592:Benzyl Alcohols; D010446:Peptide Fragments; D011506:Proteins; D010196:Pancreatic Elastase; D014357:Trypsin; D010434:Pepsin A; C046886:3-nitrobenzyl alcohol; D004121:Dimethyl Sulfoxide