title: Electrospray-assisted laser desorption ionization mass spectrometry  (ELDI-MS) with an infrared laser for characterizing peptides  and proteins.
abstract: An electrospray-assisted laser desorption/ionization source with an infrared OPO laser (IR-ELDI) was constructed and optimized for peptide and protein mass spectrometry analysis. Similar to ELDI with an ultraviolet laser, IR-ELDI generates multiply charged molecules for peptides and proteins measured under ambient sampling conditions. Both samples in the dried state and analyte solutions can be directly measured by IR-ELDI without the presence of a conventional MALDI matrix. However, the analysis of sample solutions is shown to greatly enhance the sensitivity of the mass spectrometry measurement, as a 100-fold sensitivity gain for peptide measurements was measured. The limit of detection of IR-ELDI was determined to be 250 fmol for bradykinin (1.1 kDa), 100 fmol for ubiquitin (8.6 kDa), and 500 fmol for carbonic anhydrase (29 kDa). IR-ELDI is amenable for MS and MSn analysis for proteins up to 80 kDa transferrin. IR-ELDI-MS may be a useful tool for protein sequencing analysis from complex biological matrices, with minimal sample preparation required.
authors.affiliation: Department of Chemistry and Biochemistry, University of California-Los Angeles, Los Angeles, CA 90095, USA.
authors.forename: Ivory X
authors.initials: IX
authors.lastname: Peng
authors.forename: Rachel R
authors.initials: RR
authors.lastname: Ogorzalek Loo
authors.forename: Eli
authors.initials: E
authors.lastname: Margalith
authors.forename: Mark W
authors.initials: MW
authors.lastname: Little
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Loo
mesh_terms: D001920:Bradykinin / Q000737:chemistry; D002256:Carbonic Anhydrases / Q000737:chemistry; D007834:Lasers; D010455:Peptides / Q000737:chemistry*; D011506:Proteins / Q000737:chemistry*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000295:instrumentation / Q000379:methods*; D025801:Ubiquitin / Q000737:chemistry
chemical_list: D010455:Peptides; D011506:Proteins; D025801:Ubiquitin; D002256:Carbonic Anhydrases; D001920:Bradykinin