title: Infrared laser desorption and ionization of polypeptides from a polyacrylamide gel.
abstract: We observed direct desorption and ionization of angiotensin II and bovine insulin from a frozen polyacrylamide gel without the addition of an exogenous matrix, using picosecond pulses from a tunable, mid-infrared free-electron laser tuned to strong absorption bands of the gel. At 5.7, 5.9, 6.1 and 6.3 microm we were able to desorb and ionize both analyte molecules, with the strongest analyte signal generated at 5.9 microm. However, no analyte signal was observed at 5.5 microm. Consistent with a previous report, we did not observe ions of either polypeptide at 2.9 microm, in spite of strong overall absorption. We discuss the implications of this wavelength-dependent ionization, including possible ablation mechanisms and energy partitioning between competing vibrational modes.
authors.affiliation: Department of Physics and Astronomy, Vanderbilt University, 6301 Stevenson Center, Nashville, Tennessee 37235, USA.
authors.forename: Michelle
authors.initials: M
authors.lastname: Baltz-Knorr
authors.forename: David R
authors.initials: DR
authors.lastname: Ermer
authors.forename: Kenneth E
authors.initials: KE
authors.lastname: Schriver
authors.forename: Richard F
authors.initials: RF
authors.lastname: Haglund
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry; D000804:Angiotensin II / Q000032:analysis; D000818:Animals; D002417:Cattle; D007259:Infrared Rays; D007328:Insulin / Q000032:analysis; D007834:Lasers; D013058:Mass Spectrometry; D010455:Peptides / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D000099166:Polyacrylamides
chemical_list: D000180:Acrylic Resins; D000804:Angiotensin II; D007328:Insulin; D010455:Peptides; D000099166:Polyacrylamides