title: Introduction of a 20 kHz Nd:YVO4 laser into a hybrid quadrupole time-of-flight mass spectrometer for MALDI-MS imaging.
abstract: A commercial hybrid quadrupole time-of-flight mass spectrometer has been modified for high-speed matrix-assisted laser desorption ionisation (MALDI) imaging using a short-pulse optical technology Nd:YVO(4) laser. The laser operating in frequency-tripled mode (lambda = 355 nm) is capable of delivering 1.5-ns pulses of energy at up to 8 microJ at 5-10 kHz and 3 microJ at 20 kHz. Experiments to improve beam homogeneity and reduce laser speckle by mechanical vibration of the fibre-optic laser delivery system are reported along with data from trial and tissue imaging experiments using the modified instrument. The laser appeared to yield best results for MALDI-MS imaging experiments when operating at repetition rates 5-10 kHz. Combining this with raster imaging allowed images of rat brain sections to be recorded in 37 min. Similarly, images of the distribution of peptides in "on-tissue" digest experiments from tumour tissues were recorded in 1 h and 30 min rather than the 8-h acquisition time previously used. A brief investigation of targeted protein analysis/imaging by multiple reaction monitoring experiments "on-tissue" is reported. A total of 26 transitions were recorded over a 3-s cycle time and images of abundant proteins were successfully recorded.
authors.affiliation: Biomedical Research Centre, Sheffield Hallam University, Howard Street, Sheffield S1 1WB, UK.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Trim
authors.forename: Marie-Claude
authors.initials: MC
authors.lastname: Djidja
authors.forename: Sally J
authors.initials: SJ
authors.lastname: Atkinson
authors.forename: Keith
authors.initials: K
authors.lastname: Oakes
authors.forename: Laura M
authors.initials: LM
authors.lastname: Cole
authors.forename: David M G
authors.initials: DM
authors.lastname: Anderson
authors.forename: Philippa J
authors.initials: PJ
authors.lastname: Hart
authors.forename: Simona
authors.initials: S
authors.lastname: Francese
authors.forename: Malcolm R
authors.initials: MR
authors.lastname: Clench
mesh_terms: D000818:Animals; D001923:Brain Chemistry; D006801:Humans; D007834:Lasers; D008297:Male; D009369:Neoplasms / Q000737:chemistry; D011506:Proteins / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000295:instrumentation*
chemical_list: D011506:Proteins