title: Optical detection and charge-state analysis of MALDI-generated particles with molecular masses larger than 5 MDa.
abstract: Charged polystyrene nanoparticles are generated by matrix-assisted laser desorption/ionization (MALDI) and detected by laser-induced fluorescence (LIF) in a quadrupole ion trap. Employing the LIF technique, observations of individual fluorescent nanospheres (27 nm in diameter and containing 180 fluorescein dye equivalents) have been achieved with an average signal-to-noise ratio of approximately 10. With the trap operating at a frequency around 5 kHz, charge state analysis of the particles reveals that the number of charges carried by the spheres is between 1 and 10. It suggests a mass-to-charge ratio (m/z) in the range of 10(5)-10(6) for the MALDI-generated particles. To effectively trap such large particles (m > 5 MDa), damping of the particles' motions by using approximately 50 mTorr He buffer gas is absolutely required. Similar findings are obtained for particles with a nominal size of 1 microm in diameter, demonstrating that production of charged particles with a molecular mass as high as 10(12) Da is possible using the MALDI technique.
authors.affiliation: Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan.
authors.forename: Y
authors.initials: Y
authors.lastname: Cai
authors.forename: W P
authors.initials: WP
authors.lastname: Peng
authors.forename: S J
authors.initials: SJ
authors.lastname: Kuo
authors.forename: S
authors.initials: S
authors.lastname: Sabu
authors.forename: C C
authors.initials: CC
authors.lastname: Han
authors.forename: H C
authors.initials: HC
authors.lastname: Chang
mesh_terms: D005456:Fluorescent Dyes; D005470:Fluorometry; D008863:Microspheres; D015336:Molecular Probe Techniques; D008970:Molecular Weight; D036103:Nanotechnology / Q000379:methods; D010316:Particle Size; D011137:Polystyrenes; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*
chemical_list: D005456:Fluorescent Dyes; D011137:Polystyrenes