Victor V. Laiko

Recent developments in atmospheric pressure MALDI mass spectrometry

Abstract A new atmospheric pressure (AP) matrix-assisted laser desorption/ionization (MALDI) ion source that includes an extended capillary for delivery of AP-MALDI ions toward a mass spectrometer (MS) atmospheric pressure interface inlet aperture, an optical fiber for laser energy transfer to a target, and x – y travel stages for high throughput analysis of multiple samples, is described. The new source has been interfaced with a Thermo Finnigan LCQ ion trap mass spectrometer bringing powerful high throughput tandem MS capabilities to MALDI analysis. The resulting AP-MALDI-LCQ instrument demonstrated an absolute sensitivity in the low femtomole range for simple peptide mixture analysis, a mass range up to 2000–4000 (limited by LCQ), and an extensive fragmentation of singly-charged AP-MALDI ions in MS/MS experiments. The potential strength of this technique has been illustrated by numerous applications ranging from fragile molecule analysis to tryptic digest analysis for protein identification.

Desorption/ionization of biomolecules from aqueous solutions at atmospheric pressure using an infrared laser at 3 μm

A new atmospheric pressure (AP) infrared (IR) matrix-assisted laser desorption/ionization (MALDI) ion source was developed and interfaced with a Thermo Finnigan LCQ ion trap mass spectrometer. The source utilized a miniature all-solid-state optical parametric oscillator (OPO)-based IR laser system tunable in the λ = 1.5–4 μm spectral range and a nitrogen ultraviolet (UV) laser (λ = 337 nm) for use in comparative studies. The system demonstrated comparable performance at 3 μm and 337 ran wavelengths if UV matrices were used. However, AP IR-MALDI using a 3 μm wavelength showed good performance with a much broader choice of matrices including glycerol and liquid water. AP IR-MALDI mass spectra of peptides in the mass range up to 2000 Da were obtained directly from aqueous solutions at atmospheric conditions for the first time. A potential use of the new AP IR-MALDI ion source includes direct MS analysis of biological cells and tissues in a normal atmospheric environment as well as on-line coupling of mass spectrometers with liquid separation techniques.

Atmospheric pressure matrix-assisted laser desorption/ionization (AP MALDI) on a quadrupole ion trap mass spectrometer

Abstract A new atmospheric pressure ionization technique, atmospheric pressure matrix-assisted laser desorption/ionization (AP MALDI), was recently introduced by Laiko et al. [U.S. Patent 5,965,884; Abstracts of the 4th International Symposium on Mass Spectrometry in the Health and Life Sciences, San Francisco, CA, 25–29 August 1998; Atmospheric Pressure Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry, Proceedings of the 47th ASMS Conference on Mass Spectrometry and Allied Topics, Dallas, TX, 1999; Anal. Chem. 72 (2000) 652]. This source has been coupled to an orthogonal time-of-flight mass spectrometer [U.S. Patent 5,965,884; Abstracts of the 4th International Symposium on Mass Spectrometry in the Health and Life Sciences, San Francisco, CA, 25–29 August 1998; Atmospheric Pressure Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry, Proceedings of the 47th ASMS Conference on Mass Spectrometry and Allied Topics, Dallas, TX, 1999; Anal. Chem. 72 (2000) 652] and to an ion trap mass spectrometer (ITMS) [Anal. Chem. 72 (2000) 5239; Atmospheric Pressure MALDI/Ion Trap Mass Spectrometry, Proceedings of the 48th ASMS Conference on Mass Spectrometry and Allied Topics, Long Beach, CA, June 2000; An Atmospheric Pressure MALDI Probe for Use with ESI Source Interfaces, Proceedings of the 48th ASMS Conference on Mass Spectrometry and Allied Topics, Long Beach, CA, June 2000; Atmospheric Pressure Matrix-Assisted Laser Desorption Ionization, Proceedings of the 48th ASMS Conference on Mass Spectrometry and Allied Topics, Long Beach, CA, June 2000]. Here, we present the current status of the work involving the development of an AP MALDI source for an ITMS. In addition, we present recent work from our own laboratory to demonstrate the utility of this novel configuration.

Orthogonal Extraction Ion Mobility Spectrometry

Ion Mobility Spectrometry is a powerful tool for the study of molecular conformations, separation of mass isomers, and analysis of complex mixtures and suppression of chemical background. The factors that limit the capabilities of the technique include its relatively low resolving power and duty cycle. New principle of gas-phase ion separation, based on ion focusing under the influence of electrostatic field and stationary in time gas flow, is proposed. Both analytical calculations and a numerical simulation show that a diffusion-limited resolution of several hundred can be achieved. The new type of ion mobility analyzer is called orthogonal extraction IMS. The proposed ortho-IMS can be interfaced with commercial mass spectrometers and offers the theoretical resolution of several hundred and ion transmission close to 100%.