Time-Resolved Micro Liquid Desorption Mass Spectrometry: Mechanism, Features, and Kinetic Applications*

Ales Charvat; Andreas Bögehold; Bernd Abel

doi:10.1071/CH05249

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Time-Resolved Micro Liquid Desorption Mass Spectrometry: Mechanism, Features, and Kinetic Applications*

Ales Charvat ^A ^B , Andreas Bögehold ^A ^B and Bernd Abel ^A ^B ^C

+ Author Affiliations

- Author Affiliations

^A Institut für Physikalische Chemie der Universität Göttingen, 37077 Göttingen, Germany.

^B Max Planck Institut für biophysikalische Chemie, 37077 Göttingen, Germany.

^C Corresponding author. Email: babel@gwdg.de

Bernd Abel studied chemistry in Göttingen, graduating in 1990, then spent two years at the Massachusetts Institute of Technology in Boston, USA. At present, he is an associated professor (apl) in the Institute for Physical Chemistry of the Georg August University and group leader at the Max Planck Institute for Biophysical Chemistry in Göttingen. His current interests and research projects are in the field of time-resolved (bio)molecular kinetics, dynamics, and analytics in complex systems. He is author of about 80 research papers and he recently received the Nernstâ€“Haberâ€“Bodenstein Prize of the German Bunsen Society.

Ales Charvat studied physics in Prague, and graduated in applied physics and spectroscopy in Grenoble (France) in 1994. At present he is a research associate at the Max Planck Institute for Biophysical Chemistry. His interests are in the fields of spectroscopy and mass spectrometry. He and Bernd Abel recently received the Sir Harold Thompson Memorial Award (Elsevier Science).

Andreas Bögehold studied chemistry in GÃ¶ttingen and he finished his diploma in 2005 under the supervision of Bernd Abel in the field of analytical mass spectrometry. Currently he is graduate student in the Abel research group and works on time-resolved liquid beam desorption mass spectrometry. His main field of research is the investigation of protein aggregation of amyloid systems. He is currently also member of the Physical Chemistry Graduate School 782 in Göttingen.

Australian Journal of Chemistry 59(2) 81-103 https://doi.org/10.1071/CH05249
Submitted: 29 August 2005 Accepted: 5 January 2006 Published: 7 March 2006

Abstract

Liquid water beam desorption mass spectrometry is an intriguing technique to isolate charged molecular aggregates directly from the liquid phase and to analyze them employing sensitive mass spectrometry. The liquid phase in this approach consists of a 10 µm diameter free liquid filament in vacuum which is irradiated by a focussed infrared laser pulse resonant with the OH-stretch vibration of bulk water. Depending upon the laser wavelength, charged (e.g. protonated) macromolecules are isolated from solution through a still poorly characterized mechanism. After the gentle liquid-to-vacuum transfer the low-charge-state aggregates are analyzed using time-of-flight mass spectrometry. A recent variant of the technique uses high performance liquid chromatography valves for local liquid injections of samples in the liquid carrier beam, which enables very low sample consumption and high speed sample analysis.

In this review we summarize recent work to characterize the ‘desorption’ or ion isolation mechanism in this type of experiment. A decisive and interesting feature of micro liquid beam desorption mass spectrometry is that — under certain conditions — the gas-phase mass signal for a large number of small as well as supramolecular systems displays a surprisingly linear response on the solution concentration over many orders of magnitude, even for mixtures and complex body fluids. This feature and the all-liquid state nature of the technique makes this technique a solution-type spectroscopy that enables real kinetic studies involving (bio)polymers in solution without the need for internal standards. Two applications of the technique monitoring enzyme digestion of proteins and protein aggregation of an amyloid model system are highlighted, both displaying its potential for monitoring biokinetics in solution.

Acknowledgments

This work was supported by the Deutsche Forschungsgemeinschaft (DFG) within the Graduiertenkolleg 782 (‘Spectroscopy and dynamics of molecular coils and aggregates’) and the Sonderforschungsbereich 357, the Max Planck Society, as well as the Ministry of Trade and Commerce of Lower Saxony (‘Development of Multidimensional Analytical Techniques for Proteomics’, Verbundprojekt Nr. 80008452). Helpful discussions of several aspects of the present work with Prof. Franz Hillenkamp, Dr Manfred Faubel, Dr Jürgen Niemeyer, Dr Boleslaw Stasicki, and Dr Thomas Jovin are gratefully acknowledged. The authors also thank the Jovin group at the MPI für biophysikalische Chemie for the AFM measurements on insulin fibrils.

References

^* Dedicated to Prof. Jürgen Troe on the occasion of his 65th birthday.

Time-Resolved Micro Liquid Desorption Mass Spectrometry: Mechanism, Features, and Kinetic Applications*

Abstract

Acknowledgments

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