Suppression of unimolecular decay of laser desorbed peptide and protein ions by entrainment in rarefied supersonic gas jets under weak electric fields.
← Research streamThe paper describes an ion source design (“MALDI-2”) using an axisymmetric rarefied supersonic gas jet (peak pressure ~100 Pa, flow velocities >300 m/s) under weak electric fields, reporting that rapid collisional cooling in <10 μs provides strong suppression…
Study snapshot
Abstract
Unimolecular decay of sample ions imposes a limit on the usable laser fluence in matrix-assisted laser desorption/ionization (MALDI) ion sources. Traditionally, some modest degree of collisional sample ion cooling has been achieved by connecting MALDI ion sources directly to gas-filled radio frequency (RF) multipoles. It was also discovered in the early 1990s that gas-filled RF multipoles exhibit increased ion transmission efficiency due to collisional ion focusing effects. This unexpected experimental finding was later supported by elementary Monte Carlo simulations. Both experiments and simulations assumed a resting background gas with typical pressures of the order of 1 Pa. However, considerable additional improvements can be achieved if laser desorbed sample ions are introduced immediately after desorption, still within the ion source, in an axisymmetric rarefied supersonic gas jet with peak pressure of the order of 100 Pa and flow velocities >300 m/s, and under weak electric fields. We describe here the design principle and report performance data of an ion source coined "MALDI-2," which incorporates elements of both rarefied aerodynamics and particle optics. Such a design allows superb suppression of metastable fragmentation due to rapid collisional cooling in <10 μs and nearly perfect injection efficiency into the attached RF ion guide, as numerous experiments have confirmed.
AI evidence extraction
Structured fields below were generated from the paper’s abstract and metadata to make the evidence easier to inspect. Automated extraction may be incomplete or incorrect; verify important details against the original paper.
Main findings
The paper describes an ion source design (“MALDI-2”) using an axisymmetric rarefied supersonic gas jet (peak pressure ~100 Pa, flow velocities >300 m/s) under weak electric fields, reporting that rapid collisional cooling in <10 μs provides strong suppression of metastable fragmentation and nearly perfect injection efficiency into an attached RF ion guide, as confirmed by numerous experiments.
Outcomes measured
- Unimolecular decay/metastable fragmentation of laser desorbed peptide and protein ions
- Ion transmission/injection efficiency into RF ion guide
Limitations
- No quantitative performance metrics or numerical results are provided in the abstract
- RF parameters (e.g., frequency, field strength) are not specified
- Study context is an analytical instrument/ion source; no biological or health outcomes described
View raw extracted JSON
{
"study_type": "engineering",
"exposure": {
"band": "RF",
"source": "RF multipoles (ion guide)",
"frequency_mhz": null,
"sar_wkg": null,
"duration": "<10 μs (collisional cooling timescale mentioned)"
},
"population": null,
"sample_size": null,
"outcomes": [
"Unimolecular decay/metastable fragmentation of laser desorbed peptide and protein ions",
"Ion transmission/injection efficiency into RF ion guide"
],
"main_findings": "The paper describes an ion source design (“MALDI-2”) using an axisymmetric rarefied supersonic gas jet (peak pressure ~100 Pa, flow velocities >300 m/s) under weak electric fields, reporting that rapid collisional cooling in <10 μs provides strong suppression of metastable fragmentation and nearly perfect injection efficiency into an attached RF ion guide, as confirmed by numerous experiments.",
"effect_direction": "benefit",
"limitations": [
"No quantitative performance metrics or numerical results are provided in the abstract",
"RF parameters (e.g., frequency, field strength) are not specified",
"Study context is an analytical instrument/ion source; no biological or health outcomes described"
],
"evidence_strength": "insufficient",
"confidence": 0.74,
"peer_reviewed_likely": "yes",
"keywords": [
"MALDI",
"matrix-assisted laser desorption/ionization",
"RF multipoles",
"ion guide",
"supersonic gas jet",
"collisional cooling",
"metastable fragmentation",
"ion transmission efficiency",
"weak electric fields"
],
"suggested_hubs": []
}AI-extracted fields are generated from the abstract and metadata and may be incomplete or incorrect. This material is for informational purposes and is not medical advice.
Identifiers and source
DOI: 10.1063/1.4861040
PubMed: 25669372