Dataset Information

Matrix-assisted laser desorption/ionization high-energy collision-induced dissociation of steroids: analysis of oxysterols in rat brain.

ABSTRACT: Neutral steroids have traditionally been analyzed by gas chromatography/mass spectrometry (GC/MS) after necessary derivatization reactions. However, GC/MS is unsuitable for the analysis of many conjugated steroids and those with unsuspected functional groups. Here we describe an alternative analytical method specifically designed for the analysis of oxosteroids and those with a 3beta-hydroxy-delta5 or 5alpha-hydrogen-3beta-hydroxy structure. Steroids were derivatized with Girard P (GP) hydrazine to give GP hydrazones, which are charged species and readily analyzed by matrix-assisted laser desorption/ionization mass spectrometry. The resulting [M]+ ions were then subjected to high-energy collision-induced dissociation on a tandem time-of-flight instrument. The product ion spectra give structurally informative fragment ion patterns. The sensitivity of the analytical method is such that steroid structures can be determined from low-picogram (low-femtomole) amounts of sample. The utility of the method has been demonstrated by the analysis of oxysterols extracted from rat brain.

SUBMITTER: Wang Y

PROVIDER: S-EPMC2315783 | biostudies-literature | 2006 Jan

REPOSITORIES: biostudies-literature

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Matrix-assisted laser desorption/ionization high-energy collision-induced dissociation of steroids: analysis of oxysterols in rat brain.

Wang Yuqin Y Hornshaw Martin M Alvelius Gunvor G Bodin Karl K Liu Suya S Sjövall Jan J Griffiths William J WJ

Analytical chemistry 20060101 1

Neutral steroids have traditionally been analyzed by gas chromatography/mass spectrometry (GC/MS) after necessary derivatization reactions. However, GC/MS is unsuitable for the analysis of many conjugated steroids and those with unsuspected functional groups. Here we describe an alternative analytical method specifically designed for the analysis of oxosteroids and those with a 3beta-hydroxy-delta5 or 5alpha-hydrogen-3beta-hydroxy structure. Steroids were derivatized with Girard P (GP) hydrazine ...[more]

PMID: 16383324

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Project description:RationaleUnderstanding the mechanisms of matrix-assisted laser desorption/ionization (MALDI) promises improvements in the sensitivity and specificity of many established applications in the field of mass spectrometry. This paper reports a serendipitous observation of a significant ion yield in a post-ionization experiment conducted after the sample had been removed from a standard atmospheric pressure (AP)-MALDI source. This post-ionization is interpreted in terms of collisions of microparticles moving with a hypersonic velocity into a solid surface. Calculations show that the thermal energy released during such collisions is close to that absorbed by the top matrix layer in traditional MALDI. The microparticles, containing both the matrix and analytes, could be detached from a film produced inside the inlet capillary during the sample ablation and accelerated by the flow rushing through the capillary. These observations contribute some new perspective to ion formation in both laser and laser-less matrix-assisted ionization.MethodsAn AP-MALDI ion source hyphenated with a three-stage high-pressure ion funnel system was utilized for peptide mass analysis. After the laser had been turned off and the MALDI sample removed, ions were detected during a gradual reduction of the background pressure in the first funnel. The constant-rate pressure reduction led to the reproducible appearance of different singly and doubly charged peptide peaks in mass spectra taken a few seconds after the end of the MALDI analysis of a dried-droplet spot.ResultsThe ion yield as well as the mass range of ions observed with a significant delay after a completion of the primary MALDI analysis depended primarily on the background pressure inside the first funnel. The production of ions in this post-ionization step was exclusively observed during the pressure drop. A lower matrix background and significant increase in relative yield of double-protonated ions are reported.ConclusionsThe observations were partially consistent with a model of the supersonic jet from the inlet capillary accelerating detached particles to kinetic energies suitable for matrix-assisted hypersonic-velocity impact ionization.

Dataset Information

Matrix-assisted laser desorption/ionization high-energy collision-induced dissociation of steroids: analysis of oxysterols in rat brain.

Publications

Matrix-assisted laser desorption/ionization high-energy collision-induced dissociation of steroids: analysis of oxysterols in rat brain.

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