ATTOMOLE BIOMOLECULE MASS ANALYSIS BY MATRIX-ASSISTED LASER-DESORPTION IONIZATION FOURIER-TRANSFORM ION-CYCLOTRON RESONANCE

Significantly improved sensitivity for analysis of biomolecules by MAL DI FT-ICR mass spectrometry is achieved by (i) microscope monitored sa mple deposition onto a small indentation on the probe tip and (ii) mul tiple remeasurement of ions from a single laser shot. A simple modific ation to the solids probe tip allows for microdeposition of a few amol s of analyte onto small indentation spots previously aligned with the laser beam. Ion multiple remeasurement of the same ion packet enhances the signal-to-noise ratio and thus extends the achievable FT-ICR MS d etection limit. We demonstrate that FT-ICR can be used to detect paren t and structurally significant fragment ions of peptides and phospholi pids at low amol amounts. Positive ion mass spectra for similar to 90 amol of a mixture of angiotensin II and bradykinin, similar to 40 amol of dipalmitoylglycerophosphatidylcholine, and similar to 8 amol of su bstance P constitute the lowest reported detection limits to date for FT-ICR mass analysis of MALDI-generated ions.