STRUCTURAL MASS-SPECTROMETRY OF MATRIX-ASSISTED LASER-DESORBED BIOMOLECULES BY FOURIER-TRANSFORM ION-CYCLOTRON RESONANCE MASS-SPECTROMETRY - PHOTOIONIZATION AND PHOTOFRAGMENTATION

Laser desorption ionization of compounds that absorb 337 nm (e.g., vitamin B12 and selected porphyrins) are examined by using Fourier transform ion cyclotron resonance (FTICR) mass spectrometry. The experiments are performed by mixing the sample with a host compound that promotes desorption and/or ionization. The relative abundance of photofragment ions can be controlled by simple adjustments of parameters such as the laser power and matrix-to-analyte ratio. In addition, it is shown that gas-phase photoionization/photodissociation of laser-desorbed species by a second laser pulse provides structural information for both negative and positive ions.