SAMPLE EXPOSURE EFFECTS IN MATRIX-ASSISTED LASER-DESORPTION IONIZATION MASS-SPECTROMETRY OF LARGE BIOMOLECULES

Effects of sample exposure to UV laser irradiation on the matrix-assis ted laser desorption-ionization (MALDI) mass spectra of different prot eins are reported. The exposure is varied by irradiating the same samp le spot with a differing number of UV laser pulses. The ion yield, mas s resolution and internal energy content of ejected molecular ions are monitored as a function of the sample exposure. Other parameters that influence the MALDI spectra (and related to sample exposure) such as laser fluence, sample thickness, matrix-to-protein molar ratio, total deposited amount, and molecular mass of the protein, are also examined .