A SELF-ASSEMBLED MATRIX MONOLAYER FOR UV-MALDI MASS-SPECTROMETRY

Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry has in recent years significantly advanced the field of polymer analys is. However, the mechanisms of the desorption and ionization processes , and in particular the critical role played by the matrix, remain unc lear. In the present work, the usual matrix is replaced with a self-as sembled monolayer consisting of a UV absorbing matrix-like compound co valently linked to a gold surface. Analytes such as proteins or oligon ucleotides are directly deposited on the covalently modified probe tip s and mass analyzed by laser desorption time of flight (TOF) mass spec trometry. Several types of monolayers were investigated and tested for their ability to produce positive and negative analyte ions. Molecula r ion signals were obtained for dT(10) oligonucleotides and proteins a s large as cytochrome C on monolayers of methyl N-(4-mercaptophenyl)ca rbamate (MMPC). The amenability of this model system to characterizati on with established physical and chemical methods should help investig ate the processes involved in MALDI.