Internal energies of analyte ions generated from different matrix-assistedlaser desorption/ionization matrices

A. transfer of energy into the internal modes of the matrix and analyte is expected to occur during matrix-assisted laser desorption/ioniziation (MALD I) processes. Both the physical and thermochemical properties of the MALDI matrix used can influence the ion internal energy and analyte ion fragmenta tion. Here we report the effect of several MALDI matrices on the relative i nternal energy of the 2'-deoxyadenylyl-(3',5')-2'-deoxyguanosine (AG) anion . Relative internal energies mere probed by low-energy collision-induced di ssociation in a Fourier transform ion cyclotron resonance mass spectrometer . Sublimation temperatures of the matrices under study were also determined and found to lie between 409 and 455 K. Analyte ion internal and initial k inetic energies did not correlate with matrix sublimation temperatures. In contrast, a strong correlation between the relative internal energy of the analyte anions and the gas-phase basicity of the matrix anions was found, T hese results suggest that gas-phase proton transfer reactions play an impor tant role in MALDI analyte ion formation and influence their internal energ y and fragmentation behavior. Copyright (C) 2000 John Wiley & Sons, Ltd.