The goal of this research is to determine whether a correlation exists between the gas-phase thermodynamic properties of amino acids and their relative signal intensities in MALDI-MS mass spectra. Our group has previously reported a linear correlation between the protonated amino acid peak area over the matrix peak area (ln[AAH+/M+]) as a function of the gas-phase basicity (GB) of the amino acid. This correlation strongly supported a mechanism of analyte ion formation via gas-phase matrix-to-analyte proton transfer. However, this previous study involved the grinding of solid samples together and then affixing these samples to the MALDI target. Since the method of sample preparation could lead to a bias towards gas-phase analyte ion formation, there is a compelling interest to repeat these studies using more conventional MALDI sample preparation approaches, as well as compare the two methods. In initial studies, alanine, isoleucine, valine, and phenylalanine were co-crystallized as well as ground together with the MALDI matrix 4-hydroxy-3,5-dimethoxycinnamic acid (sinapic acid), both individually and in mixtures. This study aims to expand upon initial studies through the use of sinapic acid in a variety of matrix to amino acid molar ratios. Initial results support the proposed proton-transfer ionization process model. Other data have also been extracted, such as the effective temperature of the reaction and trends between the effective temperature of the reaction and the matrix to amino acid mole ratio.

Thermodynamic studies of gas-phase equilibrium in MALDI-MS

255th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.