Silver as a cationizing agent in the identification of amino acids by the MALDI-MS method

Abstract

A systematic study of the ionization of amino acids by the MALDI method was carried out. One of the important areas of research in modern science is the study of physicochemical processes during ionization in various ways A Bruker Ultraflex mass spectrometer (Bruker, Germany) equipped with a nitrogen laser (λ=337 nm) was used to study the cluster formation. To increase the efficiency of ionization and information content of mass spectra, silver halides were synthesized in aqueous solutions by mixing solutions of silver nitrate and the corresponding potassium halide. Amino acids were applied to the surface of stainless steel from a water-acetonitrile solution. In the mass spectrum, a wide range of different cluster ions of silver chloride is seen and the first clusters with a charged center on the cluster Ag3. Threonine can be identified by an adduct with silver having an intensity of peaks of about 5000 abs. units and the signal-to-noise ratio is more than 500, which is 1.5 orders of magnitude better than for ionization without the use of silver chloride. It is shown that the production of high-intensity peaks of amino acids only with the use of highly developed surfaces, for example, carbon blacks of various types in this method is possible. For more effective cationization of amino acids, it has been proposed to use silver ions for ionization. It was shown that high-intensity peaks of amino-cationized silver are formed by this method. In addition, it was shown that silver chloride ionizing amino acids serves as a matrix and stabilizes large cluster agglomerates of amino acids in plasma above the surface of stainless steel.