Matrix-assisted laser desorption/ ionization (MALDI) mass spectrometry imaging (MSI) is an important technique that predominantly produces singly charged ions. The ability to generate multiply charged ions can enhance fragmentation in tandem mass spectrometry experiments and thereby improve compound identification. The matrix compound 2-nitrophloroglucinol (2-NPG) has been shown to produce multiply charged ions from proteins and other biomolecules both by inlet ionization and by MALDI. The goal of this project is to develop new matrix systems capable of producing multiply charged ions for MALDI MSI under high vacuum. Consecutive rat brain tissue sections of 10 µm thickness were deposited on conductive microscope slides, washed, dried, and a matrix solution spiked with analyte was applied. Mass spectra were obtained using a Bruker Ultraflextreme time-of-flight mass spectrometer. Multiply charged proteins up to +8 were detected for cytochrome C and myoglobin; however, it was difficult to obtain high charge states for the native proteins. To increase the available surface area for matrix and analyte co-crystallization, nanoparticles were introduced. Silica particles with diameters of 20, 70, 400 and 1000 nm were applied from suspensions of 3, 6, 12 and 25 mg/ml. The nanoparticle co-matrix had the effect of both increasing the analyte charge state as well as altering the relative intensity of the observed peak intensities. With the 20 and 70 nm particles, approximately one-third of the peaks decreased in intensity whereas one-fifth of the peaks increased in intensity. In general, the increase in intensity was observed in the m/z region below 4000 m/z. Continuing work is aimed at correlating the selectivity of the matrix with properties of the identified proteins and MSI using the nanoparticle co-matrix.<br/>

Nanoparticle co-matrix for multiply charged ions in MALDI imaging

255th National Meeting (2018)

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