Matrix-assisted laser desorption/ionization mass spectrometry imaging sample preparation using wet-interface matrix deposition for lipid analysis.

RATIONALE: Sample preparation is one of the most crucial steps for matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI). Scientists beginning their study with this technique may be overwhelmed by the variety of matrices, solvents, and concentrations; the methods of their applications; and the lack of widely available knowledge of the effect of these parameters on the results. Here we present in depth the aspects of matrix deposition, which will be helpful for the scientific community. METHODS: In this study, we tested several MALDI matrices, such as 2,5-dihydroxybenzoic acid (DHB), norharmane, N-(1-naphthyl)ethylenediamine dihydrochloride (NEDC), and 9-aminoacridine (9AA), using the SunCollect system: wet-interface matrix deposition in the context of lipid analysis. We optimized the number of matrix layers and nozzle settings in terms of spectral intensity and the overall quality of the obtained ion maps. RESULTS: Our research presents the effect of the number of matrix layers and nozzle settings on the results and allows for choosing the optimal parameters for the analyses. In positive ionization mode, DHB matrix could be chosen first. In the negative ionization mode, 1,5-diaminonaphthalene matrix produces a higher peak intensity in a lower mass range and seems to provide more information than 9AA. We recommend NEDC for particular processes such as glucose analysis. Compared to the remaining matrices, norharmane shows significant changes in the obtained ion maps. CONCLUSIONS: Such a large amount of data allow us to observe an interesting conclusion: the obtained ion image for a particular ion could differ dramatically with a change in the matrix, the solvent composition, or even the number of matrix layers. This must be considered when interpreting the result, impelling us to compare the results obtained with different matrices with caution.

The influence of matrix concentration and solvent composition on the results of MALDI MSI, with the aid of wet-interface matrix deposition.

Imaging mass spectrometry is a powerful technique for the molecular analysis of tissue sections. As in many analytical methods, sample preparation is one of the main and most important steps to obtain results of good quality. Usually, the matrix concentration and solvent composition in different studies are taken for granted without any further consideration. In our studies, we aimed to find how matrix concentration and a type of solvent influence the signal. Moreover, we also aimed to find the relationship between these parameters, how they influence the spectra, and how they influence obtained ion maps. In our experiments, we used SunCollect®, which is a commercially available wet-interface system for matrix deposition. We decided to choose two matrix concentrations (2,5-dihydroxybenzoic acid [DHB]: 15 and 25 mg/mL; 9-aminoacridine [9AA]: 7 and 5 mg/mL) and two different water solutions of solvents in two different percentages for the matrices (DHB: 50% and 70% of methanol [MeOH] and acetonitrile [ACN]; 9AA 70% and 50% of ethanol [EtOH] and MeOH). In the end, the influence of these parameters on obtained spectra and ion maps was assessed.

Gender differences in brain processes during inhibition of manual movements programs.

BACKGROUND: Motor response suppression can be regarded as an important aspect of the executive control, as a way of changing the behavioral pattern depending on the internal state or external factors. PURPOSE: The aim of our study was to examine whether there were differences in the ability of cortical inhibition of triggered motor program (in the context of the Stop-Signal task) between females and males. METHODS: We examined differences in the patterns of event-related EEG synchronization/desynchronization (ERS/ERD) in young volunteers under the conditions of complete inhibition of the triggered motor program of a manual movement. Thirty-six male and thirty-eight female (ages of 19 to 21) took part in the tests. The ERS and ERD indices were estimated within the EEG frequency range 8-35 Hz in frontal, central and parietal leads. RESULTS: In both gender groups, as a global pattern, the prevalence of connected phenomena with the EEG synchronization event in the range of α-activity of the EEG, apparently associated with inhibition of the running motor program was noted. CONCLUSION: Cortical electrical activity acquired certain specific features of the frequency-spatial organization, which could indicate the course of somewhat different brain processes of men and women.