Researchers use new mass spectrometric technique to analyse metabolites
German and Czech researchers have developed a new technique to detect metabolites (substances involved in metabolism) in a quick yet comprehensive manner. Their findings have been published in the journal Proceedings of the National Academy of Sciences (PNAS). The researchers from the Max Planck Institute for Chemical Ecology in Germany and the Prague-based Academy of Sciences of the Czech Republic said the new method, called MAILD (matrix-assisted ionisation/laser desorption), is based on classical matrix-assisted laser desorption/ionisation-time of flight mass spectrometry (MALDI-TOF/MS). Researchers are able to measure many metabolites in biological samples, effectively allowing access for targeted and high-throughput metabolomics (the study of global metabolite profiles in a system (cell, tissue or organism) under a given set of conditions). Metabolites include amino acids, fatty acids and sugars, as well as other organic substances from animal or plant tissue samples. Biologists in particular have been using mass spectrometry in various applications, such as large biomolecules analyses, over the past 20 years. According to the German-Czech team, MALDI - the co-crystallisation of biomolecules (e.g. proteins) with a chemical substance called a matrix subsequently irradiated with a laser - triggers the formation of protein ions that can be identified and analysed. 'The ability to charge huge biomolecules without breaking them apart has made MALDI mass spectrometry an indispensable tool for biomolecular analysis. Conventional, empirically selected matrices produce abundant matrix ion clusters in the low-mass region, hampering the application of MALDI-MS to metabolomics,' the authors wrote. 'An ionisation mode of MAILD, a rational protocol for matrix selection based on [the] Brønsted-Lowry acid-base theory and its application to metabolomics, biological screening/profiling/imaging, and clinical diagnostics [are] illustrated,' the research showed. 'Numerous metabolites, covering important metabolic pathways (Krebs' cycle, fatty acid and glucosinolate biosynthesis), were detected in extracts, biofluids, and/or in biological tissues.' The researchers noted a downside, however: when matrices are used in the MALDI technique, the laser beam forms ions from the substances of interest, but it also forms low-mass ions originating from the matrix. 'Because of these small interfering ions, we were not able to analyse small molecules that play crucial roles in the metabolism of organisms,' explained Dr Aleš Svatoš, leader of the mass spectrometry/proteomics research group at the Max Planck Institute. 'The ions that originated from conventional matrices were like a haystack in which we wanted to find a few and important needles.' In order to improve their search, the researchers started modifying the matrices with which the samples were applied so as to hinder the production of interfering matrix-related ions. Doing so would help them make the 'needles' more visible. 'The analysis of a very small plant leaf sample from Arabidopsis thaliana, in fact a circle area with a radius of just about 0.5 millimetres, revealed over 100 analyte peaks, among which 46 metabolites could be identified,' said researcher Rohit Shroff. 'Interestingly, among them were 8 of a total of 11 intermediates of the citric acid cycle, which is vital for most organisms,' he added. According to the researchers, the new MAILD technique allows measurements from various biological and medical substances. Besides plant and insect samples, the team also assessed a clinical sample: they found a wide range of blood-specific organic acids in one drop of human blood - smaller than a micro litre. If the researchers successfully identify and quantify the metabolites, MAILD could become a quick method for medical and biological diagnostics.
Countries
Czechia, Germany