Discrimination of freshwater fish species by Matrix-Assisted Laser Desorption/Ionization- Time Of Flight Mass Spectrometry (MALDI-TOF MS): a pilot study

In this study we discriminate three freshwater fish species (the shad Alosa agone Scopoli 1786, the whitefish Coregonus macrophthalmus Nüsslin1882 and the roach Rutilus rutilus Linnaeus 1758) by Matrix-Assisted Laser Desorption/Ionization- Time Of Flight Mass Spectrometry (MALDI-TOF MS) using both muscle and liver tissues. The technology enables to analyze tissues after a simple single-step extraction procedure without any further purification. The molecular profile of muscle tissues showed the most intense peaks at m/z range of 11,354.0 (±2.0 SD) Da, 3508.5 (±1.5 SD) Da and 8567.2 (±1.1 SD) Da for the shad, the whitefish and the roach respectively. The molecular profiles of liver tissues exhibit most of the highest peak intensities in the range between 2000 and 6000 m/z values. The roach shows the clearest pattern with high intensities detected at mass ranges between 3000 and 3550 Da with maxima at m/z 3035.2 (±0.2) Da and 3468.7 (±0.3) Da. The shad shows a shared high peak at m/z 3429.0 (±0.3) Da. The whitefish shows a group of major peaks in the m/z range of 3000-3700 Da with the highest being at 3635 (±0.3) Da. The overall signal pattern generated is highly specific for each species and, according to cluster analyses based on the total number of peaks, we could discriminate the three species.