MALDI-TOF Mass Spectrometry of Oocyte Lipids

The spectra obtained with MALDI-TOF mass spectrometry were acquired in positive mode by a reflected Auto Flex Speed MALDI-TOF/TOF mass spectrometer (Bruker Daltonics, Bremen, Germany). Data were acquired in a mass range from 700–900 m/z with 1500 laser shots in different oocyte regions. The laser was applied until all signs had disappeared in the region of interest due to sample desorption. The laser intensity was standardized at 40% for the spectrum acquisition in all the samples. Spectra were centered and aligned using mMass 5.5.0 software [30 (link)]. The most intense ions upon the detection of peaks corresponding to isotopic distributions were considered as the starting point corresponding to the lipid ions. For the experiments, a total of 10–15 oocytes per group of fresh oocytes from the four different systems were used; no vitrified and warmed oocytes were evaluated.