Positive ion MALDI-TOF mass spectra of the organic extracts of detergent-treated boar spermatozoa. Sperm cells were incubated with detergents for 30 min at 4°C and lipids were extracted as described in Materials and Methods. The organic extracts were directly used for MALDI-TOF MS. Selected peaks are labelled according to their m/z ratios. The dotted vertical lines indicate the characteristic spermatozoa lipids at m/z = 369.3 (cholesterol) as well as 792.6 and 814.6 (GPCPlasm). The applied detergents are explicitly given in the different traces. For further details see Materials and Methods section.