31P NMR spectra of the organic extracts of detergent-treated boar spermatozoa. Sperm cells were incubated with the indicated detergents for 30 min at 4°C and phospholipids were extracted as described in the "Materials and Methods" section. Individual samples (organic extracts) were evaporated to dryness and subsequently re-dissolved in aqueous sodium cholate according to (31). Sodium cholate is the detergent of choice because it prevents formation of supramolecular phospholipid aggregates and forms very small micelles that are characterized by high mobility and provide, therefore, highly resolved 31P NMR spectra. The numerical values correspond to the amount of PL [nmol] detected in the individual samples and were calculated in comparison to a known amount of PA 14:0/14:0 (not shown) that was added in a final concentration of 10 μg per sample. Abbreviations used in peak assignments: SM, sphingomyelin; PC, phosphatidylcholine; PE, phosphatidylethanolamine. The applied detergents are explicitly given in the different traces.