Fig. 2.

LC–ESI-MSⁿ analysis of 24S,25-epoxycholesterol in brain of wt mouse following treatment with cholesterol oxidase and derivatisation with GP-reagent. Reconstructed ion chromatograms (RICs) of (A) m/z 532.3898, (B) 550.4003 and 564.4160. MS³ fragmentation spectra of the peaks eluting at (D) 6.64 min and (E) 7.67 min in the RIC of m/z 532.3898, at (F) 3.33 min in the RIC of m/z 550.4003 and at (G) 6.00 min in the RIC of m/z 564.4160. Structures of the oxidised/derivatised molecules are shown as insets. Fragment ions are described in Karu et al. [20]. Syn and anti forms of the derivatives are formed resulting in duplicate peak for 24S,25-epoxycholesterol at 6.64 and 6.87 in (A), for 24,25-dihydroxycholesterol at 3.33 and 4.15 min in (B) and for 24-hydroxy-25-methoxycholesterol at 6.00 and 6.46 min in (C). Other peaks in (B) correspond to oxidised/derivatised unresolved 7α,24- and 7α,25-dihydroxycholesterols at 5.40 min, 7α,26-dihydroxycholesterol at 5.84 and 6.84 min, 7α,25-dihydroxycholesterol at 6.29 min and 7α,24-dihydroxycholesterol at 6.47 min.