Fig. 7.

Iodine-containing SM observed in brain SM. Normal SM[d18:1,24:1(n-9)] (A) and iodine-containing SM (C). The carbon-carbon double bond region is expanded in (B). White arrows indicate backbone fragments from the normal SM. Black arrows indicate acyl group fragments. The 2H difference started at the n-9 position indicates the double bond location in the normal SM (D). In the case of the modified SM, fragment series of CH, O, and CH₃ were appeared. This indicates the modified SM has the structure shown in E.