Abstract
Neuromelanin (NM) isolated from the substantia nigra of the human brain is found to contain a series of dolichoic acids (dol-CA) containing 14-20 isoprene units. This is the first observation of dol-CA in a natural system. Using internally spiked nor-dolichol and nor-dolichoic acid standards, the concentrations of dolichol (dol) and dol-CA present in NM were determined. Remarkably, dol was only four times as abundant as dol-CA in NM. The distribution of dol-CA chains lengths in NM also differed from that of dol, suggesting that the enzyme(s) responsible for the conversion of dol to dol-CA prefer a dolichol substrate containing 19 isoprene units.
Highlights
Neuromelanin (NM) isolated from the substantia nigra of the human brain is found to contain a series of dolichoic acids containing 14–20 isoprene units
A nor-dolichol internal standard synthesized by Avanti Polar Lipids (Alabaster, AL) with n 5 13–21 was added to give a final concentration of 100 ng/ml, and 5 ml of the final mixture was injected onto a reversed-phase column for liquid chromatographymass spectrometry (LC/MS) analysis as described below
LC/MS of the lipid extract of NM isolated from the human substantia nigra (SN)
Summary
Neuromelanin (NM) isolated from the substantia nigra of the human brain is found to contain a series of dolichoic acids (dol-CA) containing 14–20 isoprene units. A nor-dolichol internal standard synthesized by Avanti Polar Lipids (Alabaster, AL) with n 5 13–21 (see supplementary Scheme I) was added to give a final concentration of 100 ng/ml, and 5 ml of the final mixture was injected onto a reversed-phase column for liquid chromatographymass spectrometry (LC/MS) analysis as described below. The series of peaks near m/z 1236, 1304, 1372, and 1440 are interpreted as the acetate adducts [M1Ac]2 of dol species with chain lengths of n 5 17, 18, 19, and 20, respectively (n denotes the number of isoprene units).
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