Lipid analysis of human HDL and LDL by MALDI-TOF mass spectrometry and P-31-NMR

The analysis of HDL and LDL is important for the further understanding of a therosclerosis because changes of the protein and lipid moieties occur unde r pathological conditions. Because destruction of lipids leads to the forma tion of well-defined products such as lysophospholipids or chlorohydrins, m ethods that allow their fast and reliable determination would be useful. In this study, matrix-assisted laser desorption and ionization time-of-flight mass spectrometry (MALDI-TOF MS) was applied for the analysis of the lipid composition of human lipoproteins. These data were compared with high reso lution P-31-NMR spectroscopy. Differences between LDL and HDL in sphingomye lin and phosphatidylcholine content could be monitored by NMR and mass spec trometry, and differences with respect to the extraction efficiency were fo und by MALDI-TOF MS. Additionally, treatment of LDL with hypochlorite and p hospholipase A(2) resulted in marked changes (formation of chlorohydrines a nd lysolipids). Lysophosphatidylcholines were detectable by both methods, w hereas MALDI-TOF MS failed to detect chlorohydrines of phospholipids. We co nclude that MALDI-TOF MS provides rapidly a reliable lipid profile of lipop roteins. However, a previous lipid separation must be performed to detect l ipid oxidation products. NMR can be directly applied, but suffers from lowe r sensitivity, and provides only limited information on fatty acid composit ion.