A Comparison of Methods To Enhance Protein Detection of Lipoproteins by Mass Spectrometry

We sought to develop a new method
to more efficiently analyze lipid-bound
proteins by mass spectrometry using a combination of a lipid removal
agent (LRA) that selectively targets lipid-bound proteins and a mass
spectrometry compatible detergent, anionic acid labile surfactant
(AALS), that is capable of eluting proteins off the LRA. This method
was compared to established methods that use the lipid removal agent
alone and straight proteomic analysis of human plasma after organic
solvent delipidation (OSD). Plasma from healthy individuals was separated
by gel filtration chromatography and prepared for mass spectrometry
analysis by each of the described methods. The addition of AALS to
LRA increased the overall number of proteins detected in both the
high and low density lipoprotein size range, the number of peptide
counts for each protein, and the overall sequence coverage. Organic
solvent delipidation detected the most proteins, though with some
decrease in overall protein detection and sequence coverage due to
the presence of nonlipid-bound proteins. The use of LRA allows for
selection and analysis of lipid-bound proteins. The addition of a
mass spectrometry compatible detergent improved detection of lipid-bound
proteins from human plasma using LRA.