Lipids are highly diverse group of biomolecules that play a pivotal role in biological processes. Lipid compositions of bio-fluids are complex, reflecting a wide range of concentration of different lipid classes with structural diversity within lipid species. Varying degrees of chemical complexity makes their identification and quantification challenging. Newer methods are thus, highly desired for comprehensive analysis of lipid species including identification of structural isomers. Herein, we propose a targeted-MRM method for large scale high-throughput lipidomics analysis using a combination of variable retention time window (variable-RTW) and relative dwell time weightage (relative-DTW) for different lipid species. With this method, we were able to detect more than 1000 lipid species (encompassing 18 lipid classes), including different structural isomers of triglyceride, diglyceride, and phospholipids, in a single-run of 24 minutes. The limit of detection varied between 0.245 pmol/L and 1 nmol/L for different lipid classes with 245 fmol/L being lowest for phosphatidylethanolamine while it was highest for diacylglycerol (1 nmol/L). Similarly, the limit of quantitation varied from 291 fmol/L to 2 nmol/L. The recovery of the method is in the acceptable range and the 849 of lipid species were found to have a coefficient of variance (CV) <30%. Using this method we demonstrate that lipids with ω-3 and ω-6 fatty acid chains are altered in individuals with vitamin B12 deficiency.
AVATAR: A Variable-Retention-Time (VRT) Aware Refresh for DRAM Systems
