LC/MS/MS MRM Library for Phospholipid Profiling
For LabSolutions Version 5
Phospholipid profiling can be broken down into two major steps: identifying and characterizing the hydrophilic “head”, followed by characterizing the hydrophobic “tail”. This MRM library targets phospholipids ranging from C14 to C22 with varying degrees of unsaturation for a total of 867 transitions. This library enables performing phospholipid profiling by first characterizing the phospholipid “head, followed by determining the fatty acid composition of the hydrophobic “tail”.
The phospholipids registered in the MRM library have fatty acid compositions with the carbon number and double bond combinations shown in the table below. The phospholipid targets of the library are phosphatidylcholines (PC) with a lyso-group, phosphatidylethanolamines (PE), phosphatidylglycerol (PG), phosphatidylinositol (PI), phosphatidylserines (PS), and sphingomyelins (SM).
MRM Transition Composition
Focusing on the characteristic phospholipid head group, the library includes a method for phospholipid classification and a method for fatty acid composition determination (for fatty acid compositions of the given combinations) that make use of these MRM transitions. The figure below shows each MRM transition required to identify PC (18:1/16:0). The phospholipid can be inferred by combining the analytical results obtained from these MRM transitions.
The phospholipid classification method is capable of comprehensive analysis of the main phospholipids in biological samples. It determines the phospholipid class based on the main characteristic head groups of phospholipids. Its analysis targets are phospholipids that include C14 to C22 fatty acids.
Step 2 Peak Identification
The phospholipid peak detected by the phospholipid classification method is identified. The structural information on the detected phospholipid at this point is the phospholipid class (PC, PE, PG, PI, PS, SM), and the total carbon number and number of double bonds in its constituent fatty acids. In the next step, the fatty acid composition determination method is created.
Step 3 MRM Event-Link Editor Editing the Fatty Acid Composition Determination Method
Software allows a fatty acid composition determination method to be edited from 867 MRM transitions for the phospholipid peak detected during first analysis.
Step 4 Simultaneous Analysis by Fatty Acid Composition Determination Method
Edited in MRM Event-Link Editor, the fatty acid composition determination method is used to perform a second analysis on the same sample. Phospholipid profiling can be performed based on the results of the first and second analysis.
Step 5 Data Analysis
Based on the analysis results, it was determined that the sample contains PC (16:0/20:1) and PC (18:0/18:1), as shown in the figures below.