Phospholipids: Functions and Analysis

Phospholipid molecules are a class of amphiphilic compounds with phosphate groups, containing both a hydrophobic tail consisting of fatty acid chains and a hydrophilic head consisting of substituted groups linked by phosphate. There are seven major groups of phospholipids in plasma: Phosphatidylcholine (PC), Lyso-phosphatidylcholine (Lyso-PC), Phosphatidylethanolamine (PE), Phosphatidylserine (PS), Phosphatidylinositol (PI), Phosphatidylglycerol (PG), and Sphingomyelin (SM).

Functions of phospholipids

Phospholipids not only maintain the normal morphology of cell membranes, but also participate in a large number of vital activities of living organisms.

Phospholipids play an important role in signaling, substance exchange, apoptosis and proliferation, e.g. glycerophospholipids are the precursors of lipid second messengers.

Phospholipid metabolites also play an important role in fever, inflammatory response and platelet aggregation, such as arachidonic acid, prostaglandins and platelet-activating factor.

Studies have shown that phospholipids are important bioactive substances and storage forms of information molecule precursors in the body. Its hydrolysis and oxidation products can regulate human metabolism by affecting the secretory or nervous system, improve memory, etc. It is also a chemical mediator in the formation of many diseases.

In addition, many diseases have been reported to be associated with abnormal phospholipid metabolism, such as diabetes, Alzheimer's disease, pancreatic cancer, etc. Therefore, in recent years, research targeting the structure, function and metabolism of phospholipids has become a hot topic in biology, medicine and pharmacology.

Each phospholipid is not a simple compound. The composition of phospholipids, depending on the polar head groups, the length of carbon chains, and the number of unsaturated bonds, is highly complex and diverse, so the analysis of phospholipids can be very difficult.

Phospholipid detection methods

Due to the development of soft ionization techniques (electrospray ionization (ESI) and matrix-assisted laser desorption ionization (MALDI)), mass spectrometry detectors are increasingly used in the analysis of phospholipids. The soft ionization technique, which produces almost no fragment ions, is particularly suitable for the identification of the molecular weight of complex compounds. In contrast, mass spectrometry, represented by high-resolution time-of-flight TOF, has powerful qualitative capabilities and is particularly suitable for the identification of complex mixtures of phospholipids.

Although the linear range of ESI in quantitation is not as wide as UV detector, mass spectrometry detection has the advantage of low detection limit and good specificity. Compared to other chromatographic common detectors, when performing quantitative chromatographic analysis, it is necessary to ensure the singularity of the chromatographic peak, and the chromatographic peak must not contain other interfering components. Mass spectrometry is less demanding in this regard, allowing for multiple reaction monitoring, parent ion, daughter ion scanning and neutral loss scanning, making it more suitable for the identification of low concentrations of phospholipids in complex matrices.

Creative Proteomics uses liquid chromatography-electrospray ionization mass spectrometry (LC-ESI/MS) as the core research tool for phospholipid studies, providing a wide range of services for disease diagnosis and new drug development.