Phosphatidylserine (PS) is a glycerophospholipid consisting of a phosphatidyl group attached to L-serine via a phosphodiester linkage. PS is a critical component of the cellular plasma membrane and accounts for 2-15% of plasma membrane lipid composition, depending on the cell/tissue type. The highest concentrations of PS are found in neuronal tissues, where it is critical for maintaining conduction velocity in myelinated neurons, as well as for higher order cognitive skills such as learning and memory. In normal, healthy cells, PS is held in the inner membrane surface (facing the cytosol) by the lipid transporter protein flippase. However, in apoptotic cells, PS molecules ‘shuffle’ between the inner and outer plasma membrane monolayers. When PS molecules flip to the extracellular (outer) surface of the cell membrane, they act as a signal for macrophages to engulf and digest the (apoptotic) cell. BioVision’s Phosphatidylserine Assay Kit allows for quantification of PS in lipid extracts of cell/tissue lysates. The assay is based on the enzymatic cleavage of PS to yield phosphatidic acid and L-serine, which is subsequently metabolised and reacts with a probe to form a stable fluorophore (Ex/Em = 538/587 nm). The assay is selective for PS (other phospholipids such as phosphatidylcholine, phosphatidylethanolamine or phosphatidic acid do not interfere). The kit is high-throughput ready and highly sensitive (can detect as little as 50 pmole/well of PS (5 µM in a 10 µl sample volume)).
Biochemical and cellular assays