Biotin-Phosphatidylserine is a biotinylated conjugate of phosphatidylserine (PS), a negatively charged phospholipid located in the inner leaflet of the cell membrane. During apoptosis PS is no longer restricted to the inner leaflet of the plasma membrane and migrates to the outer leaflet. Recognition of extra-leaflet PS by Anexin V is the basis of popular apoptosis assays. Similarly, during platelet activation, PS is translocated to the outer side where it facilitates assembly of the prothrombinase complex.
