Abstract: Lipid assay method, kit, and apparatus involving exposure of a protein, having a lipid recognition motif that interacts with a target lipid and a competing lipid, to a solution containing the competing lipid, and determining whether the target lipid is present in the solution. The target lipid has a stronger affinity to the lipid recognition motif than does the competing lipid. The lipid recognition motif is preferably a pleckstrin homology (PH) domain, with the target lipid being a phosphoinositide. The assay determines activity of a lipid kinase, the target lipid being a phosphorylation product of a reaction between the lipid kinase and a substrate lipid. The assay can be a cancer screening method for detection of cancer cells, where detection of certain levels of a PI(3,4,5)P3 target lipid is an indicator of a cancer cell.

Abstract: The methods and compositions disclosed herein concern the synthesis of a novel class of “two-headed” phospholipid-phosphoinositide hybrids possessing a carbon backbone, such as 2,3-diacylthreitol, erythritol or a synthetic module. The second phospholipid head group allows introduction of a biochemical or chemical moiety in a position orthogonal in space to those occupied by the phosphoinositide head group and the two acyl chains. The diacyl moieties allow for the incorporation of Pea-PIP2 into a lipid bilayer, while the Ptdlns(4,5)P2 moiety in the aqueous layer is specifically recognized by lipid binding proteins. In alternative embodiments of the invention, reporters, for example biotin, fluorophores and/or spin labels, are attached to the free amino group of the head groups of such molecules to specifically target the reporters to the lipid-water interface.

Abstract: A lipid assay kit for detection of a lipid kinase or phosphatase and method of use thereof. The assay is preferably a competitive assay wherein the product lipid has a stronger affinity to the lipid detector protein than the substrate lipid. The lipid recognition motif is preferably a pleckstrin homology (PH) domain.