Separation of fluorescent phosphatidyl inositol phosphates by CE.

Phosphatidyl inositol 4,5-bisphosphate (PIP2) and phosphatidyl inositol 3,4,5-trisphosphate (PIP3) labeled with 4,4-difluoro-5,7-dimethyl-4-bora-3a,4a-diaza-s-indacene-3-propionic acid (BODIPY FL) on the acyl chain or a phosphatidyl ethanolamine head group were separated by CE with LIF detection. Several methods and capillary-coating procedures were tested for the separation of these phosphatidyl inositol phosphates (PIPs) at 20 degrees C. Separation of the PIPs in less than 20 min with excellent resolution was achieved using a buffer containing sodium deoxycholate (SDC), 1-propanol, MgCl2 and the polymer coating reagent, EOTrol LR. The efficiency of the optimized method was as high as 1.3x10(5) plates. The dependence of the separation on the concentration of 1-propanol, SDC, and MgCl2 was determined. The separation of PIP2 and PIP3 was primarily due to differential binding of the lipids to Mg2+ rather than to different solubilities in the micellar phase. The role of the SDC was to prevent adsorption of the hydrophobic lipids to the capillary wall and thus enhance the efficiency. The fluorescent PIPs are of value for both in vitro and in vivo assays of phospholipid metabolism. In particular, the use of these lipids with the optimized capillary-based separation will be of utility for drug screening as well as cell-based assays.