Critical effects of polar fluorescent probes on the interaction of DHA with POPC supported lipid bilayers

The understanding of lipid bilayer structure and function has been advanced by the application of molecular fluorophores. However, the effects of these probe molecules on the physicochemical properties of membranes being studied are poorly understood. A quartz crystal microbalance with dissipation monitoring instrument was used in this work to investigate the impact of two commonly used fluorescent probes, 1-palmitoy1-2-(12- [(7-nitro-2-1,3-benzoxadiazol-4-yDamino]dodecanoy1}-sn-glycero-3-phosphocholine (NBD-PC) and 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine-n-(lissamine rhodamine-B-sulfonyl) (Lis-Rhod PE), on the formation and physicochemical properties of a 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine supported lipid bilayer (POPC-SLB). The interaction of the POPC-SLB and fluorophore-modified POPC-SLB with docosahexaenoic acid, DHA, was evaluated. The incorporation of DHA into the POPC-SLB was observed to significantly decrease in the presence of the Lis-Rhod PE probe compared with the POPC-SLB. In addition, it was observed that the small concentration of DHA incorporated into the POPC:NBD-PC SLB can produce rearrangement processes followed by the lost not only of DHA but also of POPC or NBD-PC molecules or both during the washing step. This work has significant implications for the interpretation of data employing fluorescent reporter molecules within SLBs.