The chemical synthesis of N-[1-(2-naphthol)]-phosphatidylethanolamine, a fluorescent phospholipid for excited-state proton transfer studies.
A procedure for the preparation of N-[1-(2-naphthol)]-phosphatidylethanolamine (NAPH-PE) has been developed. The synthesis is based on the Schiff base formation between the NH2 of the phospholipid and the aldehyde moiety of 2-hydroxy-1-naphthaldehyde. Then selective reduction of the imine is used to obtain the stable secondary amine, NAPH-PE. Formation of the intermediate Schiff base and the final product is confirmed by 13C- and 1H-NMR. Similar to free 2-naphthol, the excited-state pKa (pKa*) of its phospholipid derivative appears to be significantly lower than the ground-state pKa. At pH 7.4, the excitation spectrum of NAPH-PE shows no deprotonated species in the ground-state, while the emission spectrum presents a significant contribution of this species. Thus the fluorescent phospholipid exhibits the typical behavior of excited-state proton-transfer probes. NAPH-PE is found to incorporate in dimyristoyllecithin (DML) vesicles. The emission spectrum of the probe inserted in the liposomes is affected by acetate used as a proton acceptor. These properties should also be manifest in other lipid bilayers (e.g., plasma membranes of cells) and used for excited-state proton transfer studies.
Neyroz
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Istituto di Chimica Biologica, Facoltà di Medicina e Chirurgia, Università degli Studi di Parma, Italy.
Franzoni
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L
Spisni
A
A
Masotti
L
L
Brand
L
L
D005453:Fluorescence; D005456:Fluorescent Dyes / Q000138:chemical synthesis*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008055:Lipids / Q000032:analysis; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008566:Membranes / Q000737:chemistry; D009281:Naphthalenes / Q000032:analysis; D055095:Optics and Photonics; D010714:Phosphatidylethanolamines / Q000032:analysis / Q000138:chemical synthesis*; D011522:Protons; D013057:Spectrum Analysis / Q000379:methods
D005456:Fluorescent Dyes; D008055:Lipids; D009281:Naphthalenes; D010714:Phosphatidylethanolamines; D011522:Protons; C076787:N-(1-(2-naphthol))phosphatidylethanolamine; C062247:2-hydroxy-1-naphthaldehyde; C020888:1,2-dielaidoylphosphatidylethanolamine; C018525:1,2-dimyristoylphosphatidylethanolamine