Laurdan (2-dimethylamino-6-lauroylnaphthalene) is a hydrophobic fluorescent probe widely used in lipid systems. This probe was shown to be highly sensitive to lipid phases, and this sensitivity related to the probe microenvironment polarity and viscosity. In the present study, Laurdan was incorporated in 1,2-dipalmitoyl-sn-glycero-3-[phospho-rac-(1-glycerol)] (DPPG), which has a phase transition around 41°C, and DLPC (1,2-dilauroyl-sn-glycero-3-phosphocholine), which is in the fluid phase at all temperatures studied. The temperature dependence of Laurdan fluorescent emission was analyzed via the decomposition into two gaussian bands, a short- and a long-wavelength band, corresponding to a non-relaxed and a water-relaxed excited state, respectively. As expected, Laurdan fluorescence is highly sensitive to DPPG gel–fluid transition. However, it is shown that Laurdan fluorescence, in DLPC, is also dependent on the temperature, though the bilayer phase does not change. This is in contrast to the rather similar fluorescent emission obtained for the analogous hydrophilic probe, Prodan (2-dimethylamino-6-propionylnaphthalene), when free in aqueous solution, over the same range of temperature. Therefore, Laurdan fluorescence seems to be highly dependent on the lipid bilayer packing, even for fluid membranes. This is supported by Laurdan fluorescence anisotropy and spin labels incorporated at different positions in the fluid lipid bilayer of DLPC. The latter were used both as structural probes for bilayer packing, and as Laurdan fluorescence quenchers. The results confirm the high sensitivity of Laurdan fluorescence emission to membrane packing, and indicate a rather shallow position for Laurdan in the membrane.
Similar content being viewed by others
References
G. Weber and F. J. Farris (1979). Synthesis and spectral properties of hydrofobic fluorescent probe: 6-Propionyl-2-(dimethylamino)naphthlene. Biochemistry 18, 3075–3078.
L. A. Bagatolli, E. Gratton, and G. D. Fidelio (1998). Water dynamics in glycosphingolipid aggregates studied by LAURDAN fluorescence, Biophys. J. 75, 331–341.
D. Zubiri, A. Domecq and D. L. Bernik (1999). Phase behavior of phosphatidylglycerol bilayers as a function of buffer composition: Fluorescence studies using Laurdan probe, Coll. Surf. B Biointer. 13, 13–28.
L. A. Bagatolli, T. Parasassi, G. D. Fidelio, and E. Gratton (1999). A model for the interaction of 6-Lauroyl-2-(N, N-dimethylamino)naphthalene with lipid environments: Implications for spectral properties, Photochem. Photobiol. 70(4), 4.
L. A. Bagatolli and E. Gratton (1999). Two-photon fluorescence microscopy observation of shape changes at the phase transition in phospholipid giant unilamellar vesicles, Biophys. J. 77, 2090–2101.
S. Vanounou, D. Pines, E. Pines, A. H. Parola and I. Fishov (2002). Coexistence of domains with distinct order and polarity in fluid bacterial membranes, Photochem. Photobiol. 76(1), 1–11.
T. Parasassi, G. Stasio, G. Ravagnan, R. M. Rusch, and E. Gratton (1991). Quantization of lipids phases in phospholipid vesicles by the generalized polarization of Laurdan fluorescence, Biophys. J. 60, 179–189.
T. Parasassi, E. K. Krasnowska, L. Bagatolli, and E. Gratton (1998). LAURDAN and PRODAN as polarity-sensitive fluorescent membrane probes, J. Fluorescence 8, 365–373.
R. M. Epand and R. Kraayenhof (1999). Fluorescent probes used to monitor membranes interfacial polarity, Chem. Phys. Lipids 101, 57–64.
R. B. Campbell, S. V. Balsubramanian, and R. M. Straubinger (2001). Phospholipd–cationic lipid interactions: Influences on membrane and vesicles properties, Biochim. Biophys. Acta 1512, 27–39.
T. Söderlund, J. M. I. Alakoskela, A. L. Pakkanen, and P. K. J. Kinnunen (2003). Comparison of the effects of surface tension and osmotic pressure on the interfacial hydration of a fluid phospholipid bilayer, Biophys. J. 85, 2333–2341.
J. R. Lakowicz (1999) Principles of Fluorescence Spectroscopy, 2nd ed. Kluwer Academic/Plenum Press, New York, pp. 185–289.
M. Viard, J. Gallay, M. Vincent, O. Meyer, B. Robert and M. Paternostre (1997). Laurdan solvatochromism: Solvent dielectric relaxation and intramolecular excited-state reaction, Biophys. J. 73, 2221–2234.
D. Marsh (1990) CRC Handbook of Lipids Bilayers. CRC Press, Boca Raton, Florida, pp. 219.
O. H. Griffith and P. C. Jost (1976) Lipids spin labels in biological membranes. In: L. J. Berliner (Ed.), Spin Labelling. Theory and Applications. Academic Press, New York, p. 453.
B. J. Gaffney (1976) Practical considerations for the calculations of order parameters for fatty acid or phospholipid spin labels in membranes. In: L. J. Berliner (Ed.), Spin Labelling. Theory and Applications. Academic Press, New York, p. 567.
W. L. Hubbell, and H. M. McConnell (1971). Molecular motion in spin-labeled phospholipids and membranes, J. Am. Chem. Soc. 93, 314–326.
M. Viard, J. Gallay, M. Vincent and M. Paternostre (2001). Origin of Laurdan sensitivity to the vesicle-to micelle transition of phospholipids–octylglucoside system: A time-resolved fluorescent study, Biophys. J. 80, 347–359.
D. Marsh (1981). Electron spin resonance: Spin labels. In: E. Grell (Ed.), Membrane Spectroscopy. Springer, Berlin, pp. 51–142.
C. R. Benatti, E. Feitosa, R. M. Fernandez and M. T. Lamy-Freund (2001). Structural and thermal characterization of dioctadecyldimethylammonium bromide dispersions by spin labels, Chem. Phys. Lipids 111, 93–104.
C. R. Benatti, J. M. Ruysschaert. and M. T. Lamy (2004). Structural characterization of diC14-amidine, a pH sensitive lipid used for transfection, Chem. Phys. Lipids 131, 197–204.
R. M. Fernadez and M. T. Lamy-Freund (2000). Correlation between the effects of a cationic peptide on the hydration and fluidity of anionic lipid bilayers: A comparative study with sodium ions and cholesterol, Biophys. Chem. 87, 87–102.
H. Schindler and J. Seelig (1973). EPR-spectra of spin labels in lipid bilayers, J. Chem. Phys. 59(4), 4.
O. H. Griffith, P. J. Dehlinger and S. P. Van (1974). Shape of hydrophobic barrier of phospholipid bilayers (evidence for water penetration in biological membranes), J. Membrane Biol. 15, 159–192.
ACKNOWLEDGMENTS
This work was supported by USP, FAPESP and CNPq. Fellowships for C.C.V.S. (FAPESP), C.R.B. (FAPESP) and M.T.L. (CNPq) are acknowledged.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
De Vequi-Suplicy, C.C., Benatti, C.R. & Lamy, M.T. Laurdan in Fluid Bilayers: Position and Structural Sensitivity. J Fluoresc 16, 431–439 (2006). https://doi.org/10.1007/s10895-005-0059-3
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s10895-005-0059-3