Fluidity of lipid membranes is known to play an important role in the functioning of living organisms. The fluorescent probe Laurdan embedded in a lipid membrane is typically used to assess the fluidity state of lipid bilayers by utilizing the sensitivity of Laurdan emission to the properties of its lipid environment. In particular, Laurdan fluorescence is sensitive to gel vs liquid⁻crystalline phases of lipids, which is demonstrated in different emission of the dye in these two phases. Still, the exact mechanism of the environment effects on Laurdan emission is not understood. Herein, we utilize dipalmitoylphosphatidylcholine (DPPC) and dioleoylphosphatidylcholine (DOPC) lipid bilayers, which at room temperature represent gel and liquid⁻crystalline phases, respectively. We simulate absorption and emission spectra of Laurdan in both DOPC and DPPC bilayers with quantum chemical and classical molecular dynamics methods. We demonstrate that Laurdan is incorporated in heterogeneous fashion in both DOPC and DPPC bilayers, and that its fluorescence depends on the details of this embedding.

Faculty of Science Department of Physical and Macromolecular Chemistry Charles University Prague Hlavova 8 12840 Prague Czech Republic

Institute of Organic Chemistry and Biochemistry Academy of Sciences of the Czech Republic Flemingovonám 2 16610 Prague Czech Republic

J Heyrovský Institute of Physical Chemistry Czech Academy of Sciences Dolejškova 3 18223 Prague Czech Republic

See more in PubMed

Lakowicz J. Instrumentation for fluorescence spectroscopy.Principles of Fluorescence Spectroscopy. Springer; New York, NY, USA: 1999.

Bagatolli L., Gratton E. Two-photon fluorescence microscopy observation of shape changes at the phase transition in phospholipid giant unilamellar vesicles. Biophy. J. 1999;77:2090–2101. doi: 10.1016/S0006-3495(99)77050-5. PubMed DOI PMC

Simons K., Gerl M.J. Revitalizing membrane rafts: New tools and insights. Nat. Rev. Mol. Cell Biol. 2010;11:688–699. doi: 10.1038/nrm2977. PubMed DOI

Parasassi T., De Stasio G., Ravagnan G., Rusch R., Gratton E. Quantitation of lipid phases in phospholipid vesicles by the generalized polarization of laurdan fluorescence. Biophy. J. 1991;60:179–189. doi: 10.1016/S0006-3495(91)82041-0. PubMed DOI PMC

Barucha-Kraszewska J., Kraszewski S., Ramseyer C. Will c-laurdan dethrone laurdan in fluorescent solvent relaxation techniques for lipid membrane studies? Langmuir. 2013;29:1174–1182. doi: 10.1021/la304235r. PubMed DOI

Osella S., Murugan N.A., Jena N.K., Knippenberg S. Investigation into biological environments through (non) linear optics: A multiscale study of laurdan derivatives. J. Chem. Theory Comput. 2016;12:6169–6181. doi: 10.1021/acs.jctc.6b00906. PubMed DOI

Cwiklik L., Aquino A.J.A., Vazdar M., Jurkiewicz P., Pittner J., Hof M., Lischka H. Absorption and fluorescence of prodan in phospholipid bilayers: A combined quantum mechanics and classical molecular dynamics study. J. Phys. Chem. A. 2011;115:11428–11437. doi: 10.1021/jp205966b. PubMed DOI

Runge E., Gross E.K. Density-functional theory for time-dependent systems. Phys. Rev. Lett. 1984;52:997. doi: 10.1103/PhysRevLett.52.997. DOI

Becke A.D. Density-functional exchange-energy approximation with correct asymptotic behavior. Phys. Rev. A. 1988;38:3098. doi: 10.1103/PhysRevA.38.3098. PubMed DOI

Adamo C., Barone V. Toward reliable density functional methods without adjustable parameters: The pbe0 model. J. Chem. Phys. 1999;110:6158–6170. doi: 10.1063/1.478522. DOI

Kendall R.A., Dunning T.H., Jr., Harrison R.J. Electron affinities of the first-row atoms revisited. Systematic basis sets and wave functions. J. Chem. Phys. 1992;96:6796–6806. doi: 10.1063/1.462569. DOI

Ahlrichs R., Bär M., Häser M., Horn H., Kölmel C. Electronic structure calculations on workstation computers: The program system turbomole. Chem. Phys. Lett. 1989;162:165–169. doi: 10.1016/0009-2614(89)85118-8. DOI

Jambeck J.P., Lyubartsev A.P. Derivation and systematic validation of a refined all-atom force field for phosphatidylcholine lipids. J. Phys. Chem. B. 2012;116:3164–3179. doi: 10.1021/jp212503e. PubMed DOI PMC

Vega C., de Miguel E. Surface tension of the most popular models of water by using the test-area simulation method. J. Chem. Phys. 2007;126:154707. doi: 10.1063/1.2715577. PubMed DOI

Wang J., Wang W., Kollman P.A., Case D.A. Antechamber: An accessory software package for molecular mechanical calculations. J. Am. Chem. Soc. 2001;222:U403.

Wang J.M., Wolf R.M., Caldwell J.W., Kollman P.A., Case D.A. Development and testing of a general amber force field (vol 25, pg 1157, 2004) J. Comput. Chem. 2005;26:1157–1174. PubMed

Frisch M., Trucks G., Schlegel H.B., Scuseria G., Robb M., Cheeseman J., Scalmani G., Barone V., Mennucci B., Petersson G. Gaussian 09, Revision A. 02. Gaussian Inc.; Wallingford, CT, USA: 2009.

Barucha-Kraszewska J., Kraszewski S., Jurkiewicz P., Ramseyer C., Hof M. Numerical studies of the membrane fluorescent dyes dynamics in ground and excited states. Biochim. Biophys. Acta-Biomembr. 2010;1798:1724–1734. doi: 10.1016/j.bbamem.2010.05.020. PubMed DOI

Lamoureux G., Harder E., Vorobyov I.V., Roux B., MacKerell A.D. A polarizable model of water for molecular dynamics simulations of biomolecules. Chem. Phys. Lett. 2006;418:245–249. doi: 10.1016/j.cplett.2005.10.135. DOI

Pederzoli M., Sobek L., Brabec J., Kowalski K., Cwiklik L., Pittner J. Fluorescence of prodan in water: A computational qm/mm md study. Chem. Phys. Lett. 2014;597:57–62. doi: 10.1016/j.cplett.2014.02.031. DOI

Essmann U., Perera L., Berkowitz M.L., Darden T., Lee H., Pedersen L.G. A smooth particle mesh ewald method. J. Chem. Phys. 1995;103:8577–8593. doi: 10.1063/1.470117. DOI

Hess B., Kutzner C., van der Spoel D., Lindahl E. Gromacs 4: Algorithms for highly efficient, load-balanced, and scalable molecular simulation. J. Chem. Theory Comput. 2008;4:435–447. doi: 10.1021/ct700301q. PubMed DOI

Barbatti M., Ruckenbauer M., Plasser F., Pittner J., Granucci G., Persico M., Lischka H. Newton-x: A surface-hopping program for nonadiabatic molecular dynamics. Rev. Comput. Mol. Sci. 2014;4:26–33. doi: 10.1002/wcms.1158. DOI