CONICET | Buscador de Institutos y Recursos Humanos

Derivatives from 6-dimethylamine-2-naphthalenyl (DAN) are fluorescent probes with highsensitivity for the polarity and dynamic of their surroundings. This is due to the strategicposition of an electron donor and an electron acceptor group on opposite ends of thenaphthalene ring, resulting in a substantial increase in dipole moment upon excitation.LAURDAN is a member of the DAN family with a high affinity for lipid interfaces. Itsemission spectrum exhibits a significant red shift of 40 nm during the transition from thegel phase to the liquid-crystalline phase. This shift is linked to the extent of water dipolarrelaxation at the lipid interface, a direct manifestation of the membrane's physical state.In addition, the ground state of LAURDAN also carries information about its surroundings.Apart from its typical excitation band around 340 nm, there is a distinctive second bandaround 390 nm, influenced by the local electronic environment. This second excitationband is also sensitive to the phase state in lipid bilayers. In this study, we exploreLAURDAN's excitation-emission matrices (EEM) by using spectral phasor analysis and itsnovel extension to the excitation dimension, known as multi-dimensional spectral phasors(MdSP). Building upon this foundation, we were able to construct a theoretical Phase Map,providing insights into both lamellar and non-lamellar structures. For this, we developed acomputer algorithm that allowed us to construct EEM data based on a model forLAURDANs photophysics. The analysis of the constructed data reveals that all thepossibilities lie inside a universal triangle in the phasors plot, which we use to define alipid Phase Map. This approach is validated experimentally by using various wellestablished conditions, affirming the potential of MdSP to decode valuable informationfrom LAURDAN's EEM. Furthermore, the generality of our methodology could potentiallybe extended for other fluorescence probes.

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