3-Hydroxychromone Probes Precisely Located and Oriented in Lipid Bilayers: A Toolkit for Biomembrane Research

Environment-sensitive dyes due to the sensitivity of their spectra to the physicochemical properties of their environment are unique tools for probing model and biological membranes. Here, we describe a particular class of environment-sensitive dyes based on 3-hydroxychromones. These dyes exhibit excited-state intramolecular proton transfer resulting in dual emission, highly sensitive to environment polarity and hydration. Appropriate molecular design of the new probes allows precise localization and orientation of their fluorophore in the lipid bilayers, which confer high specificity to particular membrane properties. In this respect, interface localization of the probes allows monitoring lipid order, while vertical orientation is required to achieve sensitivity to dipole and transmembrane potentials. Finally, biological applications of these probes for sensing lipid domains (rafts) and apoptosis are shown.