Highly Responsive Fluorescent Assemblies Allow for Unique, Multiparametric Sensing of the Phospholipid Membrane Environment

Abstract

Despite decades-long extensive research, probes that provide a comprehensive description of the lipid membrane microenvironment are still lacking. We report here a 'smart' pyrene-terpyridine probe for multiparametric sensing of lipid membranes; wherein the complexity of the local microenvironment can be described by distinct features of the probe fluorescence. The self-assembly of the probe molecules in phospholipid bilayers is sensitive to membrane order and phase state. The self-assembled probes show a unique emission, influenced by dye-dye interactions and excited state charge transfer. Moreover, this emission is sensitive to interfacial hydration, with very specific changes in emission wavelengths and fluorescence lifetimes as lipid compositions and properties are varied. In parallel, changes in lipid order along with hydration affect the ground state interactions in dye-aggregates and thus can be measured through ratiometric changes in excitation and emission readouts. In addition, fluorescence anisotropy measurements provide another way to study the nature of dye-aggregates in lipid bilayers. Overall, here we demonstrate how multiple aspects of membrane microenvironment can be sensed through unique fluorescence signatures of this ҆smart҆ probe in lipid membranes, and establish a new paradigm in lipid membrane sensing.

A Tunable Palette of Molecular Rotors Allows Multicolor, Ratiometric Fluorescence Imaging and Direct Mapping of Mitochondrial Heterogeneity

“…Environment-sensitive dyes have been extremely valuable in studying the local chemical and physical environment of complex self-assemblies, biological membranes, protein dynamics, and living cells. − Molecular rotors constitute a particularly important class of environmentally sensitive dyes, long attracting intense interest as biological probes and for their excited-state dynamics. − Molecular rotors that are sensitive to various environmental parameters such as pH, polarity, and viscosity have been described. − Molecular rotors display a rich spectrum of excited-state dynamics that make them attractive for probing complex microenvironments inside living cells and their organelles. − Interestingly, despite decades of research, molecular rotors have largely been used as individual probes for sensing specific environmental parameters. While this can be valuable, single-dye probing has several limitations.…”

Hydrogen Bonding-Induced Unique Charge-Transfer Emission from Multichromophoric Polypyridyl Ligands: Ratiometric Probing of Methanol Impurity in Commercial Biofuels

“…Thus, we can assume better electronic communication between the aryl moiety and terpyridine unit in case of 1 than that of 2 . Furthermore, we also believe that the excited-state hydrogen bonding interaction in alcoholic solvents, especially in methanol, could planarize the molecules and enhance the CT interaction. − …”

Artificial Phospholipids and Their Vesicles

“…These films can be laterally compressed by a barrier, and the measured change in surface pressure certainly is one of the oldest ways to study ensembles of phospholipids . In the late 1980s and 1990s, powerful new techniques became available that enabled the probe-free (recently, a new push–pull pressure-sensitive fluorophore was introduced that does not change the organization of phospholipids, along with a multiparametric sensing fluorescent probe) study of the deeper structure of monolayers using synchrotron X-ray diffraction, , X-ray reflectivity, FTIR reflection absorption spectroscopy, , specular reflections of neutrons, and Brewster angle microscopy. , In particular, the X-ray scattering of phospholipid monolayers is now well understood, and beamlines such as the P08 of PETRA III of the Deutsches Synchrotron (DESY) allow routine measurements of lipid monolayers. In combination with the latest MatLab scripts, it is possible to analyze the results immediately after a measurement, which allows us to retake measurements make with faulty monolayer films …”