We will present a new method to reduce the photobleaching of fluorescent proteins and the associated phototoxicity. Our method exploits a photophysical process known as reverse intersystem crossing, which we induce by near-infrared co-illumination during fluorophore excitation. This dual illumination method typically reduces photobleaching effects 4-fold, can be easily implemented on commercial microscopes and is effective in eukaryotic and prokaryotic cells with a wide range of fluorescent proteins.
KEYWORDS: Chemical analysis, Biological research, Process control, Temporal resolution, Biology, Nanoplasmonics, Sensors, Nanoparticles, Nanophotonics, Current controlled current source
The external control of biologically-active substrates with high spatial and temporal resolutions has already strongly impacted many fields of Biology. This lecture will illustrate how light can be used to control and analyze biological processes.
A multichromophoric nanoassembly was designed by gathering seven push-pull chromophores on a β-cyclodextrin assembling unit via covalent linkers. Such supermolecule provides a valuable model for the investigation of confinement effects on the linear and nonlinear optical properties of push-pull chromophores in the condensed phase. Push-pull chromophores display a significant ground-state dipole, thus promoting dipolar interactions that are expected to influence both the conformation and the optical properties of the multichromophoric assembly. In this perspective, the photophysical and nonlinear optical properties of the mutichromophoric bundle were investigated and compared to those of the monomeric chromophore. The absorption, circular dichroism and fluorescence investigations provide evidence that the push-pull chromophores do not behave as isolated independent chromophores within the multichromophoric assembly. The nanoscale supermolecule is hypsochromically and significantly hypochromically shifted with respect to its monomeric analogue. In addition, the close proximity promotes excitonic coupling, as well as excimer formation phenomena. The nanoscopic assembly also shows a very large dipolar moment (μ = 38 D), and a significant molecular first-order hyperpolarisability, which reveal a spontaneous sheaf-type self-arrangement of the dipolar chromophores within the supermolecule. Such chiral hyperpolar nanoassemblies are promising candidates as model systems for nanophotonics.
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