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Abstract

Molecular environment-sensitive probes offer the opportunity to chart physical and structural alterations on the nanoscale. Many areas of science have benefited from the unique information afforded by probes located within inaccessible spaces, which could not be collected by conventional techniques. Response to pH, polarity, temperature, extraneous metal ions, poisons and biomolecules are common place. Luminescence has certainly been one of the most popular methods used for readout purposes, since it is highly sensitive and non-intrusive when employed for biological applications. Temporal profiling is also possible with luminescence, so that timescales (e.g., picoseconds to milliseconds) for molecular events is achievable. There are a wealth of fluorescence reporters to date, some of which are tailor-made for specific purposes such as reactive oxygen species (ROS) detection, lipid mobility monitoring, protein sequencing and DNA/RNA recognition. Certainly one of the most versatile classes of fluorescent reporters to date is based on the borondipyrromethene (Bodipy) group. Generally, the fully alkylated molecule (BD) is strongly fluorescent in fluid solution at room temperature. It is very noticeable that fluorescence is much lower for certain fully non-alkylated versions (ROT), especially in non-viscous solvents. There is an enhancement (ca. 4 fold) in fluorescence quantum yield as the solvent viscosity increases by around 10 cP. The solvent viscosity effect is traced to reduction in the non-radiative decay process and the retardation in rotation of the meso aryl group with the increase in solvent viscosity. As the aryl group rotates it distorts slightly the pyrromethene backbone, which in turn affects the rate for non-radiative decay. The one problem with the first prototype of so-called Bodipy molecular rotor was the low starting point fluorescence output. We were especially interested to see if the original signal could be enhanced, with no detrimental effect on the overall fluorescence viscosity response. This talk will discuss our current progress in producing rheological probes (ROFRET) using intramolecular energy transfer to try and enhance the output signal.

Biography

Andrew C Benniston completed his PhD from Warwick University in 1990 and postdoctoral studies at the Universite Louis Pasteur (Strasbourg) and the University of Texas at Austin. He is Professor of Photonic Energy Sciences at Newcastle University. He has published more than 130 papers in major journals and is currently the Editor-In Chief for the Journal of Analytical & Bioanalytical Techniques.