We have introduced a class of fluorescent probes known as fluorazophores based on 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO). These probes are are characterized by an exceedingly long fluorescence lifetime of up to 1 microsecond in water and feature a variety of unique quenching mechanisms. This allowed us to develop a technique to measure the antioxidant activity and mobility of various antioxidants (e.g. Vitamin E derivatives) in model membrane systems (Project I) as well as the flexibility of short peptides (Project II). By this technique we address fundamental problems in the life sciences, for example we investigate the kinetics of protein folding modeling and try to understand oxidative-stress related processes such as lipid peroxidation.
In an extension of the peptide flexibility project, we found that the natural amino acid tryptophan (Trp) is not only a collision-induced fluorescence quencher (CIFQ) for DBO, but that it can also act as a fluorescence resonance energy transfer (FRET) donor for DBO. This FRET pair has an extremely small Förster radius of only 10 Å and can thus serve as an accurate ruler for distance determinations in the 10-Å domain. The possibility to determine flexibility and distance distribution of short oligopeptides with the same Trp/DBO pair is unique and allowed us to probe a large variety of structural and dynamic properties of peptides such as conformational switching and coloumbic interactions.
Key References (Project I): a) Langmuir 2010, 26, 14723-14729; b) J. Am. Chem. Soc. 2007, 129, 10211-10219; c) J. Am. Chem. Soc. 2005, 127, 15575-15584; d) J. Am. Chem. Soc. 2004, 126, 5482-5492.
Key References (Project II): a) J. Phys. Chem. 2015, 119, 33-43; b) J. Am. Chem. Soc. 2007, 129, 9762-9772; c) ChemBioChem, 2007, 8, 567-573; d) J. Am. Chem. Soc. 2006, 128, 8118-8119; e) J. Am. Chem. Soc. 2004, 126, 16665-16675; f) Angew. Chem. Int. Ed. 2003, 42, 2269-2272; g) J. Am. Chem. Soc. 2002, 124, 556-564.