LAUREATES: AWARDS AND HONORS (SCS)
161
CHIMIA 2003, 57, No. 4
Chimia 57 (2003) 161–167
© Schweizerische Chemische Gesellschaft
ISSN 0009–4293
Exploiting Long-Lived
Molecular Fluorescence
Werner M. Nau*, Fang Huang, Xiaojuan Wang, Huseyin Bakirci, Gabriela Gramlich,
and Cesar Marquez
*Werner Prize Winner 2002
Abstract: Fluorophores based on the azo chromophore 2,3-diazabicyclo[2.2.2]oct-2-ene, referred to as
fluorazophores, display an exceedingly long fluorescence lifetime. Besides the use in time-resolved screening
assays, where the long-lived fluorescence can be time-gated, thereby improving the signal to background
ratio, a distinct application of fluorazophores lies in the area of biopolymer dynamics. For this purpose, one
chain end is labeled with a fluorazophore and the other one with an efficient fluorescence quencher. The
fluorescence lifetime of the probe/quencher-labeled peptide then reflects the kinetics of intramolecular end-
to-end collision. Applications to polypeptides are described and control experiments which establish the
nature of the quenching mechanism as a diffusive process requiring intimate probe/quencher contact are
described.
Keywords: Azoalkanes · Fluorescence · Kinetics · Photochemistry · Peptides
Werner Nau graduated with a M.Sc. in Chem- tional fellowship, and a SNF Profil fellowship.
istry 1992 from St. Francis Xavier Universi- His work has led to the award of several
ty, Canada. His thesis was supervised by prizes, including the 1999 International Gram-
D. Klapstein and dealt with molecular spec- maticakis-Neumann prize for photochemistry,
troscopy (UV, IR, photoelectron) of acyl awarded by the Swiss Group for Photochem-
iso(thio)cyanates. He got his Ph.D. together istry and Photobiology, and the 2000 ADUC-
with W. Adam in 1994 from the University of Prize, awarded for his habilitation thesis.
Würzburg on the EPR and transient absorption
spectroscopy of 1,3-cyclopentanediyl diradi-
cals. Thereafter, Werner Nau spent his post-
doctoral studies with J.C. Scaiano at the Uni-
Fluorescent probes and sensors are
well-established tools in analytical and bio-
logical chemistry, spanning such diverse
applications as calcium ion detection, cell
staining, and polarity sensing [1]. An inter-
esting sub-class of fluorescent probes com-
prises chromophores with a particularly
long fluorescence lifetime, e.g. more than
50 ns [2]. Perhaps the simplest yet very im-
portant application based on long-lived
fluorescence (or generally luminescence)
versity of Ottawa, where he worked on the
mechanistic photochemistry of n,π*-excited
states. In 1996, he joined J. Wirz at the Uni-
versity of Basel, where he has started up with
an independent research group and became
a SNF assistant professor in 2000. In the
same year he finished his habilitation. Since
the fall semester 2002 he has been appointed
as a professor of chemistry at the newly
founded International University Bremen.
His research interests lie in the general
area of physical organic chemistry and fo-
cus on photochemistry, radical chemistry,
supramolecular chemistry, and biomolecular
chemistry, including both synthetic-prepara- relies on the reliable differentiation of long
tive, mechanistic, kinetic, and spectroscopic
aspects. He has recently introduced a novel
lived luminescence components. This is of
class of fluorescent probes, referred to as
fluorescence lifetimes from any shorter-
*Correspondence: Prof. Dr. W.M. Nau
School of Engineering and Science
International University Bremen
Campus Ring 1
interest, in particular, for screening assays
where fluorescent probes are employed to
signal molecular events such as the inhibi-
tion of an enzyme by a library of potential
drugs. Short-lived emission is ubiquitous
and may stem from other additives, sample
impurities, biological components, scat-
tered light, the solvent, or sample container
materials of cuvettes and microplates.
fluorazophores, which are based on the azo
chromophore of 2,3-diazabicyclo[2.2.2]oct-
2-ene. Fluorazophores are applied as sensors
for antioxidants, versatile guest molecules in
supramolecular chemistry, kinetic probes for
biopolymer folding, and fluorophores for time-
resolved screening assays.
Werner Nau has held numerous fellow-
ships, among others a Kekulé and Liebig
fellowship of the Fonds of the Chemical In-
dustry, a NATO fellowship, a NSERC Interna-
D–28759 Bremen
Tel.: +49 421 200 3233
Fax: +49 421 200 3229
E.Mail: w.nau@iu-bremen.de
and
Department of Chemistry
University of Basel
Klingelbergstrasse 80
CH–4056 Basel