A novel picosecond laser approach is used to investigate the intrinsic fluorescence of several oligonucleotides. All biomolecules are excited at 283 nm with laser pulses of typically 80 ps duration and an energy of 250 µJ; concentrations were on the order of 10 -5 M. Detection of the resulting fluorescence behind a spectrometer with a streak camera permits the simultaneous acquisition of spectral and lifetime information in two-dimensional images. In a systematic study, the fluorescence spectra and the associated temporal decays are analyzed with respect to monomer and potential excimer components. For this, the nucleotides AMP, CMP, GMP, and TMP are studied as well as homo-oligonucleotides of the type d(X) n with variable sequence length of n ) 2-15, enabling a comparison of the emission characteristics of these single-stranded compounds under physiologic conditions in solution at room temperature. Also, the influence of conformational changes on the fluorescence response is investigated using mixtures of complementary oligonucleotides d(X) 15 ×d(Y) 15 with the combinations X ) A, Y ) T and X ) G, Y ) C. These structures, which form double helices, differ in flexibility and stacking geometry from the single-stranded compounds. From experiments with self-complementary variants with alternating base sequences of the type d(XY) 8 with XY ) AT and GC, information on exciplex formation tendencies is obtained for these compounds, which also form double helices in solution. Preliminary results of time-dependent fluorescence anisotropy measurements with this direct picosecond laser approach are discussed.

Terpyridine ligands of the type Fc'-X-tpy (Fc'=ferrocenyl or octamethylferrocenyl, X=rigid spacer, tpy'=4'-substituted 2,2':6',2''-terpyridine) were prepared, crystallographically characterised and used for the synthesis of di- and trinuclear bis(terpyridine) complexes of RuII, FeII and ZnII. Donor-sensitiser dyads and triads based on RuII were thoroughly investigated by (spectro)electrochemistry, UV/Vis, transient absorption and luminescence spectroscopy, and an energy level scheme was derived on the basis of the data collected. Intramolecular quenching of the photoexcited RuII complexes by the redox-active Fc' groups can occur reductively and by energy transfer. Both the redox potential of the donor Fc' and the nature of the spacer X have a decisive influence on excited-state lifetimes and emission properties of the complexes. Some of the compounds show room-temperature luminescence, which is unprecedented for ferrocenyl-functionalised compounds of this kind.

Barley 2-cysteine peroxiredoxin (2-Cys Prx) was analyzed for peroxide reduction, quaternary structure, thylakoid attachment, and function as well as in vivo occurrence of the inactivated form, with emphasis on the role of specific amino acid residues. Data presented show the following. 1) 2-Cys Prx has a broad substrate specificity and reduces even complex lipid peroxides such as phosphatidylcholine dilineoyl hydroperoxide, although at low rates. 2) 2-Cys Prx partly becomes irreversibly oxidized by peroxide substrates during the catalytic cycle in a concentration-dependent manner, particularly by bulky hydroperoxides.

The fluorescence properties of tryptophan, polytryptophan and seven of its analogues (7-azatryptophan, 5-hydroxytryptophan, 5-methoxytryptophan, 5-fluorotryptophan, 5-methyltryptophan, 5-bromotryptophan, and 6-fluorotryptophan) are studied using two novel fluorescence spectroscopic techniques for a wide range of solvent polarities. Two-dimensional mapping of all emission and all fluorescence spectra using excitation-emission spectroscopy (EES) has been used to determine quantum yields, positions of emission maxima, full widths at half maximum (FWHMs) as well as Stokes' shifts. Additionally, fluorescence lifetimes obtained from time-resolved experiments using a picosecond laser system are presented and compared with the data acquired from the static setup. This systematic study of the fluorescence characteristics is a prerequisite to assess the potential of these analogues to act as structure-conserving substitutes for tryptophan in protein fluorescence experiments. The potential of these analogues, to act as probes for the local environment, and allow estimation of the polarity in the vicinity of the fluorophore and its exposure to the solvent, is discussed.

Kinases can be tagged with an engineered chemical probe that comprises a reversibly binding protein ligand, a photoreactive group (4‐benzoylphenylalanine), and a fluorescent reporter group (carboxyfluorescein). This principle, which does not require irreversible inhibitors, allows affinity‐based detection of protein families in functional proteomics.