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The primary electron transfer in reaction centers of Rhodobacter sphaeroides is studied by subpicosecond absorption spectroscopy with polarized light in the spectral range of 920-1040 nm. Here the bacteriochlorophyll anion radical has an absorption band while the other pigments of the reaction center have vanishing ground-state absorption. The transient(More)
In neurodegenerative diseases such as Alzheimer's disease (AD), Parkinson's disease (PD) and prion diseases, deposits of aggregated disease-specific proteins are found. Oligomeric aggregates are presumed to be the key neurotoxic agent. Here we describe the novel oligomer modulator anle138b [3-(1,3-benzodioxol-5-yl)-5-(3-bromophenyl)-1H-pyrazole], an(More)
The applicability and limits of time-resolved transillumination to determine the internal details of biological tissues are investigated by phantom experiments. By means of line scans across a sharp edge, the spatial resolution (Δx) and its dependence on the time-gate width (Δt) can be determined. Additionally, measurements of completely absorbing bead(More)
Femtosecond time-resolved infrared spectroscopy was used to study the formation of cyclobutane dimers in the all-thymine oligodeoxynucleotide (dT)18 by ultraviolet light at 272 nanometers. The appearance of marker bands in the time-resolved spectra indicates that the dimers are fully formed approximately 1 picosecond after ultraviolet excitation. The(More)
Photosystem II of oxygen-evolving organisms exhibits a bicarbonate-reversible formate effect on electron transfer between the primary and secondary acceptor quinones, QA and QB. This effect is absent in the otherwise similar electron acceptor complex of purple bacteria, e.g., Rhodobacter sphaeroides. This distinction has led to the suggestion that the iron(More)
The photodynamics of bacteriorhodopsin were studied by transient absorption and gain measurements after excitation with femtosecond pulses at 620 nm. With probing pulses at longer wavelengths (A> 770 nm) the previously reported formation of the J intermediate (with a time constant of 500f 100 fs) was confirmed. With probing pulses around 700 nm, a faster(More)
The primary processes of the photochemical cycle of light-adapted bacteriorhodopsin (BR) were studied by various experimental techniques with a time resolution of 5 x 10(-13) s. The following results were obtained. (a) After optical excitation the first excited singlet state S(1) of bacteriorhodopsin is observed via its fluorescence and absorption(More)
Stable subpicosecond infrared pulses in the spectral region of 4.5-11.5 microm are generated by difference-frequency mixing in AgGaS(2). The system uses femtosecond pulses from a Ti:sapphire regenerative amplifier and from a tunable traveling-wave dye laser. The infrared pulses have a duration of 400 fs, an energy of more than 10 nJ, and a repetition rate(More)
The initial electron transfer steps in the photosynthetic reaction center of the purple bacterium Rhodobacter sphaeroides have been investigated by femtosecond time-resolved spectroscopy. The experimental data taken at various wavelengths demonstrate the existence of at least four intermediate states within the first nanosecond. The difference spectra of(More)