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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)
Femtosecond spectroscopy in combination with site-directed mutagenesis was used to study the influence of histidine L153 in primary electron transfer in the reaction center of Rhodopseudomonas viridis. Histidine was replaced by cysteine, glutamate, or leucine. The exchange to cysteine did not lead to significant changes in the primary reaction dynamics. In(More)
Femtosecond time-resolved spectroscopy on model peptides with built-in light switches combined with computer simulation of light-triggered motions offers an attractive integrated approach toward the understanding of peptide conformational dynamics. It was applied to monitor the light-induced relaxation dynamics occurring on subnanosecond time scales in a(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)
Femtosecond spectroscopy was used in combination with site-directed mutagenesis to study the influence of tyrosine M210 (YM210) on the primary electron transfer in the reaction center of Rhodobacter sphaeroides. The exchange of YM210 to phenylalanine caused the time constant of primary electron transfer to increase from 3.5 +/- 0.4 ps to 16 +/- 6 ps while(More)
M subunit Trp252 is the only amino acid residue which is located between the bacteriopheophytin HA and the quinone QA in the photosynthetic reaction centre of Rhodobacter sphaeroides. Oligodeoxynucleotide-directed mutagenesis was employed to elucidate the influence of this aromatic amino acid on the electron transfer between these two chromophores. For(More)
Detailed studies of the subpicosecond kinetics in the primary electron transfer of reaction centers of Rhodopseudomonas viridis The primary, light-induced charge separation in reaction centers of Rhodopseudomonas widis is investigated with femtosecond time resolution. The absorption changes after direct excitation of the primary donor P at 955 nm are(More)
Two-step excitation of retinal in bacteriorhodopsin by visible light is followed by an energy transfer to amino acids that is seen as fluorescent emission around 350 nm. The fluorescence spectrum obtained after two-step excitation (2 × 527 nm) differs from the fluorescence spectrum obtained after one-step ultraviolet excitation (263.5 nm) by a strongly(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)