Publications by authors named "Matthias M N Wolf"

Femtosecond polarization resolved UV/Vis and mid-infrared spectroscopy was used to thoroughly identify and characterize the relevant elementary chemical and physical processes in the photocycle of 3-hydroxyflavone (3-HF) in solution. In one set of experiments with the polar aprotic solvent acetonitrile-d(3), for the first time excited state intramolecular proton transfer (ESIPT), vibrational cooling/relaxation and rotational diffusion could be separated, and furthermore mid IR vibrational spectra of 3-HF excited states in solution phase were obtained. UV/Vis transient absorption data yield the time constant τ(Rot) = 22 ps for rotational diffusion and the time constant τ(VR) = 8.

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Isotope-labeled riboflavin in DMSO was employed in conjunction with femtosecond time-resolved infrared vibrational spectroscopy and quantum chemical calculations to analyze and assign the electronically excited state vibrational modes of the isoalloxazine unit as a prototype for the cofactors in flavin binding blue-light receptors. Using the riboflavin (13)C-analogues RF-2-(13)C and RF-4,10a-(13)C, the carbonyl vibrations, in particular, were studied. Various quantum chemical models were applied that take into account a polarizable environment or the impact of hydrogen bonds.

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To gain a better understanding of the light-induced reduction of protochlorophyllide (PChlide) to chlorophyllide as a key regulatory step in chlorophyll synthesis, we performed transient infrared absorption measurements on PChlide in d4-methanol. Excitation in the Q-band at 630 nm initiates dynamics characterized by three time constants: τ₁ = 3.6 ± 0.

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Essential for the biological function of the light-driven proton pump, bacteriorhodopsin (BR), and the light sensor, sensory rhodopsin II (SRII), is the coupling of the activated retinal chromophore to the hosting protein moiety. In order to explore the dynamics of this process we have performed ultrafast transient mid-infrared spectroscopy on isotopically labeled BR and SRII samples. These include SRII in D(2)O buffer, BR in H(2)(18)O medium, SRII with (15)N-labeled protein, and BR with (13)C(14)(13)C(15)-labeled retinal chromophore.

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Bacteriorhodopsin, reconstituted with a sterically "locked" retinal chromophore, BR5.12, has frequently been used to elucidate elementary photoinduced processes in the native pigment bacteriorhodopsin. In this work, the vibrational response of BR5.

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Femtosecond time-resolved infrared spectroscopy was used to study the vibrational response of riboflavin in DMSO to photoexcitation at 387 nm. Vibrational cooling in the excited electronic state is observed and characterized by a time constant of 4.0 +/- 0.

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The photoinduced low-spin (S = 0) to high-spin (S = 2) transition of the iron(ii) spin-crossover systems [Fe(btpa)](PF(6))(2) and [Fe(b(bdpa))](PF(6))(2) in solution have been studied for the first time by means of ultrafast transient infrared spectroscopy at room temperature. Negative and positive infrared difference bands between 1000 and 1065 cm(-1) that appear within the instrumental system response time of 350 fs after excitation at 387 nm display the formation of the vibrationally unrelaxed and hot high-spin (5)T(2) state. Vibrational relaxation is observed and characterized by the time constants 9.

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Phytochromes are light-sensing pigments found in plants and bacteria. For the first time, the P(fr) photoreaction of a phytochrome has been subject to ultrafast infrared vibrational spectroscopy. Three time constants of 0.

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