Rhodopsin-cyclases for photocontrol of cGMP/cAMP and 2.3 Å structure of the adenylyl cyclase domain.

The cyclic nucleotides cAMP and cGMP are important second messengers that orchestrate fundamental cellular responses. Here, we present the characterization of the rhodopsin-guanylyl cyclase from Catenaria anguillulae (CaRhGC), which produces cGMP in response to green light with a light to dark activity ratio >1000. After light excitation the putative signaling state forms with τ = 31 ms and decays with τ = 570 ms.

Absorption and Emission Spectroscopic Investigation of Thermal Dynamics and Photo-Dynamics of the Rhodopsin Domain of the Rhodopsin-Guanylyl Cyclase from the Nematophagous Fungus Catenaria anguillulae.

The rhodopsin-guanylyl cyclase from the nematophagous fungus belongs to a recently discovered class of enzymerhodopsins and may find application as a tool in optogenetics. Here the rhodopsin domain CaRh of the rhodopsin-guanylyl cyclase from was studied by absorption and emission spectroscopic methods. The absorption cross-section spectrum and excitation wavelength dependent fluorescence quantum distributions of CaRh samples were determined (first absorption band in the green spectral region).

Reaction dynamics of the chimeric channelrhodopsin C1C2.

Channelrhodopsin (ChR) is a key protein of the optogenetic toolkit. C1C2, a functional chimeric protein of Chlamydomonas reinhardtii ChR1 and ChR2, is the only ChR whose crystal structure has been solved, and thus uniquely suitable for structure-based analysis. We report C1C2 photoreaction dynamics with ultrafast transient absorption and multi-pulse spectroscopy combined with target analysis and structure-based hybrid quantum mechanics/molecular mechanics calculations.

The rhodopsin-guanylyl cyclase of the aquatic fungus Blastocladiella emersonii enables fast optical control of cGMP signaling.

Blastocladiomycota fungi form motile zoospores that are guided by sensory photoreceptors to areas of optimal light conditions. We showed that the microbial rhodopsin of Blastocladiella emersonii is a rhodopsin-guanylyl cyclase (RhGC), a member of a previously uncharacterized rhodopsin class of light-activated enzymes that generate the second messenger cyclic guanosine monophosphate (cGMP). Upon application of a short light flash, recombinant RhGC converted within 8 ms into a signaling state with blue-shifted absorption from which the dark state recovered within 100 ms.

Light-Dark Adaptation of Channelrhodopsin Involves Photoconversion between the all-trans and 13-cis Retinal Isomers.

Channelrhodopsins (ChR) are light-gated ion channels of green algae that are widely used to probe the function of neuronal cells with light. Most ChRs show a substantial reduction in photocurrents during illumination, a process named "light adaptation". The main objective of this spectroscopic study was to elucidate the molecular processes associated with light-dark adaptation.

The chromophore structure of the long-lived intermediate of the C128T channelrhodopsin-2 variant.

The photocycle of the light-activated channel, channelrhodopsin-2 C128T, has been studied by resonance Raman (RR) spectroscopy focussing on the intermediates P380 and P353 that constitute a side pathway in the recovery of the parent state. The P353 species displays a UV-vis absorption spectrum with a fine-structure reminiscent of the reduced-retro form of bacteriorhodopsin, whereas the respective RR spectra differ substantially. Instead, the RR spectra of the P380/P353 intermediate couple are closely related to that of a free retinal in the all-trans configuration.

Neocortical excitation/inhibition balance in information processing and social dysfunction.

Severe behavioural deficits in psychiatric diseases such as autism and schizophrenia have been hypothesized to arise from elevations in the cellular balance of excitation and inhibition (E/I balance) within neural microcircuitry. This hypothesis could unify diverse streams of pathophysiological and genetic evidence, but has not been susceptible to direct testing. Here we design and use several novel optogenetic tools to causally investigate the cellular E/I balance hypothesis in freely moving mammals, and explore the associated circuit physiology.

The use of FTIR spectroscopy to assess quantitative changes in the biochemical composition of microalgae.

A mid-infrared spectroscopic method was developed for the simultaneous and quantitative determination of total protein, carbohydrate and lipid contents of microalgal cells. Based on a chemometric approach, measured FTIR (Fourier transform infrared) spectra from algal cells were reconstructed by a partial least square algorithm, using the spectra of the reference substances to determine their relative contribution to the overall cell spectrum. From this specific absorption, absolute macromolecular cell composition [pg cell(-1)] can be calculated using calibration curves, which have been validated by independent biochemical methods.

Evolution of the channelrhodopsin photocycle model.

Many processes in green algae are under control of rhodopsin-type photoreceptors, but only a few have been studied at least in some detail in the past. Up to now, functionally and biochemically only the channelrhodpsins ChR1 and ChR2 are characterized. Thus, this short review reports on channelrhodopsin properties with a strong focus on the knowledge about the photoreaction cycle(s).

The branched photocycle of the slow-cycling channelrhodopsin-2 mutant C128T.

Channelrhodopsins (ChRs) of green algae such as Chlamydomonas are used as neuroscience tools to specifically depolarize cells with light. A crude model of the ChR2 photocycle has been recently established, but details of the photoreactions are widely unknown. Here, we present the photoreactions of a slow-cycling ChR2 mutant (step function rhodopsin), with C128 replaced by threonine and 200-fold extended lifetime of the conducting-state P520.

Channelrhodopsins of Volvox carteri are photochromic proteins that are specifically expressed in somatic cells under control of light, temperature, and the sex inducer.

Channelrhodopsins are light-gated ion channels involved in the photoresponses of microalgae. Here, we describe the characterization of two channelrhodopsins, Volvox channelrhodopsin-1 (VChR1) and VChR2, from the multicellular green alga Volvox carteri. Both are encoded by nuclear single copy genes and are highly expressed in the small biflagellated somatic cells but not in the asexual reproductive cells (gonidia).

An energy balance from absorbed photons to new biomass for Chlamydomonas reinhardtii and Chlamydomonas acidophila under neutral and extremely acidic growth conditions.

Chlamydomonas is one of the most well-studied photosynthetic organisms that had important biotechnological potential for future bioproductions of biofuels. However, an energy balance from incident photons to the energy stored in the new biomass is still lacking. In this study, we applied a recently developed system to measure the energy balance for steady state growth of Chlamydomonas reinhardtii grown at pH 6.

Monitoring light-induced structural changes of Channelrhodopsin-2 by UV-visible and Fourier transform infrared spectroscopy.

Channelrhodopsin-2 (ChR2) is a microbial type rhodopsin and a light-gated cation channel that controls phototaxis in Chlamydomonas. We expressed ChR2 in COS-cells, purified it, and subsequently investigated this unusual photoreceptor by flash photolysis and UV-visible and Fourier transform infrared difference spectroscopy. Several transient photoproducts of the wild type ChR2 were identified, and their kinetics and molecular properties were compared with those of the ChR2 mutant E90Q.

A complete energy balance from photons to new biomass reveals a light- and nutrient-dependent variability in the metabolic costs of carbon assimilation.

The energy balance of Phaeodactylum tricornutum cells from photon to biomass have been analysed under nutrient-replete and N-limiting conditions in combination with fluctuating (FL) and non-fluctuating (SL) dynamic light. For this purpose, the amount of photons absorbed has been related to electrons transported by photosystem II, to gas exchange rates, and to the newly formed biomass differentially resolved into carbohydrates, proteins, and lipids measured by means of Fourier transform infrared (FTIR) spectroscopy. Under high nutrient conditions, the quantum efficiency of carbon-related biomass production (Phi(C)) and the metabolic costs of carbon (C) production were found to be strongly controlled by the light climate.

The application of micro-FTIR spectroscopy to analyze nutrient stress-related changes in biomass composition of phytoplankton algae.

Micro-Fourier transform infrared (FTIR) spectroscopy was used to study changes in spectral features of three species of Cyanobacteria (Microcystis aeruginosa, Croococcus minutus, and Nostoc sp.) and two Bacillariophyceae (Cyclotella meneghiniana, and Phaeodactylum tricornutum) in response to nutrient stress. The change of physiological state of the cells was followed during a 4-week starvation period on the basis of physiological key parameters and by means of FTIR spectroscopy.

Fourier transform infrared spectroscopy as a new tool to determine rosmarinic acid in situ.

A new procedure has been developed for the in situ FT-IR determination of rosmarinic acid (RA) in suspension cultures of Lavandula officinalis. The method involves sample preparation on ZnSe crystals or microplates from silicon, and measuring absorbance spectra between 4000 and 700 cm(-1). First derivative spectra were analysed after normalisation using partial least square (PLS) algorithm.