Following our recent discovery that non-conjugated acyloxy groups can essentially switch off the intramolecular charge transfer (ICT) state of fucoxanthin if it is at the opposite side of the molecule as the conjugated keto group, we have been searching for a keto-carotenoid, which would have the acyloxy group close to the conjugated keto group. Indeed, there exists a pair of keto-carotenoids, siphonaxanthin and siphonein, that have either no acyloxy group (siphonaxanthin) or an acyloxy group at the same side of the molecule as the keto-group (siphonein). In our new paper recently published in Photosynthesis Research we show that the “acyloxy switch” really works. Depending on the position of the acyloxy group in respect to the conjugated keto group, it can either switch off (acyloxy opposite to keto) or switch on (acyloxy at the same side as keto) the ICT state.
The coronavirus infection touches the work of all of us. Yet, thanks to modern technologies and young group members who know how to use them effectively we have organized a virtual group meeting. Obviously, the spirit of the group is not much affected by the current situation. We will continue this way of communicating the results until we can go back to our offices and labs and have standard group meetings.
A new paper from the group has just appeared online in Photochemical and Photobiological Sciences. Thanks to our colleagues from the University of Cagliari and from the Warsaw University of Life Sciences we got a carotenoid-binding protein that has not yet been studied by ultrafast spectroscopy. It comes from the bacterium Deinococcus radiodurans that is well-known for its ability to sustain high doses of UV radiation essentially without damage. The bacterial cell wall of the bacterium is coated by the S-layer, which contains highly ordered two-dimensional arrays of proteins, which form hexameric complexes binding the carotenoid deinoxanthin (S-layer Deinoxanthin Binding Complex – SDBC). The paper provides the first detailed spectroscopic characterization of this carotenoid, both in solution and bound to SDBC.
Our fresh Ph.D. student, Ivča Šímová, has just returned from the workshop “Optimization of light energy conversion in plants and microalgae”, organized under SE2B in Porto, Portugal. She has presented the first data from her Ph.D. project focused on energy transfer processes in unusual purple bacterial antenna. The recently described antenna system from Gemmatimonas phototrophica featuring antenna having two concentric rings of BChl-a, and so far unknown carotenoid is just such unusual antenna.
After publishing two papers on pump-dump-probe spectroscopy in 2018, we took a short break as the two main persons behind the pump-dump-probe setup (Robert and Valja) left the group. Now, when Valja is back after nearly two-year postdoc stay in the group of Janne Ihalainen in Jyvaskyla, we are reviving the PDP setup again with a hope to reveal new features of excited state dynamics of those fantastic orange molecules – carotenoids. In the new detection setup, the PDP experiment is coupled with the prism spectrometer so we can see the effect of dumping/re-pumping in much broader spectral window than two years ago.
The February issue of BBA-Bioenergetics published our latest contribution to research of OCP and related proteins. This time we join efforts with our colleagues from other labs to combine spectroscopy and structural analysis of two OCP forms, OCP1 and OCP2. From the spectroscopic point of view, the paper shows our first data measured with a prism spectrometer in the detection system allowing to measure transient absorption spectra in the 400-1200 nm spectral region. The data presented in the paper were collected using the setup of our friends at ELI Beamlines, but now we have our own detection with prism spectrometer to run the experiments – our own data will appear soon elsewhere! Of course, we need to give up some spectral resolution in such experimental arrangement, but to see all spectral and dynamical features in the whole 400-1200 nm spectrum is simply fantastic. In the figure bellow you can see an example of the super broadband white-light continuum from our lab generated in a sapphire plate as it is seen at the CCD detector after the prism spectrometer.
The laboratory of Optical Spectroscopy has been founded in 2005 at the Institute of Physical Biology based in Nové Hrady, University of South Bohemia in České Budějovice. December 2013 we have relocated the laboratory to the newly built university facility at the Faculty of Science, University of South Bohemia in České Budějovice. Since then, we had shared sextillions of femtoseconds of happy and exciting moments, and had lightened up many of the research ideas. Here is the short summary of the recent years in photos of social events...