Photosynthetic reaction center is a membrane proteinwhich plays an important role in converting solar energy intochemical energy. Upon continuous illumination a chargeseparation occurs within the protein which is stable forseveral seconds . The stability of this state is veryimportant to protect the protein against the release of excessheat and an instable radical due to charge recombination.Absorption of terahertz radiation corresponds to theexcitation of large vibrations in the protein and is thus suitablefor studying its different dynamical states. Here we recordedterahertz absorption spectra of the dark and illuminated stateof reaction centre from the purple membrane bacteriaRhodobacter sphaeroidesto investigate the stability of thecharge separated state. The difference terahertz absorptionspectra show an overall increase in absorption for theilluminated state in the 30-130 cm-1spectral region. Bysimulating and fitting a theoretical terahertz spectrum ofreaction center from an elastic network model we were able toinvestigate the effect of charge separation and conformationalchanges within the interaction network. We find that a moreloose interaction network in the photoactivated state of theprotein is the most probable cause of the absorption increase.
|Number of pages||1|
|Publication status||Published - 2012|