We demonstrate a way to conjugate a light-harvesting complex, peridinin-chlorophyll-protein, with silver nanowires using biotin-streptavidin linker. In the case of conjugated structure we observe slight increase of the fluorescence intensity of the chlorophyll emission followed by the gradual decrease of the intensity due to photobleaching. For a non-conjugated mixture of peridinin-chlorophyll-protein with silver nanowires only the photobleaching takes place. The results suggest a possible way to fabricate hybrid nanostructures comprising light-harvesting complexes and metallic nanoparticles for achieving the efficient plasmon-induced enhancement of absorption of the light-harvesting complexes.
We study the effect of plasmon excitations in silver island film on the optical properties of peridinin-chlorophyll-protein light-harvesting complex using scanning fluorescence microscopy. With this technique we can unambiguously locate areas where the biomolecules are deposited on the metallic nanostructures from the areas where they stick to the glass surface. The enhancement factor of fluorescence intensity obtained for such a hybrid nanostructure is found to be 3. Plasmon excitations in the SIF layer also influence the dynamics of the emission, but in this case the interpretation of the results is more complex.
Most ultrafast transient absorption studies of primary electron transfer in reaction centers from purple bacteria have been performed in complexes isolated from their natural lipid membrane environment using detergent. In this contribution we present near-UV-vis transient absorption studies of reaction centers embedded in their natural membrane environment. The evolution of absorption spectra recorded with subpicosecond resolution and reflecting primarily electron transfer reactions has been compared to data obtained previously for isolated reaction centers. We conclude that the overall spectral evolution in both types of samples is similar, and the environment of the reaction center protein has only a minor effect on the primary electron transfer reactions. The differences between the two samples are explained in terms of different energetic levels (and their different temporal evolution) of the two initial charge separated states P^+B_A^- and P^+H_A^-, with P being the primary electron donor and B_A and H_A the two consecutive electron acceptors. Additionally, in the electric field generated by P^+H_A^-, B_A in membrane-bound reaction centers undergoes a stronger electrochromic shift than in isolated reaction centers.
A brief survey is given on the elementary reactions of photosynthesis, with an emphasis on the functional separation into reaction centers that perform, after excitation, an ultrafast charge separation across the photosynthetic membrane, and light-harvesting complexes that absorb light and transfer the excitation energy to the reaction centers. The basic concepts are compared to those of photovoltaics.
Human skin contains various types of native fluorophores and absorbers with unique absorption and emission spectra, different quantum efficiency, concentration and spatial distribution within the skin. Autofluorescence spectroscopy is applied as diagnostic tool for cutaneous tumor detection that increases the importance of evaluation of natural existing fluorophores and unification of data for given class of pathologies. In the current study, several excitation sources in the region 337-405 nm are applied, to achieve information about typical autofluorescent properties of normal human skin.
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