Interactions between colloidal silver and photosynthetic pigments located in cyanobacteria fragments and in solution

Heavy Metals Effect on Cyanobacteria Synechocystis aquatilis Study Using Absorption, Fluorescence, Flow Cytometry, and Photothermal Measurements

“…Therefore, the relative MFC values are sensitive to changes in the emission intensity, while the relative values of Φ F of the sample and the reference bring information on the source of the changes and describe then quantitatively. As follows from an analysis of the results (Table 1), for excitation in the Chl Soret band, the relative yield of fluorescence higher than unity can be related to deaggregation of the dyes or their complexes with proteins and/or to enhancement of the pigment's emission as a result of plasmon generation (observed earlier for some concentrations of Ag ions in Synechocystis [29]). The ratio of Φ F of the sample studied and the reference lower than unity (Table 1) mean smaller areas under the fluorescence curves and/or absorbance and suggest disturbances in the energy transfer between phycobilisomes and Chl.…”

“…The ratio of Φ F of the sample studied and the reference lower than unity (Table 1) mean smaller areas under the fluorescence curves and/or absorbance and suggest disturbances in the energy transfer between phycobilisomes and Chl. Finally, it can be concluded that the emission could be quenched as a consequence of interactions with the ions [29] and/or damaged phycobilisomes can lead to disappearance of their fluorescence caused by the response of cyanobacteria to strong toxicity of metal ions in their environment. It seems that cytometry is more sensitive as it shows that even moderate stress (intermediate ion concentrations) disturbing the electron transfer and the photochemical reaction (according to the mechanism proposed [22]) can be manifested by greater loss of the energy absorbed via fluorescence (when heat emission is relatively constant, see Fig.…”

Interplay between gold nanoparticle biosynthesis and metabolic activity of cyanobacteriumSynechocystissp. PCC 6803

“…For a detailed analysis we recorded the UV-vis extinction spectra of the cyanobacteria culture before (figure 1(a) curve a) and after exposure (figure 1(a) curve b) for 24 h to the gold ions. The spectrum recorded before cell exposure exhibits two absorption bands corresponding to pigments chl a and phycobilisomes (PBS) present in cyanobacteria cells (at 680 and 630 nm, respectively), as well as to carotenoids (or similar pigments) and chl a Soret region at 445 nm [22]. Notably, the spectrum recorded after cell exposure to gold ions exhibits along to previously discussed bands, a new absorption band which emerges at 522 nm and can be assigned to surface plasmon resonance-the specific optical signature of GNPs (see for comparison the UV-vis spectrum of pure colloidal GNPs in figure 1(a) curve c) [23].…”

Estudo da ação combinada de radiações ionizantes com campos elétricos e magnéticos em cianobactérias - viabilidade celular e atenuação de toxinas.

“…Seus pigmentos são compostos principalmente pela clorofila a (algumas possuem a clorofila b ou d) e por ficobilinas, além de carotenos e xantofilas (BEUTLER, 2003;LEE, 2008;SIEJAK;FRACKOWIAK, 2007 ALVES; WHITTON;POTTS, 2000).…”