“…The fourth (45.6 ± 0.41 ps) and the fifth (230.4 ± 14.9 ps) SADS in Fig. 6b are ascribable to the vibrationally hot S 1 and S 1 states of B880 Bchl a by referring to the previous report 42 . It is interesting to note that the more long-lived triplet component of β-apo-8′-carotenal was not clearly detected in Reβapo in this time regime.…”
Section: Resultssupporting
confidence: 59%
“…9 can be assigned to the T 1 state of B880 Bchl a judging from both the spectral shape and the lifetime 42 . The third EADS (29.7 μs component) shown with solid blue-line can undoubtedly be assigned to the T 1 state of carotenoid in Reβapo judging from the spectral peak around 530 nm and the lifetime 42 , although the spectral amplitude is very low and hence the spectrum becomes noisy. Fig.…”
Section: Resultsmentioning
confidence: 99%
“…According to our previous study on the carotenoidless LH1 complex from Rsp. rubrum strain G9+ 42 , the rate of the intersystem crossing of the T 1 B880 Bchl a to go back to the ground state was determined to be (41.4 μs) −1 . Therefore, the efficiency ( ) of triplet-triplet energy transfer from T 1 B880 Bchl a to β-apo-8′-carotenal can be calculated according to the following Eq.…”
In bacterial photosynthesis, the excitation energy transfer (EET) from carotenoids to bacteriochlorophyll a has a significant impact on the overall efficiency of the primary photosynthetic process. This efficiency can be enhanced when the involved carotenoid has intramolecular charge-transfer (ICT) character, as found in light-harvesting systems of marine alga and diatoms. Here, we provide insights into the significance of ICT excited states following the incorporation of a higher plant carotenoid, β-apo-8′-carotenal, into the carotenoidless light-harvesting 1 (LH1) complex of the purple photosynthetic bacterium Rhodospirillum rubrum strain G9+. β-apo-8′-carotenal generates the ICT excited state in the reconstituted LH1 complex, achieving an efficiency of EET of up to 79%, which exceeds that found in the wild-type LH1 complex.
“…The fourth (45.6 ± 0.41 ps) and the fifth (230.4 ± 14.9 ps) SADS in Fig. 6b are ascribable to the vibrationally hot S 1 and S 1 states of B880 Bchl a by referring to the previous report 42 . It is interesting to note that the more long-lived triplet component of β-apo-8′-carotenal was not clearly detected in Reβapo in this time regime.…”
Section: Resultssupporting
confidence: 59%
“…9 can be assigned to the T 1 state of B880 Bchl a judging from both the spectral shape and the lifetime 42 . The third EADS (29.7 μs component) shown with solid blue-line can undoubtedly be assigned to the T 1 state of carotenoid in Reβapo judging from the spectral peak around 530 nm and the lifetime 42 , although the spectral amplitude is very low and hence the spectrum becomes noisy. Fig.…”
Section: Resultsmentioning
confidence: 99%
“…According to our previous study on the carotenoidless LH1 complex from Rsp. rubrum strain G9+ 42 , the rate of the intersystem crossing of the T 1 B880 Bchl a to go back to the ground state was determined to be (41.4 μs) −1 . Therefore, the efficiency ( ) of triplet-triplet energy transfer from T 1 B880 Bchl a to β-apo-8′-carotenal can be calculated according to the following Eq.…”
In bacterial photosynthesis, the excitation energy transfer (EET) from carotenoids to bacteriochlorophyll a has a significant impact on the overall efficiency of the primary photosynthetic process. This efficiency can be enhanced when the involved carotenoid has intramolecular charge-transfer (ICT) character, as found in light-harvesting systems of marine alga and diatoms. Here, we provide insights into the significance of ICT excited states following the incorporation of a higher plant carotenoid, β-apo-8′-carotenal, into the carotenoidless light-harvesting 1 (LH1) complex of the purple photosynthetic bacterium Rhodospirillum rubrum strain G9+. β-apo-8′-carotenal generates the ICT excited state in the reconstituted LH1 complex, achieving an efficiency of EET of up to 79%, which exceeds that found in the wild-type LH1 complex.
“…At present, such a protective function is generally accepted. In the overwhelming majority of subsequent works, the interaction of BChl and carotenoids was studied in detail (see: [ 3 , 4 , 5 , 6 , 7 ]).…”
The effect of singlet oxygen on light-harvesting (LH) complexes has been studied for a number of sulfur (S+) and nonsulfur (S−) photosynthetic bacteria. The visible/near-IR absorption spectra of the standard LH2 complexes (B800-850) of Allochromatium (Alc.) vinosum (S+), Rhodobacter (Rba.) sphaeroides (S−), Rhodoblastus (Rbl.) acidophilus (S−), and Rhodopseudomonas (Rps.) palustris (S−), two types LH2/LH3 (B800-850 and B800-830) of Thiorhodospira (T.) sibirica (S+), and an unusual LH2 complex (B800-827) of Marichromatium (Mch.) purpuratum (S+) or the LH1 complex from Rhodospirillum (Rsp.) rubrum (S−) were measured in aqueous buffer suspensions in the presence of singlet oxygen generated by the illumination of the dye Rose Bengal (RB). The content of carotenoids in the samples was determined using HPLC analysis. The LH2 complex of Alc. vinosum and T. sibirica with a reduced content of carotenoids was obtained from cells grown in the presence of diphenylamine (DPA), and LH complexes were obtained from the carotenoidless mutant of Rba. sphaeroides R26.1 and Rps. rubrum G9. We found that LH2 complexes containing a complete set of carotenoids were quite resistant to the destructive action of singlet oxygen in the case of Rba. sphaeroides and Mch. purpuratum. Complexes of other bacteria were much less stable, which can be judged by a strong irreversible decrease in the bacteriochlorophyll (BChl) absorption bands (at 850 or 830 nm, respectively) for sulfur bacteria and absorption bands (at 850 and 800 nm) for nonsulfur bacteria. Simultaneously, we observe the appearance of the oxidized product 3-acetyl-chlorophyll (AcChl) absorbing near 700 nm. Moreover, a decrease in the amount of carotenoids enhanced the spectral stability to the action of singlet oxygen of the LH2 and LH3 complexes from sulfur bacteria and kept it at the same level as in the control samples for carotenoidless mutants of nonsulfur bacteria. These results are discussed in terms of the current hypothesis on the protective functions of carotenoids in bacterial photosynthesis. We suggest that the ability of carotenoids to quench singlet oxygen (well-established in vitro) is not well realized in photosynthetic bacteria. We compared the oxidation of BChl850 in LH2 complexes of sulfur bacteria under the action of singlet oxygen (in the presence of 50 μM RB) or blue light absorbed by carotenoids. These processes are very similar: {[BChl + (RB or carotenoid) + light] + O2} → AcChl. We speculate that carotenoids are capable of generating singlet oxygen when illuminated. The mechanism of this process is not yet clear.
“…Rhodospirillum rubrum has the ability to treat organic wastewater and to recover and reuse bacterial resources such as biomass, single cell protein, bacterial chlorophyll, carotenoids (Dadak et al 2016;Uragami et al 2020). Therefore, R. rubrum treatment for DMW can avoid the secondary pollution of excess sludge to the environment.…”
Rhodospirillum rubrum (R. rubrum) water treatment technology could recycle bio-resource. However, the inability to degrade macromolecular organics limited its wide application. This paper discussed the feasibility of small molecular carbon source promoting R. rubrum directly treatment dairy machining wastewater (DMW) and accumulations for single cell protein and pigment, and establishment of mathematical model. Six small molecules promoted the degradation of macromolecules (proteins) in DMW. They promoted protease secretion and non growth matrix (protein) decomposition in DMW through co metabolism. Among, 550 mg/L potassium sodium tartrate was the best, protease activity and protein removal rate were increased by 100% comparing with control. Then, chemical oxygen demand (COD) and protein removal rates reached 80%, the single cell protein, carotenoid and bacterial chlorophyll yields were increased 2 times. Meanwhile, carbon nitrogen ratio (C/N), food microbial ratio (F/M) were identified as the most important factor by principal component analysis. Multivariate nonlinear equation model between COD removal rate and C/N, F/M, time was established.
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