• Journal of Microbiology and Biotechnology
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• 제15권5호
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• pp.1115-1119
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• 2005

The photoheterotrophic $H_2$ production of Rhodobacter sphaeroides was significantly increased through disruption of the genes coding for uptake hydrogenase and poly-${\beta}$-hydroxybutyrate (PHB) synthase (Lee et al., Appl. Microbiol. Biotechnol. 60: 147-153, 2002). In this work, we further removed the B800-850 light-harvesting (LH) complex from the strain and found an increase in $H_2$ production at the light-saturating cell growth (${\ge}10$ Watts $[W]/m^2$). Neither the mutant nor the wild-type produced more $H_2$ at the brighter light. Accordingly, light does not appear to be limited for the $H_2$ production by the presence of B800-850. However, increase in the level of the spectral complexes resulted in decrease of $H_2$ production. Thus, although the B875 is essential for light harvesting, the consumption of cellular energy for the synthesis of B800-850 and the surplus LH complexes may reduce the energy flow into the $H_2$ production of R. sphaeroides.

• Bulletin of the Korean Chemical Society
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• 제33권3호
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• pp.933-940
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• 2012

Recently, it has been shown that quantum coherence appears in energy transfers of various photosynthetic lightharvesting complexes at from cryogenic to even room temperatures. Because the photosynthetic systems are inherently complex, these findings have subsequently interested many researchers in the field of both experiment and theory. From the theoretical part, simplified dynamics or semiclassical approaches have been widely used. In these approaches, the quantum-classical Liouville equation (QCLE) is the fundamental starting point. Toward the semiclassical scheme, approximations are needed to simplify the equations of motion of various degrees of freedom. Here, we have adopted the Poisson bracket mapping equation (PBME) as an approximate form of QCLE and applied it to find the time evolution of the excitation in a photosynthetic complex from marine algae. The benefit of using PBME is its similarity to conventional Hamiltonian dynamics. Through this, we confirmed the coherent population transfer behaviors in short time domain as previously reported with a more accurate but more time-consuming iterative linearized density matrix approach. However, we find that the site populations do not behave according to the Boltzmann law in the long time limit. We also test the effect of adding spurious high frequency vibrations to the spectral density of the bath, and find that their existence does not alter the dynamics to any significant extent as long as the associated reorganization energy is changed not too drastically. This suggests that adopting classical trajectory based ensembles in semiclassical simulations should not influence the coherence dynamics in any practical manner, even though the classical trajectories often yield spurious high frequency vibrational features in the spectral density.