Photosystems are natural energy conversion systems evolved for over 2,700 million years. Among the photosystems, photosystem II (PSII) catalyzes the light-driven water decomposition reaction with the production of O2, protons and electrons to reduce plastoquinone. The reaction is important not only for understanding natural photosynthesis but also for creating efficient artificial photosynthesis. In this review, PSII catalytic intermediate states and their reaction mechanisms elucidated by experimental and theoretical approaches are introduced mainly following the development of the X-ray crystallography. For the O2 formation mechanism, two representative mechanisms, acid-base and radical coupling, are explained. Finally, we discuss the geometrical and electronic structures of inorganic model complex in comparison with those of the native catalytic center in PSII.
Macroscopic ordering is key in multicellular behaviors, but its predictive understanding has been challenging since the dynamics are typically out of equilibrium. Here we show that mouse neural progenitor cells cultured on dish present features of an active nematic system, resembling the patterns of liquid crystal but with the cells rapidly gliding and stochastically switching its velocity. We found through live imaging that the topological defects behave as sources and sinks of the cell density and results in 3D aggregates. This phenomenon can be theoretically explained by considering the coupling of the anisotropic friction and the active collective force field around the defects.
In this review, the recent advances in neural control engineering are described in terms of three hierarchical levels. In the lowest level, the microelectrode recording and electromagnetic stimulation technique are particularly addressed. In the middle level, two types of neural stimulation and their evoked responses in the rodent auditory cortex are explained on our experimental results using flavoprotein autofluorescence imaging. In the highest level, finally, one of our computational models for the auditory cortex is introduced to simulate auditory induction phenomenon and the associated sound-driven responses.
KCNQ1 is a voltage-gated K+ channel. Its gating property is dramatically changed by an auxiliary subunit KCNE1: the gating kinetics becomes almost 100 times slower and the voltage dependence (G-V curve) is shifted by +40 mV. It is still not perfectly understood how KCNE1 slows or inhibits the opening of KCNQ1 channel. Recent applications of voltage clamp fluorometry (VCF) has been elucidating many aspects of the gating in KCNQ1-KCNE1 channels. KCNE1 directly interacts with voltage sensing domain (VSD) of KCNQ1 channel and prevents VSD from going upward. As a consequence, KCNQ1-KCNE1 channels requires higher membrane potential to overcome the hindrance.