Oxygenic photosynthesis synthesizes sugars from water and carbon dioxide using light energy from the sun, thereby converts light energy into chemical energy and provides oxygen for aerobic life on the earth. The light-harvesting, electron transfer, and water-splitting reactions of photosynthesis are catalyzed by two large membrane-protein complexes photosystem II (PSII) and photosystem I (PSI). Through high-resolution crystal structural analysis by synchrotron X-rays as well as femtosecond X-ray free electron lasers, the mechanisms of these reactions have become understandable at the atomic level. Here we review the recent progresses in analyzing the structures of PSII and PSI as well as their functional implications.
The history of my research career was described in terms of the neuronal mechanisms of learning acquisition and memory retention especially on the classical conditioning beginning from the invertebrate model systems, Hermissenda and Lymnaea, to vertebrate system, senescent rat, for over 40 years. The topics were covered from the basic science such as the intracellular signal transduction mechanisms to the engineering application as the associative learning device related with learning and memory.
In nature, many types of nano-structures are formed spontaneously through the self-assembly of biomolecules. This review article describes recent progress in chemical strategies to design artificial protein and peptide assemblies. C3-symmetric peptide conjugates and viral β-annulus peptide fragments were developed to construct virus-like peptide nanocapsules. Spatiotemporal control of peptide nanofibre growth was also achieved by photocleavage of a DNA-conjugated β-sheet forming peptide.
Aggregation of Dictyostelium discoideum is mediated by chemotaxis towards propagating waves of chemoattractant cAMP. Because the direction of chemoattractant gradient reversed during the wave passage, how unidirectional migration is achieved remains unresolved. Analysis of cell trajectory and the leading edge response, to exogenously applied dynamic gradients indicated that chemotactic response is rectified; i.e. it is suppressed when the attractant concentration is decreasing over time. We suggest that the upper- and lower-bounds of wave speed that allows cells to move only in the front of the wave and not the back is dictated by the timescale of the underlying reaction-diffusion process.
Appropriate and robust behavioral control in a noisy environment is important for the survival of animals. Understanding such robust behavioral control has been an attractive subject in neuroscience research. We addressed this question in the fly brain by investigating optomotor response to noisy optical flow. We found that flies have a robust recognition of optical flow directions and activities of motion sensitive neurons can quantitatively explain the robustness by applying signal classification theory. Our model study suggested that the robustness were ascribed to simple image noise eliminating methods used in the image processing—a Gaussian smoothing and contrast enhancement—.