The bacterial flagellar filament is a helical propeller for the rapid swimming of bacteria. Its gently curved and twisted tubular structure is made of a single protein, flagellin, by its self-assembly in a helical manner. The mechanism for the formation of the left-handed helical tube for swimming and its dynamic polymorphic transition into right-handed forms for tumbling in response to quick reversal of the motor rotation has been revealed in the filament and protofilament structures at atomic detail obtained by convergent application of electron cryomicroscopy, X-ray fiber diffraction and X-ray crystallography with new technological devices in each of these methods.
Caenorhabditis elegans is expected to be the first multicellular organism whose embryogenesis is fully reconstructed on the computer. To achieve this goal, technologies for high-throughput quantitative data collection, systematic model generation, and large-scale 3-dimensional simulation are needed to be developed. We have developed a system that automatically acquires early embryonic cell lineage of C. elegans. We have also developed a 'finite element method' based simulation tool for microtubule dependent sperm pronucleus movement in early C. elegans embryo. Those technologies will help us to develop system level understanding of C. elegans embryo.
In 1969, the first antifreeze protein (AFP) was discovered from the blood plasma of Antarctic Nototheniids. In the past thirty years, different types of AFP have been found in many life forms that exhibit freezing tolerance, such as bacteria, fungi, plants, insects, and vertebrates. These discoveries have evoked us many questions regarding to the antifreeze mechanism and its biological significance for preventing their tissues from freezing damage. At present, ice physicist, biologist, chemist, biochemist, molecular biologist, physiologist, and NMR and X-ray structural biologists are subjecting AFP, which greatly improves our understandings about AFP and accelerates its applicability to various cryo-industries. In the present review we will describe an updated biophysical aspects of AFP to highlight the interests of this research field.
Morphology and local mechanical properties of sheared endothelial cells were measured by using atomic force microscope. After applying a steady shear stress of 2 Pa for 6 hours, bovine aortic endothelial cells showed marked elongation and aligned in the flow direction. The peak cell height decreased significantly with exposure to fluid flow. The fluorescent images showed that control cells exhibited dense peripheral bands of F-actin filaments, while sheared cells exhibited F-actin stress fibers which were thick and centrally located parallel to the flow direction. Elastic modulus estimated by the Hertz model significantly increased with fluid shear stress. Change in mechanical properties might be closely correlated to the development of cytoskeletal structure.