Conjugates between photosystem I and a carbon nanotube for a photoresponse device

Photosystem I (PS I) is a large pigment–protein complex embedded in the thylakoid membranes that performs light-driven electron transfer across the thylakoid membrane. Carbon nanotubes exhibit excellent electrical conductivities and excellent strength and stiffness. In this study, we generated PSI–carbon nanotube conjugates dispersed in a solution aimed at application in artificial photosynthesis. PS I complexes in which a carbon nanotube binding peptide was introduced into the middle of the PsaE subunit were conjugated on a single-walled carbon nanotube, orienting the electron acceptor side to the nanotube. Spectral and photoluminescence analysis showed that the PS I is bound to a single-walled carbon nanotube, which was confirmed by transmission electron microscopy. Photocurrent observation proved that the photoexcited electron originated from PSI and transferred to the carbon nanotube with light irradiation, which also confirmed its orientated conjugation. The PS I–carbon nanotube conjugate will be a useful nano-optoelectronic device for the development of artificial systems.     

A new method for determination of parity in optical diffraction patterns from the structures with helical symmetry

In optical diffraction patterns from the structures with helical symmetry, the reflections appear as layer-lines. The Bessel function orders (n) of the layer-lines are not easily determined, because the radial co-ordinates of the principal maxima on the layer-lines cannot be measured precisely. We developed a method to find whether n is even or odd (parity of n) by superposing two identical images of a particle back to back with the two axes aligned. The method was successfully applied to analysis of the structure of straight polyhooks isolated from the mutant SJW880 of Salmonella typhimurium.     

Functional conservation and divergence of BMP ligands in limb development and lipid homeostasis of holometabolous insects

Bone morphogenetic protein (BMP) ligands play key roles in regulating morphological and physiological traits. To investigate how the functions of BMP ligands have evolved among insects, the roles of two key BMP ligands, decapentaplegic (dpp) and glass bottom boat (gbb), were studied in the flour beetle, Tribolium castaneum. RNA interference‐mediated knockdown revealed that the role of dpp in establishing limb segmentation is conserved among insects. Based on the expression pattern of dpp in the presumptive leg tarsal segments, we propose that the function of dpp has evolved through heterochronic changes during the evolution of complete metamorphosis. Gbb1 was found to be necessary for sculpting the tarsal segment morphology characteristic of beetles. Knockdown of Dpp and Gbb1 expression also resulted in transparent larvae and reduced triglyceride levels, indicating their critical roles in maintaining lipid homeostasis. Both knockdown phenotypes were mediated by larval translucida. Because only Gbb regulates lipid metabolism in Drosophila, regulation of lipid homeostasis appears to have evolved by developmental systems drift. Thus, developmental systems drift may underlie evolution of both morphology and physiological processes.     

Dynamic property of intermediate filaments: Regulation by phosphorylation

Site-specific phosphorylation of intermediate filament (IF) proteins on serine and threonine residues leads to alteration of the filament structure, in vitro and in vivo. Protein kinases involved in cell signaling and those activated in mitosis dynamically control spatial and temporal organization of intracellular IF phosphorylation. Thus, IF phosphorylation appears to be one of the most predominant strategies in coordinating intracellular organization of the IF network.