Properties of nano-graphite ribbons with zigzag edges -- Difference between odd and even legs --

Persistent currents and transport properties are investigated for the nano-graphite ribbons with zigzag shaped edges with paying attention to system length $L$ dependence. It is found that both the persistent current in the isolated ring and the conductance of the system connected to the perfect leads show the remarkable $L$ dependences. In addition, the dependences for the systems with odd legs and those with even legs are different from each other. On the persistent current, the amplitude for the cases with odd legs shows power-low behavior as $L^{-N}$ with $N$ being the number of legs, whereas the maximum of it decreases exponentially for the cases with even legs. The conductance per one spin normalized by $e^2/h$ behaves as follows. In the even legs cases, it decays as $L^{-2}$, whereas it reaches to unity for $L \to \infty$ in the odd legs cases. Thus, the material is shown to have a remarkable property that there is the qualitative difference between the systems with odd legs and those with even legs even in the absence of the electron-electron interaction.Comment: 4 pagaes, 8 figures, LT25 conference proceeding, accepted for publication in Journal of Physics: Conference Serie

Influence of simulated microgravity on the activation of the small GTPase Rho involved in cytoskeletal formation – molecular cloning and sequencing of bovine leukemia-associated guanine nucleotide exchange factor

BACKGROUND: The irregular formation of cytoskeletal fibers in spaceflown experimental cells has been observed, but the disorganization process of fibers is still poorly understood. It is well known that the activation of the small GTPase Rho leads to actin stress fibers assembly. This study was performed to evaluate the effect of simulated microgravity on the activation of Rho that is involved in actin fiber remodeling in cells. RESULTS: Clinorotation influences actin fiber remodeling and its related signaling pathways that involve the small GTPase Rho. Actin stress fiber remodeling was significantly inhibited to a greater extent in cells cultured under clinorotation than in static cultured cells. From the gene and protein expression analyses, we found that the expression level of leukemia-associated Rho guanine nucleotide exchange factor (LARG), which activates Rho, was downregulated under clinorotation. Moreover, we identified the full-length LARG cDNA. The amount of GTP-bound RhoA, that is, the active form of RhoA, decreased under this condition. CONCLUSION: The activation of the small GTPase Rho was influenced by simulated microgravity generated by a three-dimensional (3D) clinostat. Furthermore, the full-length cDNA of bovine LARG, a member of the Rho guanine nucleotide exchange factor (GEF) family, was identified, and its gene expression was observed to be downregulated under clinorotation. This downregulation subsequently resulted in the repression of RhoA activation. These results indicated that the disorganization of the actin fibers was caused by the inhibition of Rho activation by 3D clinorotation

Isolation of TBP-interacting protein (TIP) from a hyperthermophilic archaeon that inhibits the binding of TBP to TATA-DNA

AbstractWe have isolated TBP (TATA-binding protein)-interacting protein (TIP) from cell lysates of a hyperthermophilic archaeon, Pyrococcus kodakaraensis KOD1, by affinity chromatography with TBP-agarose. Based on the internal amino acid sequence information, PCR primers were synthesized and used to amplify the gene encoding this protein (Pk-TIP). Determination of the nucleotide sequence and characterization of the recombinant protein revealed that Pk-TIP is composed of 224 amino acid residues (molecular weight of 25 558) and exists in a dimeric form. BIAcore analyses for the interaction between recombinant Pk-TIP and recombinant Pk-TBP indicated that they interact with each other with an equilibrium dissociation constant, KD, of 1.24–1.46 μM. A gel mobility shift assay indicated that Pk-TIP inhibited the interaction between Pk-TBP and a TATA-DNA. Pk-TIP may be one of the archaeal factors which negatively regulate transcription

Correlation between thermal aggregation and stability of lysozyme with salts described by molar surface tension increment: an exceptional propensity of ammonium salts as aggregation suppressor

Protein aggregation is a critical problem for biotechnology and pharmaceutical industries.Despite the fact that soluble proteins have been used for many applications, our understandingof the effect of the solution chemistry on protein aggregation still remains to be elucidated.This paper investigates the process of thermal aggregation of lysozyme in the presence ofvarious types of salts. The simple law was found; the aggregation rate of lysozyme increasedwith increasing melting temperature of the protein (Tm) governed by chemical characteristicsof additional salts. Ammonium salts were, however, ruled out; the aggregation rates oflysozyme in the presence of the ammonium salts were smaller than the ones estimatedfrom Tm. Comparing with sodium salts, ammonium salts increased the solubility of thehydrophobic amino acids, indicating that ammonium salts adsorb the hydrophobic region ofproteins, which leads to the decrease in aggregation more effectively than sodium salts. Thepositive relation between aggregation rate and Tm was described by another factor such as thesurface tension of salt solutions. Fourier transform infrared spectral analysis showed thatthe thermal aggregates were likely to form b-sheet in solutions that give high molar surfacetension increment. These results suggest that protein aggregation is attributed to the surfacefree energy of the solution

Findings from recent studies by the Japan Aerospace Exploration Agency examining musculoskeletal atrophy in space and on Earth

The musculoskeletal system provides the body with correct posture, support, stability, and mobility. It is composed of the bones, muscles, cartilage, tendons, ligaments, joints, and other connective tissues. Without effective countermeasures, prolonged spaceflight under microgravity results in marked muscle and bone atrophy. The molecular and physiological mechanisms of this atrophy under unloaded conditions are gradually being revealed through spaceflight experiments conducted by the Japan Aerospace Exploration Agency using a variety of model organisms, including both aquatic and terrestrial animals, and terrestrial experiments conducted under the Living in Space project of the Japan Ministry of Education, Culture, Sports, Science, and Technology. Increasing our knowledge in this field will lead not only to an understanding of how to prevent muscle and bone atrophy in humans undergoing long-term space voyages but also to an understanding of countermeasures against age-related locomotive syndrome in the elderly

The Effectiveness of RNAi in Caenorhabditis elegans Is Maintained during Spaceflight

PublishedJournal ArticleResearch Support, N.I.H., ExtramuralResearch Support, Non-U.S. Gov'tThis is the final version of the article. Available from Public Library of Science via the DOI in this record.BACKGROUND: Overcoming spaceflight-induced (patho)physiologic adaptations is a major challenge preventing long-term deep space exploration. RNA interference (RNAi) has emerged as a promising therapeutic for combating diseases on Earth; however the efficacy of RNAi in space is currently unknown. METHODS: Caenorhabditis elegans were prepared in liquid media on Earth using standard techniques and treated acutely with RNAi or a vector control upon arrival in Low Earth Orbit. After culturing during 4 and 8 d spaceflight, experiments were stopped by freezing at -80°C until analysis by mRNA and microRNA array chips, microscopy and Western blot on return to Earth. Ground controls (GC) on Earth were simultaneously grown under identical conditions. RESULTS: After 8 d spaceflight, mRNA expression levels of components of the RNAi machinery were not different from that in GC (e.g., Dicer, Argonaute, Piwi; P>0.05). The expression of 228 microRNAs, of the 232 analysed, were also unaffected during 4 and 8 d spaceflight (P>0.05). In spaceflight, RNAi against green fluorescent protein (gfp) reduced chromosomal gfp expression in gonad tissue, which was not different from GC. RNAi against rbx-1 also induced abnormal chromosome segregation in the gonad during spaceflight as on Earth. Finally, culture in RNAi against lysosomal cathepsins prevented degradation of the muscle-specific α-actin protein in both spaceflight and GC conditions. CONCLUSIONS: Treatment with RNAi works as effectively in the space environment as on Earth within multiple tissues, suggesting RNAi may provide an effective tool for combating spaceflight-induced pathologies aboard future long-duration space missions. Furthermore, this is the first demonstration that RNAi can be utilised to block muscle protein degradation, both on Earth and in space.This work was supported by a Grant-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science, and Technology of Japan, the Japan Society for the Promotion of Science, and “Ground-Based Research Announcement for Space Utilization” promoted by the Japan Space Forum. TE was supported by the Medical Research Council UK (G0801271). NJS was supported by the National Institutes of Health (NIH NIAMS ARO54342). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Coordination of multiple enzyme activities by a single PCNA in archaeal Okazaki fragment maturation

In vitro reconstitution of Okazaki fragment processing shows that DNA polymerase, flap endonuclease and DNA ligase need to simultaneously bind to the same PCNA-sliding clamp molecule during DNA lagging strand replication

Functional phosphatome requirement for protein homeostasis, networked mitochondria, and sarcomere structure in C. elegans muscle

Background: Skeletal muscle is central to locomotion and metabolic homeostasis. The laboratory worm C. elegans has been developed into a genomic model for assessing the genes and signals that regulate muscle development and protein degradation. Past work has identified a receptor tyrosine kinase signalling network that combinatorially controls autophagy, nerve signal to muscle to oppose proteasome based degradation, and extracellular matrix based signals that control calpain and caspase activation. The last two discoveries were enabled by following up results from a functional genomic screen of known regulators of muscle. Recently, a screen of the kinome requirement for muscle homeostasis identified roughly 40% of kinases as required for C. elegans muscle health; 80 have identified human orthologues and 53 are known to be expressed in skeletal muscle. To complement this kinome screen, here we screen most of the phosphatases in C. elegans. Methods: RNAi was used to knockdown phosphatase encoding genes. Knockdown was first conducted during development with positive results also knocked down only in fully developed adult muscle. Protein homeostasis, mitochondrial structure, and sarcomere structure were assessed using transgenic reporter proteins. Genes identified as being required to prevent protein degradation were also knocked down in conditions that blocked proteasome or autophagic degradation. Genes identified as being required to prevent autophagic degradation were also assessed for autophagic vesicle accumulation using another transgenic reporter. Lastly, bioinformatics were used to look for overlap between kinases and phosphatases required for muscle homeostasis and the prediction that one phosphatase was required to prevent MAPK activation was assessed by Western blot. Results: A little over half of all phosphatases are each required to prevent abnormal development or maintenance of muscle. 86 of these phosphatase have known human orthologues, 57 of which are known to be expressed in human skeletal muscle. Of the phosphatases required to prevent abnormal muscle protein degradation, roughly half are required to prevent increased autophagy. Conclusions: A significant portion of both the kinome and phosphatome are required for establishing and maintaining C. elegans muscle health. Autophagy appears to be the mostly commonly triggered form of protein degradation in response to disruption of phosphorylation based signalling. The results from these screens provide measurable phenotypes for analysing the combined contribution of kinases and phosphatases in a multi-cellular organism and suggest new potential regulators of human skeletal muscle for further analysis

The effects of heat stress on morphological properties and intracellular signaling of denervated and intact soleus muscles in rats

The effects of heat stress on the morphological properties and intracellular signaling of innervated and denervated soleus muscles were investigated. Heat stress was applied to rats by immersing their hindlimbs in a warm water bath (42°C, 30 min/day, every other day following unilateral denervation) under anesthesia. During 14 days of experimental period, heat stress for a total of seven times promoted growth‐related hypertrophy in sham‐operated muscles and attenuated atrophy in denervated muscles. In denervated muscles, the transcription of ubiquitin ligase, atrogin‐1/muscle atrophy F‐box (Atrogin‐1), and muscle RING‐finger protein‐1 (MuRF‐1), genes was upregulated and ubiquitination of proteins was also increased. Intermittent heat stress inhibited the upregulation of Atrogin‐1, but not MuRF‐1 transcription. And the denervation‐caused reduction in phosphorylated protein kinase B (Akt), 70‐kDa heat‐shock protein (HSP70), and peroxisome proliferator‐activated receptor γ coactivator‐1α (PGC‐1α), which are negative regulators of Atrogin‐1 and MuRF‐1 transcription, was mitigated. In sham‐operated muscles, repeated application of heat stress did not affect Atrogin‐1 and MuRF‐1 transcription, but increased the level of phosphorylated Akt and HSP70, but not PGC‐1α. Furthermore, the phosphorylation of Akt and ribosomal protein S6, which is known to stimulate protein synthesis, was increased immediately after a single heat stress particularly in the sham‐operated muscles. The effect of a heat stress was suppressed in denervated muscles. These results indicated that the beneficial effects of heat stress on the morphological properties of muscles were brought regardless of innervation. However, the responses of intracellular signaling to heat stress were distinct between the innervated and denervated muscles