Non-isothermal crystallization kinetics of chalcogenide Se79Te20Pb1 glass using differential scanning calorimetry technique

In the present paper, the overall amorphous-crystallization transformation kinetics of chalcogenide Se79Te20Pb1 alloy has been reported using differential scanning calorimetry technique under non-isothermal conditions at three different heating rates (5, 10 and 15 °C/min). Amorphous nature of the investigated alloy is verified using X-ray diffraction. The glass transition region has been investigated using three empirical approaches and consonance of these methods has been discussed. The apparent activation energy for glass transition and crystallization region has been deduced using different methods. The Avrami exponent of the investigated alloy indicates one dimension growth of the investigated glass. The deduced values of Hruby’s parameter and fragility index indicate that amorphous alloy has been formed from good glass forming liquids

Some Studies on Control Theory Involving Schrodinger Group

In this M.Sc. project we have discussed and obtained some results related to optimal control and stability properties on Schrodinger grou

ショウジョウバエのグルタミン作動性シナプスにおけるDisrupted-in-Schizophrenia 1とNeurexinの遺伝学的相互作用

筑波大学 (University of Tsukuba)201

Investigating the protein subcomplexes from a conjugative Type IV Secretion System

Type IV secretion system (T4SS) are versatile nanomachines that enable the efficient transport of substrates in bacteria. In general, they are formed from two major membrane embedded subassemblies: an outer membrane core complex (OMCC) and an inner membrane complex (IMC). The conjugative T4SS encoded by the F plasmid is of particular interest due to its clinical relevance as it facilitates the spread of antibiotic resistance amongst bacterial population. Despite its importance, atomic details of the F-T4SS structure and protein-protein interactions were rudimentary which in turn precludes thorough understanding of how conjugation is orchestrated. Therefore, this thesis aimed to improve knowledge on the F-T4SS by studying the structure of the F-OMCC and investigating other proteins the complex may interact with. After optimising the detergent solubilisation of the F-OMCC expressed from the pED208 F-like plasmid, and improving the purification of the complex, a cryo-EM dataset was collected. Using single particle analysis, the structure was solved with an overall resolution of 3.3 Å. The F-OMCC is formed from two concentric rings which have two distinct symmetries. The outer ring adopts 13-fold symmetry whereas the inner ring showed 17-fold symmetry, together they form a 2.1 MDa complex. The atomic models of TraB, TraK and TraV were built into the structure, and they revealed a unique stoichiometric arrangement. Interestingly, TraV and TraK proteins were found to adopt two different conformations within the outer ring. TraV and TraB were found to accommodate the symmetry mismatch by existing in both F-OMCC rings, and also appeared to confer flexibility. This makes the F-OMCC a dynamic complex which is likely to have important implications in the pilus and T4SS activity during conjugation. The interactions between the F-OMCC and other Tra/Trb proteins were also investigated to decipher how the concerted dynamics of the pilus may be connected to the complex. A potential interaction between F-OMCC and the proteins TraH and TraN was observed by pull-down assays. Furthermore, initial work on TraG found that it seems to assemble as a high order oligomer in solution. The results are reminiscent of a hexameric protein which may be functionally important. Together, the findings of this thesis reveal novel insights into the F-T4SS and its subassemblies. The approach used to purify the F-OMCC and study the interactions will act as the basis of future work on the F-T4SS and is directly applicable to the other protein complexes within the conjugative nanomachine.Open Acces

C-peptide Improves Hyperglycemia-induced Endothelial Redox Balance by Preventing Mitochondrial Oxidative Stress and Enhancing NADPH Synthesis

C-peptide, a by-product of insulin biosynthesis, has been shown to ameliorate diabetes-induced renal impairment. Yet, the mechanisms underlying this protective benefit remain unclear. Our studies have shown that C-peptide improved renal peritubular capillary blood flow and reduced vascular oxidants. NADPH (reduced nicotinamide adenine dinucleotide phosphate), appears to be critical to this effect via the actions of numerous vasoprotective systems. Further, our experiments in type I diabetic mice resulted in a significant reduction in renal endothelial NADPH that is subsequently restored with C-peptide. We hypothesized that C-peptide provides protection to renal cortical endothelial cells during type I diabetes by restoring the activity of glucose-6-phosphate dehydrogenase (G6PD), the principal source of NADPH synthesis. Our data show that renal cortical endothelial cells (RCE) from diabetic mice have diminished G6PD activity and their treatment with C-peptide restores its activity back to control levels. These changes in G6PD activity occurred with concomitant alterations in NADPH. Using 2-D gel electrophoresis of RCE lysate coupled with immunoblotting for G6PD, we demonstrate that diabetic RCEs have a significant increase in G6PD post-translational modification (PTM). C-peptide treatment reduced the magnitude of this PTM in diabetic RCEs, which occurred concomitant to restored G6PD activity. These results suggest that improving the activity of endothelial G6PD, by preventing its PTM, may be a potential mechanism by which C-peptide confers protection to renal cortical endothelial cells during type I diabetes. Hyperglycemia-mediated microvascular damage has been proposed to originate from excessive generation of mitochondrial superoxide in endothelial cells and is the suggested mechanism by which the pathogenesis of diabetes-induced renal damage occurs. To determine whether C-peptide affords protection to renal microvascular endothelial cell mitochondria during hyperglycemia we exposed conditionally immortalized murine renal microvascular endothelial cells (MEC) to low or high glucose (25 mM) media with either C-peptide (6.6 nM) or its scrambled sequence control peptide for 24- or 48-hours. Respiratory control ratio, a measure of mitochondrial electrochemical coupling, was significantly higher in high glucose treated renal MECs treated with C-peptide than those of high glucose alone. C-peptide also restored high glucose-induced renal MEC mitochondrial membrane potential changes back to their basal low glucose state. Moreover, C-peptide prevented the excessive mitochondrial superoxide generation and concomitant reductions in mitochondrial complex I activity that are mediated by the exposure of the renal MECs to high glucose. Together, these data demonstrate that C-peptide protects against high glucose- induced generation of mitochondrial superoxide in renal MECs via restoration of basal mitochondrial function. Although interest in the physiologic benefits of C-peptide has persisted for more than two decades, C-peptide has yet to make its way into standard treatment regimens for various diabetic complications. The findings from our work have provide proof-of-principle evidence in support of the inclusion of C-peptide to the existing therapeutic regimen for treatment of diabetic complications, specifically those related to diabetes-induced renal impairment