The Emi2 Protein of Saccharomyces cerevisiae is a Hexokinase Expressed under Glucose Limitation

Hexokinases catalyze glucose phosphorylation at the first step in glycolysis in eukaryotes. In the budding yeast Saccharomyces cerevisiae , three enzymes for glucose phosphorylation have long been known: Hxk1, Hxk2, and Glk1. In this study, we focus on Emi2, a previously uncharacterized hexokinase-like protein of S. cerevisiae . Our data show that the recombinant Emi2 protein (rEmi2), expressed in Escherichia coli , possesses glucose-phosphorylating activity in the presence of ATP and Mg ²⁺ . It was also found that rEmi2 phosphorylates not only glucose but also fructose, mannose and glucosamine in vitro . In addition, we examined changes in the level of endogenous Emi2 protein in S. cerevisiae in the presence or absence of glucose and a non-fermentable carbon source. We found that the expression of Emi2 protein is tightly suppressed during proliferation in high glucose, while it is strongly upregulated in response to glucose limitation and the presence of a non-fermentable carbon source. Our data suggest that the expression of the endogenous Emi2 protein in S. cerevisiae is regulated under the control of Hxk2 in response to glucose availability in the environment.     

Preparation and characterization of natural rubber dispersed in nano-matrix

Preparation of a model nano-matrix-dispersed polymer was investigated in terms of graft-copolymerization of deproteinized natural rubber latex with styrene, using tert-butyl hydroperoxide/tetraethylenepentamine as an initiator. The products were characterized by ¹H-NMR spectroscopy and size-exclusion-chromatography after ozonolysis. The grafting efficiency of styrene was found to be more than 90% under the best condition of the graft-copolymerization. The morphology of the film specimens, prepared from graft-copolymers, was observed by transmission electron microscopy after staining the films with OsO₄. Natural rubber particle of about 0.5 μm in diameter was dispersed in polystyrene matrix of about 15 nm in thickness.     

Effect of fatty acids on the strain‐induced crystallization of natural rubber detected by tear energy measurements

The strain‐induced crystallization of natural rubber (NR) was investigated by the measurement of the tear energy of a crosslinked blend consisting of NR and noncrystalline styrene–butadiene rubber (SBR). When NR was dispersed into the SBR matrix, the tear energy of SBR increased at various temperatures and tear rates. After the application of the principle of time–temperature superposition to the tear energy according to the Williams–Landel–Ferry equation, two distinct curves were found for the NR/SBR blend with respect to the reduced tear rate, despite the fact that the tear energy of SBR or the SBR/SBR blend gave its own single composite curve. When the fatty acid in the NR/SBR blend was removed by acetone extraction, the tear energy of the blend drew a single composite curve. The conversion of the two curves into the single composite curve for the NR/SBR blend suggested that the tear energy depended on the strain‐induced crystallization of NR dispersed in the SBR matrix, which was suppressed by the removal of the fatty acid. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 613–619, 2005     

Evaluation of size effect on mechanical properties of singlecrystal silicon by nanoscale bending test using AFM

This paper describes a nanometer-scale bending test for a single crystal silicon (Si) fixed beam using an atomic force microscope (AFM). This research focuses on revealing the size effect on the mechanical property of Si beams ranging from a nano- to millimeter scale. Nanometer-scale Si beams, with widths from 200 to 800 nm and a thickness of 255 nm, were fabricated on an Si diaphragm by means of field-enhanced anodization using AFM and anisotropic wet etching. The efficient condition of the field-enhanced anodization could be obtained by changing the bias voltage and the scanning speed of the cantilever. Bending tests for micro- and millimeter-scale Si beams fabricated by a photolithography technique were also carried out using an ultraprecision hardness tester and scratch tester, respectively. Comparisons of Young's modulus and bending strength, of Si among the nano-, micro-, and millimeter scales showed that the specimen size did not have an influence on the Young's modulus in the (110) direction, whereas it produced a large effect on the bending strength. Observations of the fractured surface and calculations of the clack length from Griffith's theory made it clear that the maximum peak-to-valley distance of specimen surface caused the size effect on the bending strength     

Quantitative analysis for reaction between epoxidized natural rubber and poly (L‐lactide) through 1H‐NMR spectroscopy

Reaction between epoxidized natural rubber and poly(L ‐lactide) (PLLA) was investigated quantitatively in terms of conversion of the epoxidized natural rubber. The epoxidized natural rubber was prepared by epoxidation of high ammonia natural rubber (HA‐NR) or deproteinized natural rubber (DPNR) with peracetic acid followed by depolymerization with ammonium persulfate. The resulting liquid HA‐NR having epoxy group (LENR) or liquid DPNR having epoxy group (LEDPNR) were subjected to heating at 473 K for 20 min, after blending with PLLA. The products were characterized through morphology observation, DSC measurement, and ¹H‐NMR spectroscopy. The conversions of the rubbers were estimated from intensity ratio of signals in ¹H‐NMR spectrum for the products after removing unreacted rubber with toluene. Difference in the estimated conversion between the LENR/PLLA and LEDPNR/PLLA blends was interpreted in relation to proteins present in the rubber. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

First-principles investigation on the segregation of Pd at LaFe1-xPdxO3-y surfaces

First-principles calculations were performed to investigate the effect of Pd concentration and oxygen vacancies on the stability of Pd at LaFeO₃ surfaces. We found a much stronger tendency of Pd to segregate by taking the aggregation of Pd at LaFe_1-xPd_xO_3-y surfaces into consideration, resulting in a pair of Pd-Pd around a vacancy. Moreover, we predicted that one oxygen-vacancy-containing FeO₂-terminated surfaces would be stable at high temperatures by comparing the stability of LaFe_1-xPd_xO_3-y surfaces, which further supports our previous conclusion that a Pd-containing perovskite catalyst should be calcined at 1,073 K or higher temperatures in air to enhance the segregation of Pd in the vicinity of surfaces to rapidly transform the Pd catalyst from oxidized to reduced states on the perovskite support.     

Analysis of genetic interactions between DHH1, SSD1 and ELM1 indicates their involvement in cellular morphology determination in Saccharomyces cerevisiae

The DHH1 gene of Saccharomyces cerevisiae belongs to a family of genes that encode highly conserved DEAD-box proteins commonly present in various eukaryotic organisms. Its precise function in yeast has not yet been well documented. To investigate its role in vivo, we constructed a DHH1 disruptant, characterized it genetically and searched for genes the mutations in which would cause synthetic lethality in combination with the DHH1 disruption. CDC28, ELM1 and SSD1 were thus found to be such candidates and we subsequently analysed their interactions. Mutations in ELM1 were previously reported to result in the elongation of cells. We confirmed this phenotype and observed in addition elongated bud formation in an Elm1p overproducing strain. Also, Elm1p fused with the green fluorescent protein (GFP) was found to be localized at the bud neck. These and other observations seem to suggest that Elm1p plays a role during cytokinesis in S. cerevisiae. The phenotypes of strains harbouring either delta dhh1 delta elm1 or ssd1-d delta elm1 were very similar to each other, showing abnormal cellular morphology and defects in cytokinesis and mitosis. Furthermore, DHH1 and SSD1 could functionally complement each other in the ade2 red colour pigment formation, hypersensitivity to SDS, growth on synthetic media and at high temperature. A triple mutant, delta dhh1 ssd1-d delta elm1, apparently had very fragile cell walls and could grow only in a medium supplemented with 1 M sorbitol.     

P3a of event-related potential in chronic methamphetamine dependence

To investigate the psychophysiological features of methamphetamine (MAP) dependence, we recorded auditory event-related potentials (ERPs) in 15 patients with MAP dependence and in 15 age-matched normal controls. ERPs were recorded during a standard oddball task and a read task similar to those employed by Squires et al. (Squires NK, Squires KC, Hillyard SA [1975] Two varieties of long-latency positive waves evoked by unpredictable auditory stimuli in man. Electroenceph Clin Neurophysiol 38:387-401). The patients with MAP dependence showed reduced P3a amplitude and area in the read task and delayed P3b latency with normal P3b amplitude and area in the oddball task. These results suggest that central noradrenergic dysregulation may persist after the remission of acute psychotic symptoms in MAP psychosis and that chronic MAP dependence would produce impairment of the frontal cortex.     

Detection of serum p53 antibodies in patients with esophageal squamous cell carcinoma: correlation with clinicopathologic features and tumor markers

The significance of serum p53-Abs in patients with esophageal squamous cell carcinoma was determined. Examination of clinicopathological features and assessment of tumor marker sensitivities of carcinoembryonic antigen (CEA), squamous cell carcinoma antigen (SCC-Ag) and CYFRA21-1 were performed. Thirty-three (58%) of 57 patients were positive for serum p53-Abs, however, no relation with cancer progression existed. Fourteen of the 33 sero-positive patients revealed normal levels of all tumor markers tested. Thus, serum p53-Abs appears to be a useful marker for the detection of esophageal squamous cell carcinoma.     

Cloning and heterologous expression of a beta-fructofuranosidase gene from Arthrobacter globiformis IFO 3062, and site-directed mutagenesis of the essential aspartic acid and glutamic acid of the active site

We have cloned the gene encoding a beta-fructofuranosidase from Arthrobacter globiformis IFO 3062, and subsequently, the gene was heterologously expressed in Escherichia coli. This beta-fructofuranosidase gene encodes a protein of 548 amino acid residues with a calculated molecular mass of 60,519 Da. We have examined the roles of three residues of A. globiformis IFO 3062 beta-fructofuranosidase by site-directed mutagenesis, and found that aspartic acid 130 and glutamic acid 392, which are two of the apparent catalytic residues, are essential for hydrolase activity. This study provides the first experimental evidence showing that these two amino acid residues of beta-fructofuranosidase play a critical role in hydrolyzing sucrose.