The Experts below are selected from a list of 128751 Experts worldwide ranked by ideXlab platform
Hideto Yoshida - One of the best experts on this subject based on the ideXlab platform.
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effect of Apex cone shape and local fluid flow control method on fine particle classification of gas cyclone
Chemical Engineering Science, 2013Co-Authors: Hideto YoshidaAbstract:Abstract The purpose of this report is to study the effects of Apex cone shape and local fluid flow control method on particle separation performance of gas-cyclones. New type of dry cyclone with the movable Apex cone which is covered with special shaped ring indicated cut size movement from 2 to 40 μm. By use of the Apex cone at the inlet of dust box, it is possible to decrease the fluid velocity component in the dust box and to reduce the re-entrainment of particles from the dust box. The cut size indicated the minimum value for the specific height of the Apex cone. The optimum Apex cone height was found for each inlet velocity. It is found that the optimum Apex cone angle is 70 deg. The minimum 50% cut size was obtained by use of this Apex cone angle. From the flow visualization method by use of soap foam, the upward flow and downward flow coexisted on the surface of this special Apex cone. The clear interface between upward flow and downward flow was detected on the Apex cone angle of 70 deg. The effect of secondary flow injection method on particle separation was also examined. It is found that particle collection efficiency increased with an increased secondary flow rate and number of secondary flow injection in the upper cylindrical part of the cyclone. The new optimum injection method was proposed in this study. The particle separation performance and flow visualization results qualitatively supported the 3-dimensional CFD simulation based on the direct method.
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effect of Apex cone shape on fine particle classification of gas cyclone
Powder Technology, 2010Co-Authors: Hideto Yoshida, Kunihiro Fukui, Yusuke Nishimura, Tetsuya YamamotoAbstract:Abstract The purpose of this paper is to study the effects of Apex cone shape on particle separation performance of gas-cyclones by experiment and CFD studies. It is found that the optimum Apex cone angle is 70°. The minimum 50% cut size was obtained by use of this special Apex cone. From the flow visualization method by use of soap foam, the upward flow and downward flow coexisted on the surface of this special Apex cone. The clear interface between upward flow and downward flow was detected on the Apex cone angle of 70°. The effect of the Apex cone angle on particle separation performance decreases under high inlet velocity conditions, because most particles are moving in the area away from the Apex cone. The particle separation performance and flow visualization results qualitatively supported the 3-dimensional CFD simulation based on the direct method.
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effect of Apex cone height on particle classification performance of a cyclone separator
Advanced Powder Technology, 2003Co-Authors: Hideto Yoshida, Yang Kwansik, Satoshi Akiyama, Kunihiro Fukui, Satoru TaniguchiAbstract:Abstract Experimental and simulation studies have been conducted about the effect of Apex cone height on particle separation performance of a cyclone separator. It is found that the effect of an Apex cone is to decrease the cut size and to increase the collection efficiency. The cut size indicates the minimum value for the specific height of the Apex cone. The optimum Apex cone height changes to the lower position as the cyclone inlet velocity increases. When the Apex cone is set to the high position, the resistance of an incoming particle entering to the dust box increases. The low Apex cone position induces a strong upward fluid flow component and increases the number of escaping particles from the dust box. The magnitude of fluid velocity in the upper part of the dust box decreases under the optimum Apex cone height condition. The experimental data agreed with the numerical simulation based on the direct flow calculation method.
Helge B. Bode - One of the best experts on this subject based on the ideXlab platform.
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an uncommon type ii pks catalyzes biosynthesis of aryl polyene pigments
Journal of the American Chemical Society, 2019Co-Authors: Gina L. C. Grammbitter, Maximilian Schmalhofer, Kudratullah Karimi, Yi-ming Shi, Nicholas J. Tobias, Nina Morgner, Michael Groll, Tim A Schoner, Helge B. BodeAbstract:Aryl polyene (APE) pigments are a widely distributed class of bacterial polyketides. So far, little is known about the biosynthesis of these compounds, which are produced by a novel type II polyketide synthase (PKS). We have identified all enzymes involved in APE biosynthesis and determined their peculiar functions. The biosynthesis was reconstituted in vitro, and ACP-bound intermediates were assigned for each reaction step by HPLC-MS. Native mass spectrometry experiments identified four stable complexes: the acyl-carrier proteins ApeE and ApeF bound to the thioesterase ApeK, the dehydratases ApeI and ApeP, and the ketosynthase ApeO in complex with its chain-length factor ApeC. X-ray structures of the heterodimeric ApeO:ApeC and ApeI:ApeP complexes depict striking protein–protein interactions. Altogether, our study elucidated mechanistic aspects of APE biosynthesis that unifies elements of type II fatty acid and PKS systems, but in addition includes novel enzyme complexes.
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An Uncommon Type II PKS Catalyzes Biosynthesis of Aryl Polyene Pigments
2019Co-Authors: Gina L. C. Grammbitter, Maximilian Schmalhofer, Kudratullah Karimi, Yi-ming Shi, Tim A. Schöner, Nicholas J. Tobias, Nina Morgner, Michael Groll, Helge B. BodeAbstract:Aryl polyene (APE) pigments are a widely distributed class of bacterial polyketides. So far, little is known about the biosynthesis of these compounds, which are produced by a novel type II polyketide synthase (PKS). We have identified all enzymes involved in APE biosynthesis and determined their peculiar functions. The biosynthesis was reconstituted in vitro, and ACP-bound intermediates were assigned for each reaction step by HPLC-MS. Native mass spectrometry experiments identified four stable complexes: the acyl-carrier proteins ApeE and ApeF bound to the thioesterase ApeK, the dehydratases ApeI and ApeP, and the ketosynthase ApeO in complex with its chain-length factor ApeC. X-ray structures of the heterodimeric ApeO:ApeC and ApeI:ApeP complexes depict striking protein–protein interactions. Altogether, our study elucidated mechanistic aspects of APE biosynthesis that unifies elements of type II fatty acid and PKS systems, but in addition includes novel enzyme complexes
Bruce Demple - One of the best experts on this subject based on the ideXlab platform.
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key role of a downstream specificity protein 1 site in cell cycle regulated transcription of the ap endonuclease geneape1 Apexin nih3t3 cells
Journal of Biological Chemistry, 2001Co-Authors: Hua Fung, Richard A Bennett, Bruce DempleAbstract:Abstract Abasic (apurinic/apyrimidinic or AP) sites are a frequent type of DNA damage that threatens genetic stability. The predominant mammalian enzyme initiating repair of AP sites is the Ape1 AP endonuclease (also called Apex or Hap1), which also facilitates DNA binding by several transcription factors (Ref1 activity). We found that expression of the APE1 gene was coordinated with the cell cycle in murine NIH3T3 cells: APE1 mRNA levels rose after the G1-S transition and peaked ∼4-fold higher in early to mid-S phase. The increased APE1 mRNA was the result of transcriptional activation rather than increased mRNA stability. Fusions of various APE1 promoter fragments to the chloramphenicol acetyltransferase CAT reporter gene indicated that APE1 expression depends on two transcription factor Sp1 binding sites within the promoter region. Mutation of these sites or of two CCAAT elements within the APE1 promoter, in conjunction with protein binding studies, demonstrated their specific roles. The Sp1 site upstream of the transcription start, together with an adjacent CCAAT element, establishes a protein-DNA complex required for basal transcription of APE1. The Sp1 site downstream of the transcription start was required for the response to cell growth. Because Ape1 is a dual function enzyme, its cell cycle-dependent expression might affect both DNA repair and the activity of various transcription factors as a function of the cell cycle.
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dynamics of the interaction of human apurinic endonuclease ape1 with its substrate and product
Journal of Biological Chemistry, 1998Co-Authors: Yuji Masuda, Richard A O Bennett, Bruce DempleAbstract:We investigated the interaction dynamics of human abasic endonuclease, the Ape1 protein (also called Ref1, Hap1, or Apex), with its DNA substrate and incised product using electrophoretic assays and site-specific amino acid substitutions. Changing aspartate 283 to alanine (D283A) left 10% residual activity, contrary to a previous report, but complementation of repair-deficient bacteria by the D283A Ape1 protein was consistent with its activity in vitro. The D308A, D283/D308A double mutant, and histidine 309 to asparagine proteins had 22, 1, and ∼0.02% of wild-type Ape1 activity, respectively. Despite this range of enzymatic activities, all the mutant proteins had near-wild-type binding affinity specific for DNA containing a synthetic abasic site. Thus, substrate recognition and cleavage are genetically separable steps. Both the wild-type and mutant Ape1 proteins bound strongly to the enzyme incision product, an incised abasic site, which suggested that Ape1 might exhibit product inhibition. The use of human DNA polymerase β to increase Ape1 activity by eliminating the incision product supports this conclusion. Notably, the complexes of the D283A, D308A, and D283A/D308A double mutant proteins with both intact and incised abasic DNA were significantly more stable than complexes containing wild-type Ape1, which may contribute to the lower turnover numbers of the mutant enzymes. Wild-type Ape1 protein bound tightly to DNA containing a one-nucleotide gap but not to DNA with a nick, consistent with the proposal that substrate recognition by Ape1 involves a space bracketed by duplex DNA, rather than mere flexibility of the DNA.
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excision of c 4 oxidized deoxyribose lesions from double stranded dna by human apurinic apyrimidinic endonuclease ape1 protein and dna polymerase β
Journal of Biological Chemistry, 1998Co-Authors: Edy Y Kim, Bruce DempleAbstract:Oxidative damage to DNA deoxyribose generates oxidized abasic sites (OAS) that may constitute one-third of ionizing radiation damage. The antitumor drug bleomycin produces exclusively OAS in the form of C-4-keto-C-1-aldehydes in unbroken DNA strands and 3′-phosphoglycolate esters terminating strand breaks. We investigated whether two human DNA repair enzymes can mediate OAS excision in vitro: Ape1 protein (the main human abasic endonuclease (also called Hap1, Apex, or Ref1)) and DNA polymerase β, which carries out both the abasic excision and the resynthesis steps. We used a duplex oligonucleotide substrate with one main target for bleomycin-induced damage. Ape1 catalyzed effective incision at the C-4-keto-C-1-aldehyde sites at a rate that may be only a few-fold lower than incision of hydrolytic abasic sites at the same location. Consistent with several previous studies, Ape1 hydrolyzed 3′-phosphoglycolates 25-fold more slowly than C-4-keto-C-1-aldehydes. DNA polymerase β excised the 5′-terminal OAS formed by Ape1 incision at a rate similar to its removal of unmodified abasic residues. Polymerase β-mediated excision of 5′-terminal OAS was stimulated by Ape1 as it is for unmodified abasic sites. Escherichia coli Fpg (MutM) protein also excised 5′-terminal OAS, but in our hands, the RecJ protein did not. These observations help define mammalian pathways of OAS repair, point to interactions that might coordinate functional steps, and suggest that still unknown factors may contribute to removal of 3′-phosphoglycolate esters.
Gina L. C. Grammbitter - One of the best experts on this subject based on the ideXlab platform.
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an uncommon type ii pks catalyzes biosynthesis of aryl polyene pigments
Journal of the American Chemical Society, 2019Co-Authors: Gina L. C. Grammbitter, Maximilian Schmalhofer, Kudratullah Karimi, Yi-ming Shi, Nicholas J. Tobias, Nina Morgner, Michael Groll, Tim A Schoner, Helge B. BodeAbstract:Aryl polyene (APE) pigments are a widely distributed class of bacterial polyketides. So far, little is known about the biosynthesis of these compounds, which are produced by a novel type II polyketide synthase (PKS). We have identified all enzymes involved in APE biosynthesis and determined their peculiar functions. The biosynthesis was reconstituted in vitro, and ACP-bound intermediates were assigned for each reaction step by HPLC-MS. Native mass spectrometry experiments identified four stable complexes: the acyl-carrier proteins ApeE and ApeF bound to the thioesterase ApeK, the dehydratases ApeI and ApeP, and the ketosynthase ApeO in complex with its chain-length factor ApeC. X-ray structures of the heterodimeric ApeO:ApeC and ApeI:ApeP complexes depict striking protein–protein interactions. Altogether, our study elucidated mechanistic aspects of APE biosynthesis that unifies elements of type II fatty acid and PKS systems, but in addition includes novel enzyme complexes.
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An Uncommon Type II PKS Catalyzes Biosynthesis of Aryl Polyene Pigments
2019Co-Authors: Gina L. C. Grammbitter, Maximilian Schmalhofer, Kudratullah Karimi, Yi-ming Shi, Tim A. Schöner, Nicholas J. Tobias, Nina Morgner, Michael Groll, Helge B. BodeAbstract:Aryl polyene (APE) pigments are a widely distributed class of bacterial polyketides. So far, little is known about the biosynthesis of these compounds, which are produced by a novel type II polyketide synthase (PKS). We have identified all enzymes involved in APE biosynthesis and determined their peculiar functions. The biosynthesis was reconstituted in vitro, and ACP-bound intermediates were assigned for each reaction step by HPLC-MS. Native mass spectrometry experiments identified four stable complexes: the acyl-carrier proteins ApeE and ApeF bound to the thioesterase ApeK, the dehydratases ApeI and ApeP, and the ketosynthase ApeO in complex with its chain-length factor ApeC. X-ray structures of the heterodimeric ApeO:ApeC and ApeI:ApeP complexes depict striking protein–protein interactions. Altogether, our study elucidated mechanistic aspects of APE biosynthesis that unifies elements of type II fatty acid and PKS systems, but in addition includes novel enzyme complexes
Alice Y. Ting - One of the best experts on this subject based on the ideXlab platform.
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proteomic mapping in live drosophila tissues using an engineered ascorbate peroxidase
Proceedings of the National Academy of Sciences of the United States of America, 2015Co-Authors: Chiaolin Chen, Namrata D. Udeshi, Steven A. Carr, Alice Y. Ting, Thomas Y K Lau, Frederik Wirtzpeitz, Norbert PerrimonAbstract:Characterization of the proteome of organelles and subcellular domains is essential for understanding cellular organization and identifying protein complexes as well as networks of protein interactions. We established a proteomic mapping platform in live Drosophila tissues using an engineered ascorbate peroxidase (Apex). Upon activation, the Apex enzyme catalyzes the biotinylation of neighboring endogenous proteins that can then be isolated and identified by mass spectrometry. We demonstrate that Apex labeling functions effectively in multiple fly tissues for different subcellular compartments and maps the mitochondrial matrix proteome of Drosophila muscle to demonstrate the power of Apex for characterizing subcellular proteomes in live cells. Further, we generate "MitoMax," a database that provides an inventory of Drosophila mitochondrial proteins with subcompartmental annotation. Altogether, Apex labeling in live Drosophila tissues provides an opportunity to characterize the organelle proteome of specific cell types in different physiological conditions.
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engineered ascorbate peroxidase as a genetically encoded reporter for electron microscopy
Nature Biotechnology, 2012Co-Authors: Jeffrey D Martell, Thomas J Deerinck, Yasemin Sancak, Thomas L Poulos, Vamsi K Mootha, Gina E Sosinsky, Mark H Ellisman, Alice Y. TingAbstract:Electron microscopy (EM) is the standard method for imaging cellular structures with nanometer resolution, but existing genetic tags are inactive in most cellular compartments or require light and can be difficult to use. Here we report the development of 'Apex', a genetically encodable EM tag that is active in all cellular compartments and does not require light. Apex is a monomeric 28-kDa peroxidase that withstands strong EM fixation to give excellent ultrastructural preservation. We demonstrate the utility of Apex for high-resolution EM imaging of a variety of mammalian organelles and specific proteins using a simple and robust labeling procedure. We also fused Apex to the N or C terminus of the mitochondrial calcium uniporter (MCU), a recently identified channel whose topology is disputed. These fusions give EM contrast exclusively in the mitochondrial matrix, suggesting that both the N and C termini of MCU face the matrix. Because Apex staining is not dependent on light activation, Apex should make EM imaging of any cellular protein straightforward, regardless of the size or thickness of the specimen.
