The Experts below are selected from a list of 87 Experts worldwide ranked by ideXlab platform
Su Xiao-dong - One of the best experts on this subject based on the ideXlab platform.
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Get Phases from Arsenic Anomalous Scattering: de novo SAD Phasing of Two Protein Structures Crystallized in Cacodylate Buffer
plos one, 2011Co-Authors: Liu Xiang, Zhang Heng, Wang Xiao-jun, Li Lan-fen, Su Xiao-dongAbstract:The crystal structures of two proteins, a putative pyrazinamidase/nicotinamidase from the dental pathogen Streptococcus mutans (SmPncA) and the human caspase-6 (Casp6), were solved by de novo arsenic single-wavelength anomalous diffraction (As-SAD) phasing method. Arsenic (As), an uncommonly used element in SAD phasing, was covalently introduced into proteins by Cacodylic Acid, the buffering agent in the crystallization reservoirs. In SmPncA, the only cysteine was bound to dimethylarsinoyl, which is a pentavalent arsenic group (As (V)). This arsenic atom and a protein-bound zinc atom both generated anomalous signals. The predominant contribution, however, was from the As anomalous signals, which were sufficient to phase the SmPncA structure alone. In Casp6, four cysteines were found to bind cacodyl, a trivalent arsenic group (As (III)), in the presence of the reducing agent, dithiothreitol (DTT), and arsenic atoms were the only anomalous scatterers for SAD phasing. Analyses and discussion of these two As-SAD phasing examples and comparison of As with other traditional heavy atoms that generate anomalous signals, together with a few arsenic-based de novo phasing cases reported previously strongly suggest that As is an ideal anomalous scatterer for SAD phasing in protein crystallography.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000294686100025&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Multidisciplinary SciencesSCI(E)PubMed6ARTICLE9e24227
Xiao-jun Wang - One of the best experts on this subject based on the ideXlab platform.
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A putative three-stage cysteine modification mechanism for SmPncA.
2013Co-Authors: Xiang Liu, Heng Zhang, Xiao-jun WangAbstract:In stage 1, proton abstraction by Asp9 would increase the nucleophilicities of Cys136 and facilitate nucleophilic attack at Cacodylic Acid (CAD); Proton donation from Asp9 to the hydroxyl group of the CAD would promote As-O bond cleavage and release of H2O as the intermediate in stage 2 collapses to give a dimethylarsinoyl fixed Cys136 in stage 3.
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Anomalous difference Fourier map calculated with final phases at 5 σ.
2013Co-Authors: Xiang Liu, Heng Zhang, Xiao-jun WangAbstract:A. Atoms are shown as sticks model, and colored as follows: carbon, green; oxygen, red; nitrogen, blue; zinc, grey; arsenic, purple. B. The Casp6 structure is shown as a backbone representation. The cysteines modified by Cacodylic Acid are presented in the model.
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Get phases from arsenic anomalous scattering: de novo SAD phasing of two protein structures crystallized in cacodylate buffer.
PloS one, 2011Co-Authors: Xiang Liu, Heng Zhang, Xiao-jun WangAbstract:The crystal structures of two proteins, a putative pyrazinamidase/nicotinamidase from the dental pathogen Streptococcus mutans (SmPncA) and the human caspase-6 (Casp6), were solved by de novo arsenic single-wavelength anomalous diffraction (As-SAD) phasing method. Arsenic (As), an uncommonly used element in SAD phasing, was covalently introduced into proteins by Cacodylic Acid, the buffering agent in the crystallization reservoirs. In SmPncA, the only cysteine was bound to dimethylarsinoyl, which is a pentavalent arsenic group (As (V)). This arsenic atom and a protein-bound zinc atom both generated anomalous signals. The predominant contribution, however, was from the As anomalous signals, which were sufficient to phase the SmPncA structure alone. In Casp6, four cysteines were found to bind cacodyl, a trivalent arsenic group (As (III)), in the presence of the reducing agent, dithiothreitol (DTT), and arsenic atoms were the only anomalous scatterers for SAD phasing. Analyses and discussion of these two As-SAD phasing examples and comparison of As with other traditional heavy atoms that generate anomalous signals, together with a few arsenic-based de novo phasing cases reported previously strongly suggest that As is an ideal anomalous scatterer for SAD phasing in protein crystallography.
Liu Xiang - One of the best experts on this subject based on the ideXlab platform.
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Get Phases from Arsenic Anomalous Scattering: de novo SAD Phasing of Two Protein Structures Crystallized in Cacodylate Buffer
plos one, 2011Co-Authors: Liu Xiang, Zhang Heng, Wang Xiao-jun, Li Lan-fen, Su Xiao-dongAbstract:The crystal structures of two proteins, a putative pyrazinamidase/nicotinamidase from the dental pathogen Streptococcus mutans (SmPncA) and the human caspase-6 (Casp6), were solved by de novo arsenic single-wavelength anomalous diffraction (As-SAD) phasing method. Arsenic (As), an uncommonly used element in SAD phasing, was covalently introduced into proteins by Cacodylic Acid, the buffering agent in the crystallization reservoirs. In SmPncA, the only cysteine was bound to dimethylarsinoyl, which is a pentavalent arsenic group (As (V)). This arsenic atom and a protein-bound zinc atom both generated anomalous signals. The predominant contribution, however, was from the As anomalous signals, which were sufficient to phase the SmPncA structure alone. In Casp6, four cysteines were found to bind cacodyl, a trivalent arsenic group (As (III)), in the presence of the reducing agent, dithiothreitol (DTT), and arsenic atoms were the only anomalous scatterers for SAD phasing. Analyses and discussion of these two As-SAD phasing examples and comparison of As with other traditional heavy atoms that generate anomalous signals, together with a few arsenic-based de novo phasing cases reported previously strongly suggest that As is an ideal anomalous scatterer for SAD phasing in protein crystallography.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000294686100025&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Multidisciplinary SciencesSCI(E)PubMed6ARTICLE9e24227
Shoji Fukushima - One of the best experts on this subject based on the ideXlab platform.
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cancer induction by an organic arsenic compound dimethylarsinic Acid Cacodylic Acid in f344 ducrj rats after pretreatment with five carcinogens
Cancer Research, 1995Co-Authors: Shinji Yamamoto, Yoshitsugu Konishi, Takashi Murai, Tsutomu Matsuda, Isao Matsuiyuasa, Shuzo Otani, Koichi Kuroda, Ginji Endo, Masaaki Shibata, Shoji FukushimaAbstract:Arsenic (As) is environmentally ubiquitous and an epidemiologically significant chemical related to certain human cancers. Dimethylarsinic Acid (Cacodylic Acid; DMA) is one of the major methylated metabolites of ingested arsenicals in most mammals. To evaluate the effects of DMA on chemical carcinogenesis, we conducted a multiorgan bioassay in rats given various doses of DMA. One-hundred twenty-four male F344/DuCrj rats were divided randomly into 7 groups (20 rats each for groups 1-5; 12 rats each for groups 6 and 7). To initiate multiple organs and tissues, animals in groups 1-5 were treated sequentially with diethylnitrosamine (100 mg/kg body weight, i.p., single dose at the commencement) and N-methyl-N-nitrosourea (20 mg/kg body weight, i.p., 4 times, on days 5, 8, 11, and 14). Thereafter, rats received 1,2-dimethylhydrazine (40 mg/kg body weight, s.c., 4 times, on days 18, 22, 26, and 30). During the same period, the animals were sequentially administered N-butyl-N-(4-hydroxybutyl)nitrosamine (0.05% in the drinking water, during weeks 1 and 2) and N-bis(2-hydroxypropyl)nitrosamine (0.1% in the drinking water, during weeks 3 and 4; DMBDD treatment). After a 2-week interval, groups 2-5 were given 50, 100, 200, or 400 ppm DMA, respectively, in the drinking water. Groups 6 and 7, which were not given DMBDD treatment, received 100 and 400 ppm DMA during weeks 6-30. All rats were killed at the end of week 30. In the initiated groups (groups 1-5), DMA significantly enhanced the tumor induction in the urinary bladder, kidney, liver, and thyroid gland, with respective incidences in group 5 (400 ppm DMA) being 80, 65, 65, and 45%. Induction of preneoplastic lesions (glutathione S-transferase placental form-positive foci in the liver and atypical tubules in the kidney) was also significantly increased in DMA-treated groups. Ornithine decarboxylase activity in the kidneys of rats treated with 100 ppm DMA was significantly increased compared with control values (P < 0.001). In conclusion, DMA is acting as a promoter of urinary bladder, kidney, liver, and thyroid gland carcinogenesis in rats, and we speculate that this may be related to cancer induction by As in humans.
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enhancing effects of an organic arsenic compound dimethylarsinic Acid Cacodylic Acid in a multi organ carcinogenesis bioassay
Applied Organometallic Chemistry, 1994Co-Authors: Shinji Yamamoto, Yoshitsugu Konishi, Takashi Murai, Tsutomu Matsuda, Koichi Kuroda, Ginji Endo, Masaaki Shibata, Shoji FukushimaAbstract:The modifying effects of dimethylarsinic Acid (DMA) on tumor induction in various organs were examined using a multi-organ rat carcinogenesis bioassay. A total of 124 six-week-old male F344/DuCrj rats were divided randomly into seven groups. For establishment of wide-spectrum initiation, animals in Groups 1–5 were treated with five carcinogens, namely N-nitrosodiethylamine (DEN), N-methyl-N-nitrosourea (MNU), 1,2-dimethylhydrazine (DMH), N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN) and N-bis(2-hydroxypropyl)nitrosamine (DHPN) in the first four weeks. After a two-week interval, Groups 1–5 were then given 0, 50, 100, 200 and 400 ppm DMA, respectively, in drinking water. Groups 6 and 7 received 100 and 400 ppm DMA without any carcinogen pretreatment. All rats were sacrificed at the end of week 30. In the initiated groups (Groups 1–5), DMA enhanced tumor development in the urinary bladder, kidney, liver and thyroid gland. The main arsenic species in urine samples was DMA itself. In conclusion, the observed enhancement of carcinogenesis in the urinary tract as well as in the liver and thyroid gland may be directly due to this arsenic compound.
Xiang Liu - One of the best experts on this subject based on the ideXlab platform.
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A putative three-stage cysteine modification mechanism for SmPncA.
2013Co-Authors: Xiang Liu, Heng Zhang, Xiao-jun WangAbstract:In stage 1, proton abstraction by Asp9 would increase the nucleophilicities of Cys136 and facilitate nucleophilic attack at Cacodylic Acid (CAD); Proton donation from Asp9 to the hydroxyl group of the CAD would promote As-O bond cleavage and release of H2O as the intermediate in stage 2 collapses to give a dimethylarsinoyl fixed Cys136 in stage 3.
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Anomalous difference Fourier map calculated with final phases at 5 σ.
2013Co-Authors: Xiang Liu, Heng Zhang, Xiao-jun WangAbstract:A. Atoms are shown as sticks model, and colored as follows: carbon, green; oxygen, red; nitrogen, blue; zinc, grey; arsenic, purple. B. The Casp6 structure is shown as a backbone representation. The cysteines modified by Cacodylic Acid are presented in the model.
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Get phases from arsenic anomalous scattering: de novo SAD phasing of two protein structures crystallized in cacodylate buffer.
PloS one, 2011Co-Authors: Xiang Liu, Heng Zhang, Xiao-jun WangAbstract:The crystal structures of two proteins, a putative pyrazinamidase/nicotinamidase from the dental pathogen Streptococcus mutans (SmPncA) and the human caspase-6 (Casp6), were solved by de novo arsenic single-wavelength anomalous diffraction (As-SAD) phasing method. Arsenic (As), an uncommonly used element in SAD phasing, was covalently introduced into proteins by Cacodylic Acid, the buffering agent in the crystallization reservoirs. In SmPncA, the only cysteine was bound to dimethylarsinoyl, which is a pentavalent arsenic group (As (V)). This arsenic atom and a protein-bound zinc atom both generated anomalous signals. The predominant contribution, however, was from the As anomalous signals, which were sufficient to phase the SmPncA structure alone. In Casp6, four cysteines were found to bind cacodyl, a trivalent arsenic group (As (III)), in the presence of the reducing agent, dithiothreitol (DTT), and arsenic atoms were the only anomalous scatterers for SAD phasing. Analyses and discussion of these two As-SAD phasing examples and comparison of As with other traditional heavy atoms that generate anomalous signals, together with a few arsenic-based de novo phasing cases reported previously strongly suggest that As is an ideal anomalous scatterer for SAD phasing in protein crystallography.
