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https://www.readbyqxmd.com/read/26907463/a-br%C3%A3-nsted-acid-amino-acid-as-a-synergistic-catalyst-for-asymmetric-list-lerner-barbas-aldol-reactions
#1
Dhevalapally B Ramachary, Kodambahalli S Shruthi
Herein, for the first time, a combination of L-amino acid, (R)-5,5-dimethyl thiazolidinium-4-carboxylate (L-DMTC) with simple Brønsted acid TFA is reported as the suitable synergistic catalyst for the List-Lerner-Barbas aldol (LLB-A) reaction of less reactive 2-azidobenzaldehydes with various ketones at ambient temperature to furnish the optically active functionalized (2-azidophenyl)alcohols with very good yields, dr's, and ee's. This method gives first time access to the novel azido-containing multifunctional compounds, which are applicable in material to medicinal chemistry...
March 18, 2016: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/26776541/efficient-methods-for-implementation-of-multi-level-nonrigid-mass-preserving-image-registration-on-gpus-and-multi-threaded-cpus
#2
Nathan D Ellingwood, Youbing Yin, Matthew Smith, Ching-Long Lin
BACKGROUND AND OBJECTIVE: Faster and more accurate methods for registration of images are important for research involved in conducting population-based studies that utilize medical imaging, as well as improvements for use in clinical applications. We present a novel computation- and memory-efficient multi-level method on graphics processing units (GPU) for performing registration of two computed tomography (CT) volumetric lung images. METHODS: We developed a computation- and memory-efficient Diffeomorphic Multi-level B-Spline Transform Composite (DMTC) method to implement nonrigid mass-preserving registration of two CT lung images on GPU...
April 2016: Computer Methods and Programs in Biomedicine
https://www.readbyqxmd.com/read/26353206/convex-discriminative-multitask-clustering
#3
Xiao-Lei Zhang
Multitask clustering tries to improve the clustering performance of multiple tasks simultaneously by taking their relationship into account. Most existing multitask clustering algorithms fall into the type of generative clustering, and none are formulated as convex optimization problems. In this paper, we propose two convex Discriminative Multitask Clustering (DMTC) objectives to address the problems. The first one aims to learn a shared feature representation, which can be seen as a technical combination of the convex multitask feature learning and the convex Multiclass Maximum Margin Clustering (M3C)...
January 2015: IEEE Transactions on Pattern Analysis and Machine Intelligence
https://www.readbyqxmd.com/read/22892842/validation-of-polo-like-kinase-1-as-a-therapeutic-target-in-pancreatic-cancer-cells
#4
Chao Zhang, Xiaodong Sun, Yuan Ren, Yunbo Lou, Jun Zhou, Min Liu, Dengwen Li
Polo-like kinase 1 (PLK1) is a serine/threonine protein kinase and plays a critical role in mitosis. PLK1 has also been regarded as a valuable target for cancer treatment, and several PLK1 inhibitors are currently undergoing clinical investigations. In this study, our data show that the expression level of PLK1 is upregulated in human pancreatic cancer cells. Molecular modeling studies indicate that DMTC inhibits PLK1 activity through competitive displacement of ATP from its binding pocket. Our data further show that DMTC suppresses the proliferation of pancreatic cancer cells and induces the formation of multinucleated cells, ultimately resulting in apoptosis...
October 2012: Cancer Biology & Therapy
https://www.readbyqxmd.com/read/18486571/development-of-an-analytical-method-to-confirm-toxic-trimethylated-tin-in-human-urine
#5
Yoshihiro Suzuki, Yoko Endo, Masanori Ogawa, Yangho Kim, Nobuhiko Onda, Kenzo Yamanaka
Dimethyltin dichloride (DMTC) is widely used as a heat stabilizer in manufacturing the polyvinyl chloride. We previously reported a case of acute DMTC poisoning with neurological manifestations very similar to trimethylated tin (TMT) encephalopathy, based on results of speciation analysis of methylated tins in the patient's urine with use of a combination of high performance liquid chromatography and inductively coupled plasma-mass spectrometry (HPLC-ICP-MS), which yielded peaks corresponding to DMT and TMT...
June 1, 2008: Journal of Chromatography. B, Analytical Technologies in the Biomedical and Life Sciences
https://www.readbyqxmd.com/read/18310024/biosynthesis-of-elloramycin-in-streptomyces-olivaceus-requires-glycosylation-by-enzymes-encoded-outside-the-aglycon-cluster
#6
Angelina Ramos, Felipe Lombó, Alfredo F Braña, Jürgen Rohr, Carmen Méndez, José A Salas
Elloramycin is an anthracycline-like antitumour drug produced by Streptomyces olivaceus Tü2353. Cosmid cos16F4 has been previously shown to direct the biosynthesis of the elloramycin aglycon 8-demethyltetracenomycin C (8-DMTC), but not elloramycin. Sequencing of the 24.2 kb insert in cos16F4 shows the presence of 17 genes involved in elloramycin biosynthesis (elm genes) together with another additional eight ORFs probably not involved in elloramycin biosynthesis. The 17 genes would code for the biosynthesis of the polyketide moiety, sugar transfer, methylation of the tetracyclic ring and the sugar moiety, and export...
March 2008: Microbiology
https://www.readbyqxmd.com/read/18253893/an-organotin-mixture-found-in-polyvinyl-chloride-pvc-pipe-is-not-immunotoxic-to-adult-sprague-dawley-rats
#7
Jamie C DeWitt, Carey B Copeland, Robert W Luebke
Organotin compounds used in polyvinyl chloride (PVC) pipe production are of concern to the U.S. Environmental Protection Agency (EPA) because they leach from supply pipes into drinking water and are reported multisystem toxicants. Immune function was assessed in male Sprague-Dawley rats exposed to the mixture of organotins used in PVC pipe production. Although several of these organotins are reported immunotoxicants, their immunotoxicity as a mixture when given by drinking water has not been evaluated. Adult male rats were given drinking water for 28 d containing a mixture of dibutyltin dichloride (DBTC), dimethyltin dichloride (DMTC), monobutyltin trichloride (MBT), and monomethyltin trichloride (MMT) in a 2:2:1:1 ratio, respectively, at 3 different concentrations (5:5:2...
2008: Journal of Toxicology and Environmental Health. Part A
https://www.readbyqxmd.com/read/18163545/methylation-of-dimethyltin-in-mice-and-rats
#8
Koichi Furuhashi, Masanori Ogawa, Yoshihiro Suzuki, Yoko Endo, Yangho Kim, Gaku Ichihara
Organotins are widely used as stabilizers of polyvinyl chloride and as catalysts or biocides. It is well known that dimethyltin (DMT) is less neurotoxic than trimethyltin (TMT). A Korean worker who was exposed to DMT compounds showed neurological symptoms similar to those of TMT encephalopathy, in association with high levels of both DMT and TMT in the urine and blood. The case suggested the possibility of the methylation of DMT in humans. Here, we investigated whether TMT is detected in the urine of mice and rats exposed only to DMT dichloride (DMTC)...
February 2008: Chemical Research in Toxicology
https://www.readbyqxmd.com/read/17321662/immune-function-is-not-impaired-in-sprague-dawley-rats-exposed-to-dimethyltin-dichloride-dmtc-during-development-or-adulthood
#9
Jamie C DeWitt, Carey B Copeland, Robert W Luebke
Organotins are used commercially as pesticides, antifouling agents and stabilizers for polyvinyl chloride (PVC) pipe. Mono- and di-substituted butyltins, used in PVC pipe production, are of concern to the US EPA because they leach from supply pipes into drinking water and are reported multisystem toxicants. We assessed several immune functions in Sprague-Dawley rats after adult or developmental dimethyltin dichloride (DMTC) exposure because various organotins have been reported to be immunotoxic. Adult male and female rats were given drinking water containing 0, 20 or 40 mg DMTC/L (0, 1...
April 11, 2007: Toxicology
https://www.readbyqxmd.com/read/16828843/adsorption-of-acid-red-73-on-copper-dithiocarbamate-precipitate-type-solid-wastes
#10
Fenglian Fu, Ya Xiong, Baoping Xie, Runming Chen
Three solid wastes, copper N,N'-bis(dithiocarboxy)piperazine ([CuBDP](n)), copper diethyldithiocarbamate (Cu(DDTC)(2)) and copper dimethyldithiocarbamate (Cu(DMTC)(2)), were prepared and tested as adsorbents to remove Acid Red 73 from wastewater. It was found that the three precipitates all could effectively adsorb the dye but their adsorption abilities were rather different. The maximum adsorption amounts of the coordination polymer precipitate [CuBDP](n) reached as high as 364mg g(-1), much greater than those of Cu(DDTC)(2) and Cu(DMTC)(2) (42...
January 2007: Chemosphere
https://www.readbyqxmd.com/read/16359687/optimizing-the-integrated-pulsed-amperometric-multicycle-step-waveform-for-the-determination-of-tetracyclines
#11
COMPARATIVE STUDY
Yu-e Cai, Yaqi Cai, Yali Shi, Shifen Mou, Yiqiang Lu
A method of modified integrated pulsed amperometric detection with multicycle step waveform (Multi-IPAD) following high-performance liquid chromatography (HPLC) was applied for the determination of tetracyclines (TCs) including dimethyltetracycline (DMTC), oxytetracycline (OTC) and tetracycline (TC). The key advantages of the Multi-IPAD are the abilities to enhance sensitivity and reproducibility and the ability to keep working electrode clean through the use of a high-frequent waveform alteration in integration step and the use of a cleaning potential, which is quite different from conventional three-step potential waveform...
June 16, 2006: Journal of Chromatography. A
https://www.readbyqxmd.com/read/14653666/dimethylthiocarbamate-dmtc-an-alcohol-protecting-group
#12
D K Barma, A Bandyopadhyay, Jorge H Capdevila, J R Falck
Dimethylthiocarbamates (DMTCs), prepared from the corresponding alcohols using commercial dimethylthiocarbamoyl chloride, are spectrally simple, achiral, and nonpolar. DMTCs are moderately to highly stable to a wide range of reagents and conditions including metal hydrides, hydroboration, ylides, NaOH, HCl, organolithiums, Grignards, DDQ, PCC, Swern, n-Bu(4)NF, CrCl(2), heat, and Lewis acids. They are readily removed by NaIO(4) or H(2)O(2) in the presence of other common alcohol protecting groups. [structure: see text]...
December 11, 2003: Organic Letters
https://www.readbyqxmd.com/read/14599584/interactions-of-tetracycline-and-its-derivatives-with-dna-in-vitro-in-presence-of-metal-ions
#13
Mateen A Khan, Javed Musarrat
The interactions of calf thymus DNA with tetracycline (TC), 7-chlorotetracycline (CTC) and 6-dimethyl-7-chlorotetracycline (DMTC) were assessed employing spectrofluorometric and circular dichroism (CD) techniques. The Scatchard analysis revealed relatively lesser binding affinity of TC (Ka= 1.2 x 10(7) lmol(-1)) vis-a-vis CTC (Ka= 3.4 x 10(7) lmol(-1)) and DMTC (Ka= 3.0 x 10(7) lmol(-1)) with DNA. The data suggested both the intercalative and electrostatic nature of binding between the tetracyclines and DNA...
November 2003: International Journal of Biological Macromolecules
https://www.readbyqxmd.com/read/12650911/mechanism-of-dna-strand-breakage-induced-by-photosensitized-tetracycline-cu-ii-complex
#14
Mateen A Khan, Jamal Mustafa, Javed Musarrat
Tetracyclines (TCs) in combination with Cu(II) ions exhibited significant DNA damaging potential vis a vis tetracyclines per se. Interaction of tetracyclines with DNA resulted in alkylation at N-7 and N-3 positions of adenine and guanine bases, and caused destabilization of DNA secondary structure. Significant release of acid-soluble nucleotides from tetracycline-modified DNA upon incubation with S(1) nuclease ascertained the formation of single stranded regions in the DNA. Also, the treatment of tetracycline-modified DNA with 0...
April 9, 2003: Mutation Research
https://www.readbyqxmd.com/read/11666388/chemical-and-biological-studies-of-dichloro-2-dimethylamino-methyl-phenyl-gold-iii
#15
Richard V. Parish, Brian P. Howe, Jonathan P. Wright, Jürgen Mack, Robin G. Pritchard, Robert G. Buckley, Amanda M. Elsome, Simon P. Fricker
Several new organogold(III) derivatives of the type [AuX(2)(damp)] (damp = o-C(6)H(4)CH(2)NMe(2)) have been prepared [X = CN, SCN, dtc, or X(2) = tm; dtc = R(2)NCS(2) (R = Me (dmtc) or Et (detc)); tm = SCH(CO(2))CH(2)CO(2)Na] together with [AuCl(tpca)(damp)]Cl (tpca = o-Ph(2)PC(6)H(4)CO(2)H), [Au(dtc)(damp)]Y (Y = Cl, BPh(4)) and K[Au(CN)(3)(damp)]. The (13)C NMR spectra of these and previous derivatives have been fully assigned. In [Au(dtc)(2)(damp)] and K[Au(CN)(3)(damp)], the damp ligand is coordinated only through carbon, as shown by X-ray crystallography and/or NMR...
March 13, 1996: Inorganic Chemistry
https://www.readbyqxmd.com/read/11457388/amino-acid-catalyzed-direct-asymmetric-aldol-reactions-a-bioorganic-approach-to-catalytic-asymmetric-carbon-carbon-bond-forming-reactions
#16
K Sakthivel, W Notz, T Bui, C F Barbas
Direct asymmetric catalytic aldol reactions have been successfully performed using aldehydes and unmodified ketones together with commercially available chiral cyclic secondary amines as catalysts. Structure-based catalyst screening identified L-proline and 5,5-dimethyl thiazolidinium-4-carboxylate (DMTC) as the most powerful amino acid catalysts for the reaction of both acyclic and cyclic ketones as aldol donors with aromatic and aliphatic aldehydes to afford the corresponding aldol products with high regio-, diastereo-, and enantioselectivities...
June 6, 2001: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/11306350/identification-of-a-sugar-flexible-glycosyltransferase-from-streptomyces-olivaceus-the-producer-of-the-antitumor-polyketide-elloramycin
#17
G Blanco, E P Patallo, A F Braña, A Trefzer, A Bechthold, J Rohr, C Méndez, J A Salas
BACKGROUND: Elloramycin is an anthracycline-like antitumor drug related to tetracenomycin C which is produced by Streptomyces olivaceus Tü2353. Structurally is a tetracyclic aromatic polyketide derived from the condensation of 10 acetate units. Its chromophoric aglycon is glycosylated with a permethylated L-rhamnose moiety at the C-8 hydroxy group. Only limited information is available about the genes involved in the biosynthesis of elloramycin. From a library of chromosomal DNA from S...
March 2001: Chemistry & Biology
https://www.readbyqxmd.com/read/11266551/dna-methyltransferases-of-the-cyanobacterium-anabaena-pcc-7120
#18
A V Matveyev, K T Young, A Meng, J Elhai
From the characterization of enzyme activities and the analysis of genomic sequences, the complement of DNA methyltransferases (MTases) possessed by the cyanobacterium ANABAENA PCC 7120 has been deduced. ANABAENA has nine DNA MTases. Four are associated with Type II restriction enzymes (AVAI, AVAII, AVAIII and the newly recognized inactive AVAIV), and five are not. Of the latter, four may be classified as solitary MTases, those whose function lies outside of a restriction/modification system. The group is defined here based on biochemical and genetic characteristics...
April 1, 2001: Nucleic Acids Research
https://www.readbyqxmd.com/read/6933893/toxicity-of-organotin-compounds-in-chicken-and-rats
#19
M Renhof, U Kretzer, T Schürmeyer, H Skopnik, F H Kemper
Di-methyltin-dichloride (DMTC), di-butyltin-dichloride (DBTC), di-octyltin-dichloride (DOTC) and two commercial products (CP 1, CP 2) used as stabilizers in plastics induce a dose-related decrease of the thymus weight in young rats when given by gastric intubation for 10 or 14 days; in the chicken a decrease of the bursa Fabricii weight can also be observed. It is of interest, that there are distinct differences in response between the animal species. The sensitivity in acute toxicity tests does not correspond with the sensitivity of thymus and bursa Fabricii...
1980: Archives of Toxicology. Supplement., Archiv Für Toxikologie. Supplement
https://www.readbyqxmd.com/read/6611265/hexokinase-isoenzymes-from-anaplastic-and-differentiated-medullary-thyroid-carcinoma-in-the-rat
#20
G Rijksen, R Oskam, C F Molthoff, S J Lee On, M Streefkerk, G E Staal
The activity, isoenzyme distribution and compartmentation of hexokinase (ADP: D-hexose-6-phosphotransferase, EC 2.7.1.1) were compared in slowly growing, well-differentiated medullary thyroid carcinoma (DMTC) and rapidly proliferating anaplastic thyroid carcinoma (AMTC) in the rat. Individual isoenzymes from either soluble or particulate fractions after solubilization were obtained by fast protein liquid chromatography and were kinetically analyzed either in soluble form or after (re)binding to rat liver mitochondria...
July 1984: European Journal of Cancer & Clinical Oncology
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