3,294 research outputs found
Reactions of Diazo Carbonyls with [PtX(CH3) (chiral diphosphine)] (X = Cl, Br, I): Chemoselectivity and Diastereoselectivity of Pt-C and Pt-X Carbene Insertion
No full textIn polar solvents (e.g. MeCN), ethyl diazoacetate reacts with [PtXMe(S,S-diop)], where X = Cl, Br, I, to give the corresponding [PtX(CHMeCO2Et)(S,S-diop)] as a 2:1 mixture of diastereoisomers in high yields. The major diastereoisomer of [PtCl(CHMeCO2Et)(S,S-diop)] is readily separated in crystalline form, and its crystal structure reveals that the configuration at the α-carbon is R; it is configurationally stable in CDCl3 for at least 14 days. The factors that influence the diastereoselectivity have been examined by comparing (by 31P NMR spectroscopy) the ratio of diastereoisomers formed in the reactions between [PtXMe(diphos*)] and N2CHCOR: X = Cl, Br, I; diphos* = S,S-diop, R,R-diop, S,S-skewphos, S,S-chiraphos; R = OEt, O(l-menthyl), Ph. In MeCN, the diastereoselectivity is independent of halogen but is a sensitive function of the chiral diphosphine and diazo carbonyl, though no systematic correlations have been divined. In solvents of lower polarity (e.g. CH2Cl2), diazo carbonyls react with [PtXMe(diphos*)] to give the products derived from Pt-X insertion as well as Pt-C insertion. When C6H6 is used as the solvent, the compounds [PtMe(CHICOR)(S,S-diop)], where R = OEt, O(l-menthyl), Ph, are formed in high yields and have been isolated. Redissolving these compounds in MeCN did not lead to isomerization to the Pt-C insertion species [PtI(CHMeCOR)(S,S-diop)]. Several trends have been found relating the extent of Pt-C insertion to the nature of the solvent and the structure of the reagents: the proportion of Pt-C insertion increases with (i) increasing polarity of the solvent (C6H6< CHCl3< CH2-Cl2< (CH3)2SO), (ii) increasing nucleofugacity of the halogen (I < Br < Cl), (iii) decreasing bite angle of the diphosphine (diop < chiraphos, skewphos), and (iv) diazo ketone < diazo ester. A mechanism which is consistent with these observations is discussed. Many of the compounds discussed here have been observed in solution only by 31P NMR, but representative species have been isolated and fully characterized by a combination of elemental analysis, IR spectroscopy, and 1H, 13C, 31P, and 195Pt NMR spectroscopy. © 1995, American Chemical Society. All rights reserved
Trimethylsilyldiazomethane as a diazomethane equivalent in the synthesis of (alpha-halomethyl)platinum(II) complexes
No full textThe reaction between [PtX(2)L(2)] (X = Cl, Br, I; L(2) = 1,5-cyclo-octadiene (cod), 2PPh(3), 2PMePh(2), Ph(2)PCH(2)CH(2)PPh(2), S,S-Ph(2)PCHMeCH(2)CHMePPh(2) (S,S-skewphos)) and an excess of Me(3)SiCHN(2) in a CH2Cl2/Me(2)CO/H2O solvent mixture gives the complexes [Pt(CH(2)X)(2)L(2)]. When [PtX(2)(cod)] is treated with Me(3)SiCHN(2) in a CH2Cl2/Me(2)CO/D2O solvent mixture, the complexes [Pt(CHDX)(2)(cod)] are formed exclusively. The mechanism of these reactions is discussed.</p
Anchimeric assistance by platinum(II) in the epimerizations of [PtX(CHXSiMe(3))(R,R-chiraphos)]
No full textThe crystal structures of solvates of [PtCl(S-CHClSiMe3)(R,R-chiraphos)], [PtBr(S-CHBrSiMe3)(S,S-chiraphos)], and [PtCl(R-CHClSiMe3)(R,R-chiraphos)] (chiraphos = 2,3-bis(diphenylphosphino)butane) have been determined allowing assignment of the absolute stereochemistry for all the species [PtX(CHXSiMe3)(chiraphos)], 1a-c and 2a-c (X = Cl, Br, I). Inversion at the α-carbon in [PtX(CHXSiMe3)(chiraphos)] has been observed at ambient temperature and below for X = Br or I and at elevated temperatures for X = Cl. The rates of these epimerizations have been monitored by 31P NMR spectroscopy (X = Cl or Br) or polarimetry (X = Br or I). All the epimerizations follow first order kinetics and the rate constants kobs have been calculated. From these values the following can be deduced: (i) The rates increase in the order Cl < Br < I. (ii) Addition of large amounts of halide salts has only a small effect on the rate of epimerization. (iii) The reactions are significantly slower in MeCN than in CHCl3 or CH2Cl2. A mechanism consistent with these observations is proposed involving α-halogen migration to the platinum(II)
Paralog of the formylglycine-generating enzyme - retention in the endoplasmic reticulum by canonical and noncanonical signals
No full textGande SL, Mariappan M, Schmidt B, Pringle TH, von Figura K, Dierks T. Paralog of the formylglycine-generating enzyme - retention in the endoplasmic reticulum by canonical and noncanonical signals. FEBS JOURNAL. 2008;275(6):1118-1130.Formylglycine-generating enzyme (FGE) catalyzes in newly synthesized sulfatases the oxidation of a specific cysteine residue to formylglycine, which is the catalytic residue required for sulfate ester hydrolysis. This post-translational modification occurs in the endoplasmic reticulum (ER), and is an essential step in the biogenesis of this enzyme family. A paralog of FGE (pFGE) also localizes to the ER. It shares many properties with FGE, but lacks formylglycine-generating activity. There is evidence that FGE and pFGE act in concert, possibly by forming complexes with sulfatases and one another. Here we show that human pFGE, but not FGE, is retained in the ER through its C-terminal tetrapeptide PGEL, a noncanonical variant of the classic KDEL ER-retention signal. Surprisingly, PGEL, although having two nonconsensus residues (PG), confers efficient ER retention when fused to a secretory protein. Inducible coexpression of pFGE at different levels in FGE-expressing cells did not significantly influence the kinetics of FGE secretion, suggesting that pFGE is not a retention factor for FGE in vivo. PGEL is accessible at the surface of the pFGE structure. It is found in 21 mammalian species with available pFGE sequences. Other species carry either canonical signals (eight mammals and 26 nonmammals) or different noncanonical variants (six mammals and six nonmammals). Among the latter, SGEL was tested and found to also confer ER retention. Although evolutionarily conserved for mammalian pFGE, the PGEL signal is found only in one further human protein entering the ER. Its consequences for KDEL receptor-mediated ER retrieval and benefit for pFGE functionality remain to be fully resolved
Author, publisher and bookseller : a tripartite synergy in Nigerian book industry
No full textThis work is about the roles of Author, Publisher and Bookseller in Book development in
Nigeria. The paper started by delving into the history of Book Publishing in Nigeria after
which it proceeded by defining who an author, a publisher, and a bookseller is and
expatiated on the indispensable roles of these key actors in Nigerian Book Industry and in
the emerging Information Society. Furthermore, the various constraints to book
development were identified while the paper advised on how the Book Industry can be
further promoted in Nigeria. However, the paper concluded and made recommendations
on how the Book sector can help in enhancing scholarship in the country
Author's reply: Comments on delay-dependent robust H-infinity control for uncertain systems with a state-delay
No full textIn the above-mentioned comment, the authors point out a technical problem with the paper [Lee, Y. S., Moon, Y. S., Kwon, W. H., & Park, P. G. (2004). Delay-dependent robust H-infinity control for uncertain systems with a state-delay. Automatica, 40(1), 65-72]. We show this technical problem can be solved by changing the proof of Theorem 3.1. (C) 2007 Elsevier Ltd. All rights reserved.X115sciescopu
Extramedullary plasmacytoma in a horse with ptyalism and dysphagia
No full textA Clydesdale mare was examined for weight loss, inappetence, ptyalism, and dysphagia. The main abnormality revealed by serum biochemistry was a marked hyperglobulinemia, and protein electrophoresis revealed a monoclonal gammopathy in the gamma region. The urine was positive for Bence Jones proteins. These findings suggested a plasma cell tumor. The neoplasm could not be located with extensive antemortem examination. At postmortem, neoplastic cells morphologically compatible with plasma cells and positive for equine IgG with imunoperoxidase staining infiltrated the pericardium, mediastinal stromal tissues, adrenal glands, meninges, atrioventricular valves, aorta, abdominal and thoracic fat, and nerves, including the trigeminal nerve. The neoplastic cells invading the cranial nerves were responsible for many of the presenting signs.PT: J; CR: BARLOGIE B, 1995, WILLIAMS HEMATOLOGY, P1109 BAUER JD, 1974, CLIN LAB METHODS, P15 BRAUND KG, 1978, J AM VET MED ASSOC, V172, P1407 BRAUND KG, 1979, J AM VET MED ASSOC, V174, P1321 CALNEK BW, 1991, DIS POULTRY, P342 DIMOPOULOS MA, 1994, BLOOD, V83, P1452 DREW RA, 1974, EQUINE VET J, V3, P131 DUNCAN JR, 1994, VET LAB MED CLIN PAT, P112 DUNCAN JR, 1994, VET LAB MED CLIN PAT, P63 EDWARDS DF, 1993, J VET INTERN MED, V7, P169 HENRY M, 1994, J AM VET MED ASSOC, V194, P392 JACKSON MW, 1994, J AM VET MED ASSOC, V204, P404 KENT JE, 1990, EQUINE VET J, V22, P373 MANDEL NS, 1994, J AM ANIM HOSP ASSOC, V30, P603 TRAUBDARGATZ J, 1985, EQUINE VET J, V17, P373; NR: 15; TC: 9; J9: J VET DIAGN INVEST; PG: 3; GA: 312MPSource type: Electronic(1
An Econometric model for the evolution of the Romanian Interbank Bid Rate (ROBID) in the context of the international financial crisis
No full textThe paper presents the econometric modeling of overnight inter-banking interest rates (ROBID) in our country, the analyzed period is between 1999-2010. The international financial crises had a great impact on the level of inter-banking interest rates after 2007 and it reflects the new level of risk for the Romanian system banking. The econometric model used in modeling the interest rates is an autoregressive moving average (ARMA) model, the ARMA model is typically applied to time series data; the paper propose several ARMA models, applies econometric tests and based on them the analyzed series (the inter-banking interest rates) forecast will be made.ROBID, ARIMA model, financial crisis, forecast.
Identifying which septic patients have increased mortality risk using severity scores: a cohort study
No full textBackground: Early aggressive therapy can reduce the mortality associated with severe sepsis but this relies on prompt recognition, which is hindered by variation among published severity criteria. Our aim was to test the performance of different severity scores in predicting mortality among a cohort of hospital inpatients with sepsis. Methods: We anonymously linked routine outcome data to a cohort of prospectively identified adult hospital inpatients with sepsis, and used logistic regression to identify associations between mortality and demographic variables, clinical factors including blood culture results, and six sets of severity criteria. We calculated performance characteristics, including area under receiver operating characteristic curves (AUROC), of each set of severity criteria in predicting mortality. Results: Overall mortality was 19.4% (124/640) at 30 days after sepsis onset. In adjusted analysis, older age (odds ratio 5.79 (95% CI 2.87-11.70) for ≥80y versus <60y), having been admitted as an emergency (OR 3.91 (1.31-11.70) versus electively), and longer inpatient stay prior to sepsis onset (OR 2.90 (1.41-5.94) for >21d versus <4d), were associated with increased 30 day mortality. Being in a surgical or orthopaedic, versus medical, ward was associated with lower mortality (OR 0.47 (0.27-0.81) and 0.26 (0.11-0.63), respectively). Blood culture results (positive vs. negative) were not significantly association with mortality. All severity scores predicted mortality but performance varied. The CURB65 community-acquired pneumonia severity score had the best performance characteristics (sensitivity 81%, specificity 52%, positive predictive value 29%, negative predictive value 92%, for 30 day mortality), including having the largest AUROC curve (0.72, 95% CI 0.67-0.77). Conclusions: The CURB65 pneumonia severity score outperformed five other severity scores in predicting risk of death among a cohort of hospital inpatients with sepsis. The utility of the CURB65 score for risk-stratifying patients with sepsis in clinical practice will depend on replicating these findings in a validation cohort including patients with sepsis on admission to hospital
Parameters of the experiment.
No full text<p>N: animal number; IN: postoperative identification number; G: group of animals; S: sex; PM: type of Pringle maneuver; IPM: intermittent Pringle maneuver; pC: pre-conditioning; DoE: date of euthanasia; C: colitis; CG: grade of colonic inflammation; P: peritonitis; PG: grade of peritoneal irritation,</p><p>* no footnotes are needed for this symbol.</p><p>Parameters of the experiment.</p
- …
