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Selected AbstractsMultinuclear magnetic resonance study of the structure and tautomerism of azide and iminophosphorane derivatives of chloropyridazinesMAGNETIC RESONANCE IN CHEMISTRY, Issue 8 2002Piotr Cmoch Abstract Some azido- and iminophosphorane derivatives of 3,6-dichloro- and 3,4,5,6-tetrachloropyridazine were synthesized and studied by means of NMR measurements. Based on multinuclear data (chemical shifts, coupling constants) for compounds containing the azide group, no potentially possible tetrazole,azide equilibrium can be observed, even under acidic conditions. An unusual substitution of a chlorine atom (in position 4) of tetrachloropyridazine in the reaction with hydrazine was demonstrated by NMR measurements of two newly synthesized compounds containing azido- and iminophosphorane groups. Using multinuclear magnetic resonance data, the sites of ethylation and protonation of azido- and iminophosphorane derivatives of chloropyridazines were established. In the case of the tetrazolopyridazines, ethylation occurs at the N1, and N2, atoms, whereas for monocyclic compounds it takes place at the N1 and/or N2 atoms of the pyridazine ring. Preferred sites of protonation are the N1, atom of the tetrazole ring and the N1 atom of the pyridazine ring. Moreover, the structures of potassium salts of 6-(3-cyano-1-triazeno)tetrazolo[1,5- b] pyridazine and its amido derivative were established using NMR data, especially 15N NMR chemical shifts. Copyright © 2002 John Wiley & Sons, Ltd. [source] Synthesis, Characterization, and Protonation Reactions of Ar-BIAN and Ar-BICAT Diimine Platinum Diphenyl ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 9 2010Jerome Parmene Abstract PtII diphenyl complexes (N,N)PtPh2 [N,N = diimines Ar,N=C(An)C=N,Ar with Ar = substituted aryl groups] have been prepared and characterized by 1H, 13C, and 195Pt NMR spectroscopy. The 195Pt NMR spectroscopic data establish the electronic influence exerted by substituents at the backbone of the diimine ligand system to the metal center. When compared to diimines Ar,N=CMe,CMe=N,Ar, the electron-withdrawing ability of the Ar-BIAN ligand and the electron-donating ability of the O,O-heterocyclic Ar-BICAT systems are demonstrated. Trends in 195Pt NMR chemical shifts suggest that electronic tuning of the metal center is better achieved through variations of the diimine backbone substituents rather than variation of the substituents at the N-Aryl groups. Protonation of (N,N)PtPh2 in dichloromethane/acetonitrile at ,78 °C furnishes the corresponding PtIV hydrides (N,N)PtPh2H(NCMe)+. The PtIV hydrides liberate benzene with the formation of (N,N)PtPh(NCMe)+ when the temperature is raised. A second protonation and rapid benzene elimination produces the dicationic PtII species (N,N)Pt(NCMe)22+ at approximately 50 °C. Protonation of (N,N)PtPh2 in the absence of acetonitrile results in the clean formation of (N,N)PtPh(,2 -C6H6)+ at temperatures that depend on the steric hindrance provided by the alkyl substituents at the diimine N-aryl groups. These findings support the notion that the metal is the kinetically preferred site of protonation. The results qualitatively agree with a recent mechanistic study of protonation-induced reactions of (diimine)PtPh2 complexes that bear simple methyl substituents at the diimine backbone. Several compounds have been crystallographically characterized. All complexes have the expected square planar environment at the metal. Modest variations in the metric parameters suggest that the Ar-BICAT system has a weaker trans influence than the Ar-BIAN and Ar-DAB systems. [source] Imputation of 10-year osteoporotic fracture rates from hip fractures: A clinical validation studyJOURNAL OF BONE AND MINERAL RESEARCH, Issue 2 2010William D Leslie Abstract The World Health Organization (WHO) fracture risk assessment system (FRAX) allows for calibration from country-specific fracture data. The objective of this study was to evaluate the method for imputation of osteoporotic fracture rates from hip fractures alone. A total of 38,784 women aged 47.5 years or older at the time of baseline femoral neck bone mineral density (BMD) measurement were identified in a database containing all clinical dual energy X-ray absorptiometry (DXA) results for the Province of Manitoba, Canada. Health service records were assessed for the presence of nontrauma osteoporotic fracture codes after BMD testing (431 hip, 787 forearm, 336 clinical vertebral, and 431 humerus fractures). Ten-year hip and osteoporotic fracture rates were estimated by the Kaplan-Meier method. The population was stratified by age (50 to 90 years, 5-year width strata) and again by femoral neck T -scores (,4.0 to 0.0, 0.5 SD width strata). Within each stratum, the ratio of hip to osteoporotic fractures was calculated and compared with the predicted ratio from FRAX. Increasing age was associated with greater predicted hip-to-osteoporotic ratios (youngest 0.07 versua oldest 0.41) and observed ratios (youngest 0.10 versus oldest 0.48). Lower T -scores were associated with greater predicted (highest 0.04 versus lowest 0.71) and observed ratios (highest 0.06 versus lowest 0.44). There was a strong positive correlation between predicted and observed ratios (Spearman r,=,0.90,0.97, p,<,.001). For 14 of the 18 strata, the predicted ratio was within the observed 95% confidence interval (CI). Since collection of population-based hip fracture data is considerably easier than collection of non,hip fracture data, this study supports the current emphasis on using hip fractures as the preferred site for FRAX model calibration. © 2010 American Society for Bone and Mineral Research [source] Long-Term Mechanical Consequences of Permanent Right Ventricular Pacing: Effect of Pacing SiteJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 10 2010DARRYL P. LEONG M.B.B.S. Optimal Right Ventricular Pacing,Introduction: Long-term right ventricular apical (RVA) pacing has been associated with adverse effects on left ventricular systolic function; however, the comparative effects of right ventricular outflow tract (RVOT) pacing are unknown. Our aim was therefore to examine the long-term effects of septal RVOT versus RVA pacing on left ventricular and atrial structure and function. Methods: Fifty-eight patients who were prospectively randomized to long-term pacing either from the right ventricular apex or RVOT septum were studied echocardiographically. Left ventricular (LV) and atrial (LA) volumes were measured. LV 2D strain and tissue velocity images were analyzed to measure 18-segment time-to-peak longitudinal systolic strain and 12-segment time-to-peak systolic tissue velocity. Intra-LV synchrony was assessed by their respective standard deviations. Interventricular mechanical delay was measured as the difference in time-to-onset of systolic flow in the RVOT and LV outflow tract. Septal A' was measured using tissue velocity images. Results: Following 29 ± 10 months pacing, there was a significant difference in LV ejection fraction (P < 0.001), LV end-systolic volume (P = 0.007), and LA volume (P = 0.02) favoring the RVOT-paced group over the RVA-paced patients. RVA-pacing was associated with greater interventricular mechanical dyssynchrony and intra-LV dyssynchrony than RVOT-pacing. Septal A' was adversely affected by intra-LV dyssynchrony (P < 0.05). Conclusions: Long-term RVOT-pacing was associated with superior indices of LV structure and function compared with RVA-pacing, and was associated with less adverse LA remodeling. If pacing cannot be avoided, the RVOT septum may be the preferred site for right ventricular pacing. (J Cardiovasc Electrophysiol, Vol. 21, pp. 1120-1126) [source] Electronic structure and reactivity of guanylthiourea: A quantum chemical studyJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 6 2010Ahmed Mehdi Abstract Electronic structure analysis of guanylthiourea (GTU) and its isomers has been carried out using quantum chemical methods. Two major tautomeric classes (thione and thiol) have been identified on the potential energy (PE) surface. In both the cases conjugation of pi-electrons and intramolecular H-bonds have been found to play a stabilizing role. Various isomers of GTU on its PE surface have been analyzed in two different groups (thione and thiol). The interconversion from the most stable thione conformer (GTU-1) to the most stable thiol conformer (GTU-t1) was found to take place via bimolecular process which involves protonation at sulfur atom of GTU-1 followed by subsequent CN bond rotation and deprotonation. The detailed analysis of the protonation has been carried out in gas phase and aqueous phase (using CPMC model). Sulfur atom (S1) was found to be the preferred protonation site (over N4) in GTU-1 in gas phase whereas N4 was found to be the preferred site of protonation in aqueous medium. The mechanism of S-alkylation reaction in GTU has also been studied. The formation of alkylated analogs of thiol isomers (alkylated guanylthiourea) is believed to take place via bimolecular process which involves alkyl cation attack at S atom followed by CN bond rotation and deprotonation. The reactive intermediate RS(NH2)CNC(NH2)2+ belongs to the newly identified ,N(,L)2 class of species and provides the necessary dynamism for easy conversion of thione to thiol. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010 [source] Synthesis, characterization and in vivo activity of salmon calcitonin coconjugated with lipid and polyethylene glycolJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 4 2009Weiqiang Cheng Abstract An irreversible lipidized salmon calcitonin (sCT) analog, Mal-sCT, was previously shown to have comparable hypocalcemic activity to sCT in vivo. This study reports on the synthesis, characterization and pharmacological activity of novel PEGylated Mal-sCT analogs. Mal-sCT, prepared by conjugating sCT via thio-ether bonds with aqueous-soluble palmitic acid derivative at Cys 1 and Cys 7, was reacted with mPEG-succinimide (mPEG-Suc, 5 kDa). The products were purified and then identified by MALDI-TOF MS and HPLC. Mal-sCT was conjugated with 1 (1PEG-Mal-sCT) or 2 (2PEG-Mal-sCT) PEG chains at Lys 11 and Lys 18, the former being the preferred site of conjugation at higher mPEG-Suc/Mal-sCT ratio. Circular dichroism analysis showed the PEGylated Mal-sCT analogs to possess a robust helical conformation, while size measurement by dynamic light scattering indicated a propensity of the peptides to self-aggregate in aqueous solutions. Both 1PEG-Mal-sCT and 2PEG-Mal-sCT were more stable in rodent intestinal fluids than sCT or Mal-sCT. However, 1PEG-Mal-sCT had comparable hypocalcemic activity to Mal-sCT when injected subcutaneously in the rat, while 2PEG-Mal-sCT was inactive. 1PEG-Mal-sCT was inactive when administered orally in the rat. This study suggested PEGylation of Mal-sCT increased the stability of the lipidized peptide to enzyme degradation, but did not enhance its hypocalcemic activity. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:1438,1451, 2009 [source] Habitat selection in a recovering Osprey Pandion haliaetus populationIBIS, Issue 3 2001ASKO LOHMUS Sequential habitat occupation and productivity of Ospreys Pandion haliaetus were studied in the recovering Estonian population from 1985 to 1999. During this period, the number of known nests increased from five to 32. Nest-sites closer to the foraging grounds and with more lakes nearby were occupied first and had the highest productivity. Through a reduction in the quality of sites available, the average productivity of Ospreys decreased as their numbers rose, consistent with despotic distribution models. The sites occupied first during the recolonization were also those that had been the last to be abandoned during the population's decline prior to 1980. However, newcomers preferred sites near established pairs. Therefore, conspecific attraction explained some stochasticity left unexplained by deterministic resource models. [source] Tree and forest characteristics influence sleeping site choice by golden lion tamarinsAMERICAN JOURNAL OF PRIMATOLOGY, Issue 9 2007Sarah J. Hankerson Abstract Lion tamarin monkeys are among a small number of primates that repeatedly use a few tree holes for the majority of their sleeping sites. To better understand why lion tamarins rely on tree holes as sleeping sites, we compared the physical characteristics of frequently used sleeping sites, infrequently used sleeping sites, and randomly selected forest locations at multiple spatial scales. From 1990 to 2004, we recorded 5,235 occurrences of sleeping site use by 10 groups of golden lion tamarins (Leontopithecus rosalia) in Poço das Antas Reserve, Rio de Janeiro State, Brazil. Of those, 63.6% were tree holes. Bamboo accounted for an additional 17.5% of observations. Frequently used tree holes were more likely to be found in living trees and their entrances were at lower canopy heights than infrequently used tree holes. We also found that frequently used sleeping sites, in comparison to random sites, were more likely to be found on hillsides, be close to other large trees, have a lower percent of canopy cover, and have larger diameter at breast height. Topography and small-scale variables were more accurate than were habitat-level classifications in predicting frequently used sleeping sites. There are ample tree holes available to these lion tamarins but few preferred sites to which they return repeatedly. The lion tamarins find these preferred sites wherever they occur including in mature forest and in relics of older forest embedded in a matrix of secondary forest. Am. J. Primatol. 69:976,988, 2007. © 2007 Wiley-Liss, Inc. [source] | ||||||||||||||||