The enthalpies of dissociation of the N-O bonds in two quinoxaline derivatives

The present work reports the first experimental thermochemical study of mono-N-oxides derived from quinoxaline, namely, 3-methoxycarbonyl-2-methyl-quinoxaline N-oxide and 3-ethoxycarbonyl-2-methyl-quinoxaline N-oxide. The values of the enthalpies of formation, in the condensed state, and of the enthalpies of sublimation, derived from static bomb calorimetry and Calvet microcalorimetry measurements, respectively, are combined to derive the standard molar enthalpies of formation in the gaseous phase for these two compounds. From the latter values, the first and second N-O bond dissociation enthalpies for the corresponding di-N-oxides have been obtained. The gas-phase experimental results are also compared with calculated data obtained with a density functional theory approach. Copyright (c) 2008 John Wiley & Sons, Ltd

Experimental and computational study of the energetics of hydantoin and 2-thiohydantoin

This work reports an experimental and a theoretical study of two imidazolidine derivatives, hydantoin (CAS No. 461-72-3) and 2-thiohydantoin (CAS No. 503-87-7). The standard (p degrees = 0.1 MPa) molar energies of combustion of hydantoin and 2-thiohydantoin were measured by static and rotating bomb combustion calorimetry, respectively. The standard molar enthalpies of sublimation, at T = 298.15 K, were derived from the temperature dependence of the vapour pressures of these compounds, measured by the Knudsen-effusion technique, and from high temperature Calvet microcalorimetry. The conjugation of these experimental results enables the calculation of the standard molar enthalpies of formation in the gaseous state, at T = 298.15 K, which are discussed in terms of structural contributions. We have also estimated the gas-phase enthalpy of formation from high-level ab initio molecular orbital calculations at the G3MP2B3 level of theory, being the computed values in good agreement with the experimental ones. Furthermore, this composite approach was also used to obtain information about the gas-phase basicities, proton and electron affinities and adiabatic ionization enthalpies

ENERGETIC AND STRUCTURAL EFFECTS ON OXYGEN OR SULFUR HETEROPOLYCYCLIC COMPOUNDS

The present article involves a comparative study of the influence of oxygen or sulfur heteroatoms present in the central ring of polycyclic compounds, in order to clarify the correlation between the respective thermophysical or thermochemical properties and structural characteristics. Considering the importance of these types of compounds for their broad spectrum of application in diverse fields, from pharmacology to the development of new materials, the critical interpretation of such properties for their crucial role in the reactivity of these substances is of great interest. Knowledge on these thermodynamic data for key compounds is also relevant to the prediction and understanding of the properties and behavior of other parent compounds

Synthesis and thermochemical study of quinoxaline-N-oxides: enthalpies of dissociation of the N-O bond

The synthesis of three new quinoxaline mono-N-oxides derivatives, namely, 2-tert-butoxycarbonyl-3-methylquinoxaline-N-oxide, 2-phenylcarbamoyl-3-ethylquinoxaline-N-oxide, and 2-carbamoyl-3-methylquinoxaline-N-oxide, from their corresponding 1,4-di-N-oxides is reported. Samples of these compounds were used for a thermochemical study, which allowed derivation of their gaseous standard molar enthalpies of formation, Delta fHmo(g), from their enthalpies of formation in the condensed phase, Delta fHmo(cr), determined by static bomb combustion calorimetry, and from their enthalpies of sublimation, Delta crgHmo, determined by Calvet microcalorimetry. Finally, combining the Delta fHmo(g) for the quinoxaline-N-oxides derived in this work with literature values for the corresponding 1,4-di-N-oxides and atomic oxygen, the bond dissociation enthalpies for cleavage of the first N-O bond in the di-N-oxides, DH1(NO), were obtained and compared with existing data. Copyright (c) 2011 John Wiley & Sons, Ltd

ACE2-angiotensin-(1-7)-Mas axis in renal ischaemia/reperfusion injury in rats

AngII (angiotensin II), ACE (angiotensin I-converting enzyme) and the AT(1) receptor (AngII type I receptor) are associated with the inflammatory process and microvascular dysfunction of AKI (acute kidney injury) induced by renal I/R (ischaemia/reperfusion). However, Ang-(1-7) [angiotensin-(1-7)], ACE2 (angiotensin I-converting enzyme 2) and the Mas receptor also play a role in renal disease models. Therefore, in the present study, we have examined the renal profile of Ang-(1-7), ACE2 and the Mas receptor in renal I/R and compared them with that of AngII, ACE and the AT(1) receptor. Male Wistar rats were submitted to left nephrectomy and ischaemia (45 min) followed by reperfusion (2 or 4 h) in the right kidney. At 4 h of reperfusion, renal AngII was increased (P < 0.01) and renal Ang-(1-7) was decreased substantially (P < 0.05), although plasma levels of both angiotensins were unchanged. in addition, renal I/R decreased the renal mRNA expression of renin (P < 0.05), AT(1) receptors (P < 0.001) and ACE2 (P < 0.05). At 2 and 4 h of reperfusion, renal ACE activity was reduced (P < 0.05). On the other hand, renal expression of the Mas receptor was greatly increased at 4 h of reperfusion (P < 0.01), which was confirmed by immunohistochemical and Western blot analysis. in conclusion, increased renal expression of the Mas receptor associated with changes in the RAS (renin-angiotensin-system)-related peptidases support an important role for the ACE2 Ang-(1-7) Mas axis in AKI.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG)Univ Fed Minas Gerais, Inst Biol Sci, Dept Physiol & Biophys, BR-31270901 Belo Horizonte, MG, BrazilUniversidade Federal de São Paulo, Escola Paulista Med, Dept Biophys, BR-04044020 São Paulo, SP, BrazilUniv Fed Minas Gerais, Dept Pathol, BR-31270901 Belo Horizonte, MG, BrazilUniv Fed Minas Gerais, Dept Microbiol, BR-31270901 Belo Horizonte, MG, BrazilUniv Fed Minas Gerais, Clin Pathol Unit COLTEC, BR-31270901 Belo Horizonte, MG, BrazilUniv Fed Minas Gerais, Dept Biochem, Inst Biol Sci, BR-31270901 Belo Horizonte, MG, BrazilUniv Fed Minas Gerais, Dept Pediat, Fac Med, BR-31270901 Belo Horizonte, MG, BrazilUniversidade Federal de São Paulo, Escola Paulista Med, Dept Biophys, BR-04044020 São Paulo, SP, BrazilCAPES: PRDEX2009CNPq: 8701480/1997-4FAPEMIG: CBS 2044/96Web of Scienc

Energetic and structural characterization of 2-R-3-methylquinoxaline-1,4-dioxides (R = benzoyl or tert-butoxycarbonyl): experimental and computational studies

The gaseous standard molar enthalpies of formation of two 2-R-3-methylquinoxaline-1,4-dioxides (R = benzoyl or tert-butoxycarbonyl), at T = 298.15 K, were derived using the values for the enthalpies of formation of the compounds in the condensed phase, measured by static bomb combustion calorimetry, and for the enthalpies of sublimation, measured by Knudsen effusion, using a quartz crystal oscillator. The three dimensional structure of 2-tert-butoxycarbonyl-3-methylquinoxaline-1,4-dioxide has been obtained by X-ray crystallography showing that the two N-O bond lengths in this compound are identical. The experimentally determined geometry in the crystal is similar to that obtained in the gas-phase after computations performed at the B3LYP/6-311 + G(2d,2p) level of theory. The experimental and computational results reported allow to extend the discussion about the influence of the molecular structure on the dissociation enthalpy of the N-O bonds for quinoxaline 1,4-dioxide derivatives. As found previously, similar N-O bond lengths in quinoxaline-1,4-dioxide compounds are not linked with N-O bonds having the same strength. Copyright (c) 2007 John Wiley & Sons, Ltd

Enzyme replacement therapy with galsulfase in 34 children younger than five years of age with MPS VI

Background: Mucopolysaccharidosis type VI (MPS VI) is a progressive, chronic and multisystem lysosomal storage disease with a wide disease spectrum. Clinical and biochemical improvements have been reported for MPS VI patients on enzyme replacement therapy (ERT) with rhASB (recombinant human arylsulfatase B; galsulfase, Naglazyme (R), BioMarin Pharmaceutical Inc.), making early diagnosis and intervention imperative for optimal patient outcomes. Few studies have included children younger than five years of age. This report describes 34 MPS VI patients that started treatment with galsulfase before five years of age.Methods: Data from patients who initiated treatment at <5 years of age were collected from patients' medical records. Baseline and follow-up assessments of common symptoms that led to diagnosis and that were used to evaluate disease progression and treatment efficacy were evaluated.Results: A significant negative correlation was seen with treatment with ERT and urinary GAG levels. of those with baseline and follow-up growth data, 47% remained on their pre-treatment growth curve or moved to a higher percentile after treatment. of the 9 patients with baseline and follow-up sleep studies, 5 remained unaffected and 1 patient initially with mild sleep apnea showed improvement. Data regarding cardiac, ophthalmic, central nervous system, hearing, surgical interventions and development are also reported. No patient discontinued treatment due to an adverse event and all that were treatment-emergent resolved.Conclusions: the prescribed dosage of 1 mg/kg IV weekly with galsulfase ERT is shown to be safe and effective in slowing and/or improving certain aspects of the disease, although patients should be closely monitored for complications associated with the natural history of the disease, especially cardiac valve involvement and spinal cord compression. A long-term follow-up investigation of this group of children will provide further information on the benefits of early treatment as well as disease progression and treatment efficacy and safety in this young patient population. (C) 2013 Elsevier Inc. All rights reserved.BioMarin Pharmaceutical Inc.ShireGenzymeBioMarinFiocruz MS, Inst Nacl Saude Mulher Crianca & Adolescente Fern, Ctr Genet Med, BR-22250020 Rio de Janeiro, RJ, BrazilUniv Fed Bahia, Serv Genet Med, Salvador, BA, BrazilHosp Albert Sabin, Fortaleza, Ceara, BrazilUniv Fed Mato Grosso do Sul, Fac Med, Campo Grande, MS USAUniv São Paulo, Inst Crianca, São Paulo, BrazilHosp Barao de Lucena, Recife, PE, BrazilUniv Fed Parana, Hosp Clin, BR-80060000 Curitiba, Parana, BrazilCtr Reabilitacao Infantil, Natal, RN, BrazilHosp Univ Maranhao, Sao Luis, MA, BrazilUniversidade Federal de São Paulo, Ctr Referencia Erros Inatos Metab, São Paulo, SP, BrazilHosp São Paulo, Enzyme Replacement Therapy Serv, Hosp & Maternidade Celso Pierro, São Paulo, BrazilUniv Fed Rio Grande do Norte, HOSPED, Hosp Pediat Prof Heriberto Ferreira Bezerra, Natal, RN, BrazilUniv Fortaleza, Fortaleza, Ceara, BrazilUniv Fed Rio Grande do Norte, BR-59072970 Natal, RN, BrazilUniv Fed Triangulo Mineiro, Uberaba, MG, BrazilHosp Clin Acre, Rio Branco, AC, BrazilUniv Fed Espirito Santo, HUCAM, Vitoria, ES, BrazilUniversidade Federal de São Paulo, Ctr Referencia Erros Inatos Metab, São Paulo, SP, BrazilHosp São Paulo, Enzyme Replacement Therapy Serv, Hosp & Maternidade Celso Pierro, São Paulo, BrazilWeb of Scienc