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[PMID]:28238040
[Au] Autor:Wang X; Neufurth M; Tolba E; Wang S; Schröder HC; Müller WE
[Ad] Endereço:ERC Advanced Investigator Group, Institute for Physiological Chemistry, University Medical Center of the Johannes Gutenberg University, Duesbergweg 6, 55128, Mainz, Germany. wang013@uni-mainz.de.
[Ti] Título:Biocalcite and Carbonic Acid Activators.
[So] Source:Prog Mol Subcell Biol;55:221-257, 2017.
[Is] ISSN:0079-6484
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:Based on evolution of biomineralizing systems and energetic considerations, there is now compelling evidence that enzymes play a driving role in the formation of the inorganic skeletons from the simplest animals, the sponges, up to humans. Focusing on skeletons based on calcium minerals, the principle enzymes involved are the carbonic anhydrase (formation of the calcium carbonate-based skeletons of many invertebrates like the calcareous sponges, as well as deposition of the calcium carbonate bioseeds during human bone formation) and the alkaline phosphatase (providing the phosphate for bone calcium phosphate-hydroxyapatite formation). These two enzymes, both being involved in human bone formation, open novel not yet exploited targets for pharmacological intervention of human bone diseases like osteoporosis, using compounds that act as activators of these enzymes. This chapter focuses on carbonic anhydrases of biomedical interest and the search for potential activators of these enzymes, was well as the interplay between carbonic anhydrase-mediated calcium carbonate bioseed synthesis and metabolism of energy-rich inorganic polyphosphates. Beyond that, the combination of the two metabolic products, calcium carbonate and calcium-polyphosphate, if applied in an amorphous form, turned out to provide the basis for a new generation of scaffold materials for bone tissue engineering and repair that are, for the first time, morphogenetically active.
[Mh] Termos MeSH primário: Fosfatase Alcalina/metabolismo
Desenvolvimento Ósseo/efeitos dos fármacos
Osso e Ossos/enzimologia
Carbonato de Cálcio/metabolismo
Fosfatos de Cálcio/metabolismo
Anidrases Carbônicas/metabolismo
[Mh] Termos MeSH secundário: Fosfatase Alcalina/efeitos dos fármacos
Animais
Produtos Biológicos/química
Produtos Biológicos/farmacologia
Osso e Ossos/efeitos dos fármacos
Ácido Carbônico/metabolismo
Anidrases Carbônicas/efeitos dos fármacos
Avaliação Pré-Clínica de Medicamentos/tendências
Ativação Enzimática/efeitos dos fármacos
Seres Humanos
Poríferos/química
[Pt] Tipo de publicação:JOURNAL ARTICLE; RESEARCH SUPPORT, NON-U.S. GOV'T
[Nm] Nome de substância:
0 (Biological Products); 0 (Calcium Phosphates); 463-79-6 (Carbonic Acid); EC 3.1.3.1 (Alkaline Phosphatase); EC 4.2.1.1 (Carbonic Anhydrases); H0G9379FGK (Calcium Carbonate)
[Em] Mês de entrada:1706
[Cu] Atualização por classe:170616
[Lr] Data última revisão:
170616
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:170227
[St] Status:MEDLINE
[do] DOI:10.1007/978-3-319-51284-6_7


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[PMID]:27699824
[Au] Autor:Takácsi-Nagy A; Kilár F; Thormann W
[Ad] Endereço:Institute of Bioanalysis and Szentágothai Research Center, University of Pécs, Pécs, Hungary.
[Ti] Título:Modeling of formation and prevention of a pure water zone in capillary isoelectric focusing with narrow pH range carrier ampholytes.
[So] Source:Electrophoresis;38(5):677-688, 2017 03.
[Is] ISSN:1522-2683
[Cp] País de publicação:Germany
[La] Idioma:eng
[Ab] Resumo:This paper comprises a continuation of computer simulation studies dealing with carrier ampholyte based CIEF in presence of narrow pH gradients. With this technique, amphoteric sample components with pI values outside the pH gradient are migrating isotachophoretically toward the cathode or anode whereas components with pI values within the gradient become focused. In order to understand the processes occurring in presence of the electric field, the behavior of both carrier ampholytes and amphoteric sample components is investigated by computer modeling. Characteristics of two pH unit gradients with end components having pI values at or around 7.00 and conditions that lead to the formation of a water zone at neutrality were investigated. Data obtained reveal that a zone of water is formed in focusing with carrier ampholytes when the applied pH range does not cover the neutral region, ends at pH 7.00 or begins at pH 7.00. The presence of additional amphoteric components that cover the neutrality region prevent water zone formation under current flow. This situation is met in experiments with narrow pH gradients that end or begin around neutrality. Simulation data reveal that no water zone evolves when atmospheric carbon dioxide dissolved in the catholyte causes the migration of carbonic acid (in the form of carbonate and/or hydrogen carbonate ions) from the catholyte through the focusing structure. An electrolyte change in the electrode solution does not have an impact on the focusing part but does change the isotachophoretic pattern migrating behind the leading ion.
[Mh] Termos MeSH primário: Misturas Anfolíticas/química
Eletroforese Capilar/métodos
Focalização Isoelétrica/métodos
[Mh] Termos MeSH secundário: Ácido Carbônico/química
Simulação por Computador
Concentração de Íons de Hidrogênio
Água/química
[Pt] Tipo de publicação:JOURNAL ARTICLE; RESEARCH SUPPORT, NON-U.S. GOV'T
[Nm] Nome de substância:
0 (Ampholyte Mixtures); 059QF0KO0R (Water); 463-79-6 (Carbonic Acid)
[Em] Mês de entrada:1709
[Cu] Atualização por classe:171106
[Lr] Data última revisão:
171106
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:161005
[St] Status:MEDLINE
[do] DOI:10.1002/elps.201600314


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[PMID]:27595724
[Au] Autor:Abraham S; Kamble AB; Gupta P; Satpute A; Chaudhari S; Ladhe P
[Ad] Endereço:Professor and Head, Department of Conservative Dentistry and Endodontics, SMBT Dental College and Hospital, Sangamner, Maharashtra, India, Phone: +917798686067, e-mail: abrahamsathish@yahoo.in.
[Ti] Título:In vitro Evaluation of the Efficacy of 2% Carbonic Acid and 2% Acetic Acid on Retrieval of Mineral Trioxide Aggregate and their Effect on Microhardness of Dentin.
[So] Source:J Contemp Dent Pract;17(7):568-73, 2016 Jul 01.
[Is] ISSN:1526-3711
[Cp] País de publicação:India
[La] Idioma:eng
[Ab] Resumo:INTRODUCTION: In this in vitro study, the efficacy of 2% carbonic acid and 2% acetic acid on the surface, microhardness of white mineral trioxide aggregate (MTA) and dentin after 1 day of setting and 21 days of setting of MTA is measured. MATERIALS AND METHODS: Tooth molds were made using 60 single-rooted premolars by slicing them to 4 mm in the mid-root region. White MTA (Angelus) was mixed and packed in the molds. Three experimental groups were formed and exposed to 2% carbonic acid, 2% acetic acid, and saline for 10 minutes on 1 and 21 days of setting respectively. Vickers hardness test of white MTA and dentin was done before and after exposure. Data were subjected to analysis of variance (ANOVA) and post hoc tests. RESULTS: The results show that 2% acetic acid was significantly effective in reducing the microhardness of white MTA compared to 2% carbonic acid and saline on exposure for 10 minutes. CONCLUSION: The results of the present study indicate that 2% acetic acid has maximum efficacy in reducing the surface microhardness of partial and completely set MTA, followed by 2% carbonic acid. CLINICAL SIGNIFICANCE: The following study will help find an adjunct for retrieval of MTA, which was found difficult with the existing methods.
[Mh] Termos MeSH primário: Ácido Acético/química
Compostos de Alumínio/química
Compostos de Cálcio/química
Ácido Carbônico/química
Dentina/efeitos dos fármacos
Óxidos/química
Materiais Restauradores do Canal Radicular/química
Silicatos/química
[Mh] Termos MeSH secundário: Dente Pré-Molar
Combinação de Medicamentos
Dureza
Técnicas In Vitro
Propriedades de Superfície
[Pt] Tipo de publicação:JOURNAL ARTICLE
[Nm] Nome de substância:
0 (Aluminum Compounds); 0 (Calcium Compounds); 0 (Drug Combinations); 0 (Oxides); 0 (Root Canal Filling Materials); 0 (Silicates); 0 (mineral trioxide aggregate); 463-79-6 (Carbonic Acid); Q40Q9N063P (Acetic Acid)
[Em] Mês de entrada:1710
[Cu] Atualização por classe:171030
[Lr] Data última revisão:
171030
[Sb] Subgrupo de revista:D; IM
[Da] Data de entrada para processamento:160907
[St] Status:MEDLINE


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[PMID]:27419241
[Au] Autor:Lacerda-Santos R; Sampaio GA; Moura Mde F; Carvalho FG; Santos AD; Pithon MM; Alves PM
[Ti] Título:Effect of Different Concentrations of Chlorhexidine in Glass-ionomer Cements on In Vivo Biocompatibility.
[So] Source:J Adhes Dent;18(4):325-30, 2016.
[Is] ISSN:1461-5185
[Cp] País de publicação:England
[La] Idioma:eng
[Ab] Resumo:PURPOSE: To examine whether a difference exists between the in vivo biocompatibility of glass-ionomer cements (GICs) containing chlorhexidine (CHX) in different concentrations. MATERIALS AND METHODS: Eighty-four male Wistar rats were distributed into 7 groups (n = 12) and received subcutaneous implants of small tubes containing different materials, as follows: Ketac control (K), Ketac-CHX 10% (K10), Ketac-CHX 18% (K18), Resilience control (R), Resilience-CHX 10% (R10), Resilience-CHX 18% (R18), Control (polyethylene). The animals were then sacrificed on post-insertion days 7, 15 and 30, and tissues were examined under an optical microscope for inflammatory infiltrate, edema, necrosis, granulation tissue, multinucleated giant cells, and collagen fibers. The results were statistically analyzed using Kruskal-Wallis and Dunn's tests (p < 0.05). RESULTS: Groups K18 and R18 showed larger areas of intense inflammatory infiltrate, with significant differences between group C and groups K18 and R18 (p = 0.007) at 7 days, and between groups C and K18 (p = 0.017) at 15 days. In terms of tissue repair, groups K18 and R18 demonstrated a lower quantity of collagen fibers with significant differences from group C (p = 0.019) at 7 days, and between group K18 and group C (p = 0.021) at 15 days. CONCLUSION: The 18% concentration of CHX was shown to have a toxic effect. The 10% concentration of CHX was shown to be suitable for tissue contact. The addition of CHX to the glass-ionomer cements is a highly promising method for obtaining of an antibacterial GIC for use in clinical practice.
[Mh] Termos MeSH primário: Anti-Infecciosos Locais/administração & dosagem
Materiais Biocompatíveis/toxicidade
Clorexidina/administração & dosagem
Cimentos de Ionômeros de Vidro/toxicidade
[Mh] Termos MeSH secundário: Resinas Acrílicas/química
Resinas Acrílicas/toxicidade
Animais
Anti-Infecciosos Locais/química
Anti-Infecciosos Locais/toxicidade
Materiais Biocompatíveis/química
Ácido Carbônico/química
Ácido Carbônico/toxicidade
Clorexidina/química
Clorexidina/toxicidade
Colágeno/efeitos dos fármacos
Materiais Dentários/química
Materiais Dentários/toxicidade
Edema/induzido quimicamente
Fibroblastos/efeitos dos fármacos
Células Gigantes/efeitos dos fármacos
Cimentos de Ionômeros de Vidro/química
Tecido de Granulação/efeitos dos fármacos
Óxido de Magnésio/química
Óxido de Magnésio/toxicidade
Masculino
Teste de Materiais
Necrose
Cimento de Policarboxilato/química
Cimento de Policarboxilato/toxicidade
Polietileno/química
Distribuição Aleatória
Ratos
Tela Subcutânea/efeitos dos fármacos
Óxido de Zinco/química
Óxido de Zinco/toxicidade
[Pt] Tipo de publicação:COMPARATIVE STUDY; JOURNAL ARTICLE
[Nm] Nome de substância:
0 (Acrylic Resins); 0 (Anti-Infective Agents, Local); 0 (Biocompatible Materials); 0 (Dental Materials); 0 (Glass Ionomer Cements); 0 (Polycarboxylate Cement); 3A3U0GI71G (Magnesium Oxide); 463-79-6 (Carbonic Acid); 4Q93RCW27E (carbopol 940); 86473-14-5 (Ketac-cem); 9002-88-4 (Polyethylene); 9007-34-5 (Collagen); R4KO0DY52L (Chlorhexidine); SOI2LOH54Z (Zinc Oxide)
[Em] Mês de entrada:1701
[Cu] Atualização por classe:170107
[Lr] Data última revisão:
170107
[Sb] Subgrupo de revista:D
[Da] Data de entrada para processamento:160716
[St] Status:MEDLINE
[do] DOI:10.3290/j.jad.a36512


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[PMID]:27410514
[Au] Autor:Mioni R; Marega A; Lo Cicero M; Montanaro D
[Ad] Endereço:a Division of Nephrology , Civil and University Hospital , Santa Maria Della Misericordia , Udine , Italy.
[Ti] Título:Old and new approaches to the interpretation of acid-base metabolism, starting from historical data applied to diabetic acidosis.
[So] Source:Scand J Clin Lab Invest;76(7):520-543, 2016 Nov.
[Is] ISSN:1502-7686
[Cp] País de publicação:England
[La] Idioma:eng
[Ab] Resumo:The approach to acid-base chemistry in medicine includes several methods. Currently, the two most popular procedures are derived from Stewart's studies and from the bicarbonate/BE-based classical formulation. Another method, unfortunately little known, follows the Kildeberg theory applied to acid-base titration. By using the data produced by Dana Atchley in 1933, regarding electrolytes and blood gas analysis applied to diabetes, we compared the three aforementioned methods, in order to highlight their strengths and their weaknesses. The results obtained, by reprocessing the data of Atchley, have shown that Kildeberg's approach, unlike the other two methods, is consistent, rational and complete for describing the organ-physiological behavior of the hydrogen ion turnover in human organism. In contrast, the data obtained using the Stewart approach and the bicarbonate-based classical formulation are misleading and fail to specify which organs or systems are involved in causing or maintaining the diabetic acidosis. Stewart's approach, despite being considered 'quantitative', does not propose in any way the concept of 'an amount of acid' and becomes even more confusing, because it is not clear how to distinguish between 'strong' and 'weak' ions. As for Stewart's approach, the classical method makes no distinction between hydrogen ions managed by the intermediate metabolism and hydroxyl ions handled by the kidney, but, at least, it is based on the concept of titration (base-excess) and indirectly defines the concept of 'an amount of acid'. In conclusion, only Kildeberg's approach offers a complete understanding of the causes and remedies against any type of acid-base disturbance.
[Mh] Termos MeSH primário: Cetoacidose Diabética/sangue
Cetoacidose Diabética/urina
Eletrólitos
Rim/metabolismo
Prótons
[Mh] Termos MeSH secundário: Equilíbrio Ácido-Base
Bicarbonatos/sangue
Bicarbonatos/urina
Gasometria
Ácido Carbônico/sangue
Ácido Carbônico/urina
Cetoacidose Diabética/história
Cetoacidose Diabética/fisiopatologia
Eletrólitos/sangue
Eletrólitos/urina
História do Século XX
História do Século XXI
Seres Humanos
Concentração de Íons de Hidrogênio
Hidróxidos/sangue
Hidróxidos/urina
Rim/fisiopatologia
[Pt] Tipo de publicação:HISTORICAL ARTICLE; JOURNAL ARTICLE
[Nm] Nome de substância:
0 (Bicarbonates); 0 (Electrolytes); 0 (Hydroxides); 0 (Protons); 463-79-6 (Carbonic Acid); 9159UV381P (hydroxide ion)
[Em] Mês de entrada:1703
[Cu] Atualização por classe:170817
[Lr] Data última revisão:
170817
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:160714
[St] Status:MEDLINE


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[PMID]:27111726
[Au] Autor:Dos Santos VB; Vidal DT; Francisco KJ; Ducati LC; do Lago CL
[Ad] Endereço:Department of Fundamental Chemistry, Institute of Chemistry, University of São Paulo, Av. Prof. Lineu Prestes, 748, São Paulo, SP 05508-000, Brazil.
[Ti] Título:Formation of isomers of anionic hemiesters of sugars and carbonic acid in aqueous medium.
[So] Source:Carbohydr Res;428:18-22, 2016 Jun 16.
[Is] ISSN:1873-426X
[Cp] País de publicação:Netherlands
[La] Idioma:eng
[Ab] Resumo:Hemiesters of carbonic acid can be freely formed in aqueous media containing HCO3(-)/CO2 and mono- or poly-hydroxy compounds. Herein, (13)C NMR spectroscopy was used to identify isomers formed in aqueous solutions of glycerol (a prototype compound) and seven carbohydrates, as well as to estimate the equilibrium constant of formation (Keq). Although both isomers are formed, glycerol 1-carbonate corresponds to 90% of the product. While fructose and ribose form an indistinct mixture of isomers, the anomers of d-glucopyranose 6-carbonate correspond to 74% of the eight isomers of glucose carbonate that were detected. The values of Keq for the disaccharides sucrose (4.3) and maltose (4.2) are about twice the values for the monosaccharides glucose (2.0) and fructose (2.3). Ribose (Keq = 0.89)-the only sugar without a significant concentration of a species containing a -CH2OH group in an aqueous solution-resulted in the smallest Keq. On the basis of the Keq value and the concentrations of HCO3(-) and glucose in blood, one can anticipate a concentration of 2-4 µmol L(-1) for glucose 6-carbonate, which corresponds to ca. of 10% of its phosphate counterpart (glucose 6-phosphate).
[Mh] Termos MeSH primário: Carboidratos/química
Ácido Carbônico/química
Ésteres/síntese química
[Mh] Termos MeSH secundário: Espectroscopia de Ressonância Magnética Nuclear de Carbono-13/métodos
Ésteres/química
Glicerol/química
Isomerismo
Estrutura Molecular
Água/química
[Pt] Tipo de publicação:JOURNAL ARTICLE
[Nm] Nome de substância:
0 (Carbohydrates); 0 (Esters); 059QF0KO0R (Water); 463-79-6 (Carbonic Acid); PDC6A3C0OX (Glycerol)
[Em] Mês de entrada:1702
[Cu] Atualização por classe:170203
[Lr] Data última revisão:
170203
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:160426
[St] Status:MEDLINE


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[PMID]:27078949
[Au] Autor:Sun PA; Yu S; Mo FZ; He SY; Lu JF; Yuan YQ
[Ti] Título:[Hydrochemical Characteristics and Influencing Factors in Different Geological Background: A Case Study in Darongjiang and Lingqu Basin, Guangxi, China].
[So] Source:Huan Jing Ke Xue;37(1):123-31, 2016 Jan 15.
[Is] ISSN:0250-3301
[Cp] País de publicação:China
[La] Idioma:chi
[Ab] Resumo:The observation and sampling were carried out in May 2013 to April 2014 in a hydrological year for two river basins with different geological background in upstream of Li river basin. The seasonal variations of river water chemistry and its main influencing factors were discussed in this paper. The results showed that the hydrochemistry types of both Darongjiang basin with 9% of carbonates and Lingqu basin with nearly 50% of carbonates in area belonged to Ca-HCO3 type. Ca2+ and HCO3- were the main cations and anions. The main ion concentrations were higher in winter and lower in summer, affected by the change of the flow. Ca2+, Mg2+, HCO3- were mainly sourced from the weathering of carbonates by carbonic acid. The weathering of carbonates by sulfuric acid and the weathering of silicate rocks also had contribution to the river water chemistry. In addition, comparing to the Lingqu basin, the contribution of the weathering of carbonates was much more than the percent of carbonates area, because the carbonate rocks were eroded by the allogenic water. On the other hand, K+, Na+, Cl-, NO3-, SO4(2-) were mainly affected by the atmospheric precipitation and human activities. Comparing to the Darongjiang Basin, the effects of human activities on the changes of K+, Na+, Cl-, NO3-, SO4(2-) were more significant in Lingqu Basin.
[Mh] Termos MeSH primário: Carbonatos/análise
Monitoramento Ambiental
Rios/química
Estações do Ano
[Mh] Termos MeSH secundário: Ácido Carbônico/análise
China
Geologia
Hidrologia
Ácidos Sulfúricos/análise
Tempo (Meteorologia)
[Pt] Tipo de publicação:ENGLISH ABSTRACT; JOURNAL ARTICLE
[Nm] Nome de substância:
0 (Carbonates); 0 (Sulfuric Acids); 463-79-6 (Carbonic Acid); O40UQP6WCF (sulfuric acid)
[Em] Mês de entrada:1605
[Cu] Atualização por classe:161018
[Lr] Data última revisão:
161018
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:160416
[St] Status:MEDLINE


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[PMID]:27008729
[Au] Autor:Tanis J; DiCorpo JE; Friedman D; Merlin M
[Ti] Título:BALANCING FOR LIFE. Correcting common acid-base imbalances using bicarbonate & CO2 exchange.
[So] Source:JEMS;41(2):38-42, 2016 Feb.
[Is] ISSN:0197-2510
[Cp] País de publicação:United States
[La] Idioma:eng
[Mh] Termos MeSH primário: Equilíbrio Ácido-Base/efeitos dos fármacos
Bicarbonatos/uso terapêutico
Ácido Carbônico/uso terapêutico
[Mh] Termos MeSH secundário: Bicarbonatos/farmacologia
Ácido Carbônico/farmacologia
Cuidados Críticos/métodos
Serviços Médicos de Emergência
Seres Humanos
[Pt] Tipo de publicação:JOURNAL ARTICLE
[Nm] Nome de substância:
0 (Bicarbonates); 463-79-6 (Carbonic Acid)
[Em] Mês de entrada:1605
[Cu] Atualização por classe:160324
[Lr] Data última revisão:
160324
[Sb] Subgrupo de revista:H
[Da] Data de entrada para processamento:160325
[St] Status:MEDLINE


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[PMID]:26879554
[Au] Autor:Daschakraborty S; Kiefer PM; Miller Y; Motro Y; Pines D; Pines E; Hynes JT
[Ad] Endereço:Department of Chemistry and Biochemistry, University of Colorado , Boulder, Colorado 80309-0215, United States.
[Ti] Título:Reaction Mechanism for Direct Proton Transfer from Carbonic Acid to a Strong Base in Aqueous Solution I: Acid and Base Coordinate and Charge Dynamics.
[So] Source:J Phys Chem B;120(9):2271-80, 2016 Mar 10.
[Is] ISSN:1520-5207
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:Protonation by carbonic acid H2CO3 of the strong base methylamine CH3NH2 in a neutral contact pair in aqueous solution is followed via Car-Parrinello molecular dynamics simulations. Proton transfer (PT) occurs to form an aqueous solvent-stabilized contact ion pair within 100 fs, a fast time scale associated with the compression of the acid-base hydrogen-bond (H-bond), a key reaction coordinate. This rapid barrierless PT is consistent with the carbonic acid-protonated base pKa difference that considerably favors the PT, and supports the view of intact carbonic acid as potentially important proton donor in assorted biological and environmental contexts. The charge redistribution within the H-bonded complex during PT supports a Mulliken picture of charge transfer from the nitrogen base to carbonic acid without altering the transferring hydrogen's charge from approximately midway between that of a hydrogen atom and that of a proton.
[Mh] Termos MeSH primário: Ácido Carbônico/química
[Mh] Termos MeSH secundário: Simulação de Dinâmica Molecular
Prótons
Soluções
Água/química
[Pt] Tipo de publicação:JOURNAL ARTICLE; RESEARCH SUPPORT, N.I.H., EXTRAMURAL; RESEARCH SUPPORT, NON-U.S. GOV'T; RESEARCH SUPPORT, U.S. GOV'T, NON-P.H.S.
[Nm] Nome de substância:
0 (Protons); 0 (Solutions); 059QF0KO0R (Water); 463-79-6 (Carbonic Acid)
[Em] Mês de entrada:1612
[Cu] Atualização por classe:161230
[Lr] Data última revisão:
161230
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:160217
[St] Status:MEDLINE
[do] DOI:10.1021/acs.jpcb.5b12742


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[PMID]:26876428
[Au] Autor:Daschakraborty S; Kiefer PM; Miller Y; Motro Y; Pines D; Pines E; Hynes JT
[Ad] Endereço:Department of Chemistry and Biochemistry, University of Colorado , Boulder, Colorado 80309-0215, United States.
[Ti] Título:Reaction Mechanism for Direct Proton Transfer from Carbonic Acid to a Strong Base in Aqueous Solution II: Solvent Coordinate-Dependent Reaction Path.
[So] Source:J Phys Chem B;120(9):2281-90, 2016 Mar 10.
[Is] ISSN:1520-5207
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:The protonation of methylamine base CH3NH2 by carbonic acid H2CO3 within a hydrogen (H)-bonded complex in aqueous solution was studied via Car-Parrinello dynamics in the preceding paper (Daschakraborty, S.; Kiefer, P. M.; Miller, Y.; Motro, Y.; Pines, D.; Pines, E.; Hynes, J. T. J. Phys. Chem. B 2016, DOI: 10.1021/acs.jpcb.5b12742). Here some important further details of the reaction path are presented, with specific emphasis on the water solvent's role. The overall reaction is barrierless and very rapid, on an ∼100 fs time scale, with the proton transfer (PT) event itself being very sudden (<10 fs). This transfer is preceded by the acid-base H-bond's compression, while the water solvent changes little until the actual PT occurrence; this results from the very strong driving force for the reaction, as indicated by the very favorable acid-protonated base ΔpKa difference. Further solvent rearrangement follows immediately the sudden PT's production of an incipient contact ion pair, stabilizing it by establishment of equilibrium solvation. The solvent water's short time scale ∼120 fs response to the incipient ion pair formation is primarily associated with librational modes and H-bond compression of water molecules around the carboxylate anion and the protonated base. This is consistent with this stabilization involving significant increase in H-bonding of hydration shell waters to the negatively charged carboxylate group oxygens' (especially the former H2CO3 donor oxygen) and the nitrogen of the positively charged protonated base's NH3(+).
[Mh] Termos MeSH primário: Ácido Carbônico/química
Solventes/química
Água/química
[Mh] Termos MeSH secundário: Ligações de Hidrogênio
Prótons
[Pt] Tipo de publicação:JOURNAL ARTICLE; RESEARCH SUPPORT, N.I.H., EXTRAMURAL; RESEARCH SUPPORT, NON-U.S. GOV'T; RESEARCH SUPPORT, U.S. GOV'T, NON-P.H.S.
[Nm] Nome de substância:
0 (Protons); 0 (Solvents); 059QF0KO0R (Water); 463-79-6 (Carbonic Acid)
[Em] Mês de entrada:1612
[Cu] Atualização por classe:161230
[Lr] Data última revisão:
161230
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:160216
[St] Status:MEDLINE
[do] DOI:10.1021/acs.jpcb.5b12744



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