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1.
J Chem Phys ; 159(19)2023 Nov 21.
Artigo em Inglês | MEDLINE | ID: mdl-37987519

RESUMO

Pheophytin a and chlorophyll a have been investigated by electrospray mass spectrometry in the positive and negative modes, in view of the importance of the knowledge of their properties in photosynthesis. Pheophytin and chlorophyll are both observed intensely in the protonated mode, and their main fragmentation route is the loss of their phytyl chain. Pheophytin is observed intact in the negative mode, while under collisions, it is primarily cleaved beyond the phytyl chain and loses the attaching propionate group. Chlorophyll is not detected in normal conditions in the negative mode, but addition of methanol solvent molecule is detected. Fragmentation of this adduct primarily forms a product (-30 amu) that dissociates into dephytyllated deprotonated chlorophyll. Semi-empirical molecular dynamics calculations show that the phytyl chain is unfolded from the chlorin cycle in pheophytin a and folded in chlorophyll a. Density functional theory calculations have been conducted to locate the charges on protonated and deprotonated pheophytin a and chlorophyll a and have found the major location sites that are notably more stable in energy by more than 0.5 eV than the others. The deprotonation site is found identical for pheophytin a and the chlorophyll a-methanol adduct. This is in line with experiment and calculation locating the addition of methanol on a double bond of deprotonated chlorophyll a.

2.
Phys Chem Chem Phys ; 18(23): 15609-18, 2016 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-27220613

RESUMO

In this work, we have performed molecular dynamics simulations using a hybrid Quantum Mechanics/Molecular Mechanics (QM/MM) scheme to study the mechanism of l-lactate oxidation by flavocytochrome b2 (Fcb2). Our results obtained at the QM(AM1)/MM level have been improved by single-point corrections using density functional theory (DFT) methods. Free energy surfaces have been calculated in the framework of the hydride transfer hypothesis. This mechanism involves the transfer of the lactate hydroxyl proton to H373 while the substrate αH atom is transferred as a hydride to the flavin mononucleotide (FMN) prosthetic group anchored in the active site. Four different systems have been modeled: wild-type enzyme considering R289 in a distal or a proximal conformation observed in crystal structures and the D282N and Y254L variants (with R289 in a distal position). Simulation results highlight the influence of the environment on the catalytic mechanism by describing a step-wise process in the WT enzyme with R289 in a distal position and a concerted mechanism for the other systems. In the step-wise mechanism, the hydride transfer to flavin can occur only after a proton transfer from substrate to H373. Modifications of the electrostatic field around l-lactate or H373 disfavor the highly charged complex resulting from this proton transfer. Simulations of the Y254L variant also reveal some effect of steric changes.

3.
Phys Chem Chem Phys ; 17(46): 30889-903, 2015 Dec 14.
Artigo em Inglês | MEDLINE | ID: mdl-26041466

RESUMO

The quantum dynamics of electron transfer in mixed-valence organic compounds is investigated using a reaction path model calibrated by constrained density functional theory (cDFT). Constrained DFT is used to define diabatic states relevant for describing the electron transfer, to obtain equilibrium structures for each of these states and to estimate the electronic coupling between them. The harmonic analysis at the diabatic minima yields normal modes forming the dissipative bath coupled to the electronic states. In order to decrease the system-bath coupling, an effective one dimensional vibronic Hamiltonian is constructed by partitioning the modes into a linear reaction path which connects both equilibrium positions and a set of secondary vibrational modes, coupled to this reaction coordinate. Using this vibronic model Hamiltonian, dissipative quantum dynamics is carried out using Redfield theory, based on a spectral density which is determined from the cDFT results. In a first benchmark case, the model is applied to a series of mixed-valence organic compounds formed by two 1,4-dimethoxy-3-methylphenylene fragments linked by an increasing number of phenylene bridges. This allows us to examine the coherent electron transfer in extreme situations leading to a ground adiabatic state with or without a barrier and therefore to the trapping of the charge or to an easy delocalization.


Assuntos
Compostos Orgânicos/química , Teoria Quântica , Transporte de Elétrons , Elétrons , Modelos Químicos , Temperatura
4.
Interdiscip Sci ; 2(1): 3-11, 2010 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-20396590

RESUMO

Following our previous study (Piquemal et al., New J. Chem., 2003, 27, 909), we present here a DFT study of the inhibition of the Tyrosinase enzyme. Broken-symmetry DFT computations are supplemented with Spin-Flip TD-DFT calculations, which, for the first time, are applied to such a dicopper enzyme. The chosen biomimetic model encompasses a dioxygen molecule, two Cu(II) cations, and six imidazole rings. The docking energy of a natural substrate, namely phenolate, together with those of several inhibitor and non-inhibitor compounds, are reported and show the ability of the model to rank the most potent inhibitors in agreement with experimental data. With respect to broken-symmetry calculations, the Spin-Flip TD-DFT approach reinforces the possibility for theory to point out potent inhibitors: the need for the deprotonation of the substrates, natural or inhibitors, is now clearly established. Moreover, Electron Localization Function (ELF) topological analysis computations are used to deeply track the particular electronic distribution of the Cu-O-Cu three-center bonds involved in the enzymatic Cu(2)O(2) metallic core (Piquemal and Pilmé, J. Mol. Struct.: Theochem, 2006, 77, 764). It is shown that such bonds exhibit very resilient out-of-plane density expansions that play a key role in docking interactions: their 3D-orientation could be the topological electronic signature of oxygen activation within such systems.


Assuntos
Monofenol Mono-Oxigenase/química , Ligação Competitiva , Domínio Catalítico , Química Farmacêutica/métodos , Biologia Computacional/métodos , Simulação por Computador , Cobre/química , Desenho de Fármacos , Imidazóis/química , Modelos Químicos , Modelos Moleculares , Modelos Teóricos , Conformação Molecular , Ligação Proteica , Software
5.
G Chir ; 20(10): 436-9, 1999 Oct.
Artigo em Italiano | MEDLINE | ID: mdl-10555415

RESUMO

The Authors report their results in 219 patients who underwent endoscopic polypectomy for benign adenomatous polyps and early colorectal cancer. This is safe and curative technique associated with low-risk of complications and in an ideal therapy to prevent the development of colorectal cancer. In fact, nowadays, dysplasia-carcinoma sequence has been described. All polyps were histologically identified and the grade of dysplasia always detected.


Assuntos
Adenocarcinoma/cirurgia , Adenoma/cirurgia , Pólipos do Colo/cirurgia , Neoplasias Colorretais/cirurgia , Pólipos Intestinais/cirurgia , Adenocarcinoma/patologia , Adenoma/patologia , Adulto , Idoso , Idoso de 80 Anos ou mais , Pólipos do Colo/patologia , Colonoscopia , Neoplasias Colorretais/patologia , Endoscopia , Feminino , Humanos , Pólipos Intestinais/patologia , Masculino , Pessoa de Meia-Idade , Estadiamento de Neoplasias
6.
G Chir ; 20(1-2): 51-2, 1999.
Artigo em Italiano | MEDLINE | ID: mdl-10097457

RESUMO

The Authors report their experience with the use of the Olympus Endoloop HX-20L for the prevention of haemorrhages after endoscopic polypectomy. They emphasize the utility of this therapeutic device that will find its right application only in a well selected group of patients.


Assuntos
Perda Sanguínea Cirúrgica/prevenção & controle , Pólipos do Colo/cirurgia , Endoscopia , Neoplasias do Colo Sigmoide/cirurgia , Adulto , Idoso , Idoso de 80 Anos ou mais , Colonoscopia , Endoscópios , Humanos , Ligadura/instrumentação , Ligadura/métodos , Pessoa de Meia-Idade
7.
Int Angiol ; 17(1): 1-9, 1998 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-9657240

RESUMO

To review the current status of clinical, pathological and arteriographic aspects of abdominal Takayasu's aortitis (TA). Personal experience with 86 patients with TA and review of the literature is the basis of this report. The diagnostic significance of primary versus secondary atherosclerosis is described in this communication and the arteriographic differential diagnostic guidelines are provided to separate abdominal TA from abdominal atherosclerosis.


Assuntos
Arterite de Takayasu , Angiografia , Aorta Abdominal , Doenças da Aorta/diagnóstico , Doenças da Aorta/diagnóstico por imagem , Arteriosclerose/diagnóstico , Arteriosclerose/diagnóstico por imagem , Diagnóstico Diferencial , Humanos , Arterite de Takayasu/diagnóstico , Arterite de Takayasu/diagnóstico por imagem
8.
ABCD (São Paulo, Impr.) ; 12(3/4): 39-40, Jul.-Dec. 1997.
Artigo em Inglês | LILACS | ID: lil-225826

RESUMO

O Helicobacter pylori tem sido considerado importante fator nas doencas gastroduodenais e o esquema chamado triplice e o que mais se aceita no momento para a sua terapeutica. Neste estudo incluiram-se 14 pacientes portadores de gastrite cronica, 30 com ulcera gastrica e 16 com ulcera duodenal. Foram divididos em 2 grupos homogeneos para tratamento clinico, cada um com esquema bem definido: grupo A - claritromicina 250mg/2, tinidazol 250mg/2 e omeprazole 20mg em caso de gastrite e 40mg em caso de ulcera; grupo B - mesmos antibioticos e ranitidina respectivamente nas doses de 150 e 300mg. O periodo de tratamento foi de 7 dias para gastrites e 4 semanas para ulceras. Atraves de endoscopia e biopsia realizadas 30 dias depois do termino do tratamento, os 30 casos do grupo A tiveram erradicacao completa do Helicobacter pylori e cicatrizacao das ulceras. No grupo B, apenas 3 casos nao tiveram eliminacao do Helicobacter pylori. Concluiu-se que o uso de bloqueadores H2 no lugar de inibidores da bomba protonica tambem permite a obtencao de sucesso terapeutico


Assuntos
Humanos , Tinidazol/administração & dosagem , Tinidazol/antagonistas & inibidores , Tinidazol/uso terapêutico , Helicobacter pylori/efeitos dos fármacos , Claritromicina/administração & dosagem , Claritromicina/antagonistas & inibidores , Claritromicina/uso terapêutico , Antiulcerosos/uso terapêutico , Úlcera Duodenal/terapia , Úlcera Gástrica/terapia , Ranitidina/administração & dosagem , Ranitidina/uso terapêutico , Omeprazol/administração & dosagem , Omeprazol/uso terapêutico , Seguimentos , Endoscopia do Sistema Digestório , Bombas de Próton/uso terapêutico , Dispepsia/terapia , Gastrite/terapia , Antagonistas dos Receptores H2 da Histamina/uso terapêutico
10.
Phys Rev A ; 45(2): 913-921, 1992 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-9907057
11.
Actual Odontostomatol (Paris) ; 45(173): 93-9, 1991 Mar.
Artigo em Francês | MEDLINE | ID: mdl-1853750

RESUMO

The author has shown that any impression material and its support in the mouth must be more malleable than the material used for the object to be reproduced. From a fall mandibular arch the impression of both sides, left and right, are taken successively by hemi-impressions without impression trays. Two individual half impression trays are made, placed in the mouth and are joined together using an auto-polymerizing resin. The resulting individual tray permits to make a perfect mucostatic impression. This method, far from taking more time, is a time saver, since the touch-ups to the individual tray and then to the finished prosthesis are practically non-existent or considerably reduced.


Assuntos
Técnica de Moldagem Odontológica , Prótese Total Inferior , Humanos , Arcada Edêntula , Mandíbula
12.
Clin Pediatr (Phila) ; 28(6): 261-4, 1989 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-2656052

RESUMO

The chest roentgenogram is an accepted tool for the diagnosis of pneumonia. Little information is available, however, addressing the ability of physicians to distinguish bacterial from nonbacterial pneumonias by examination of the chest roentgenogram. Five different observers evaluated 36 chest films from patients with pneumonia who had a laboratory proven etiologic diagnosis. The sensitivity of roentgenogram diagnosis of bacterial pneumonia ranged from 42-58 percent. When clinical and laboratory data were provided to the observers the sensitivity ranged from 42-92 percent. This study indicates that chest film examination is too insensitive to be useful for the selection of patients who have bacterial pneumonia from those whose pneumonia is non-bacterial.


Assuntos
Infecções Bacterianas , Pneumonia/diagnóstico por imagem , Adolescente , Infecções Bacterianas/diagnóstico por imagem , Criança , Pré-Escolar , Diagnóstico Diferencial , Humanos , Lactente , Pneumonia/etiologia , Pneumonia Viral/diagnóstico por imagem , Radiografia , Sensibilidade e Especificidade
14.
J Pediatr ; 111(2): 194-200, 1987 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-3612389

RESUMO

The cause and clinical manifestations of pneumonia were studied in 98 pediatric outpatients. A viral diagnosis was established in 38 (39%) of the 98 patients, and a bacterial diagnosis in 19 (19%). Ten (53%) of the 19 patients with bacterial pneumonia had a concurrent viral infection. No clinical, laboratory, or radiographic findings that would reliably differentiate viral from bacterial infection were identified. This study suggests that bacterial pneumonia is more common in pediatric outpatients than previously reported, and that the clinical, laboratory, and radiographic findings in patients with bacterial infection may be indistinguishable from findings in patients with viral infection.


Assuntos
Assistência Ambulatorial , Pneumonia/etiologia , Adolescente , Antígenos de Bactérias/análise , Antígenos Virais/análise , California , Criança , Pré-Escolar , Contraimunoeletroforese , Humanos , Lactente , Nasofaringe/microbiologia , Faringe/microbiologia , Pneumonia/diagnóstico , Pneumonia/microbiologia , Pneumonia Viral/diagnóstico , Pneumonia Viral/etiologia , Pneumonia Viral/microbiologia , Cultura de Vírus
15.
Phys Rev Lett ; 54(14): 1469-1471, 1985 Apr 08.
Artigo em Inglês | MEDLINE | ID: mdl-10031046
17.
J Adolesc Health Care ; 5(3): 207-9, 1984 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-6735837

RESUMO

Acute epiglottitis is rare in adolescents. Respiratory compromise may not occur early. Physicians should consider this diagnosis in their adolescent patients who complain of pain and dysphagia, with or without visible pharyngitis. Airway maintenance is paramount. The antibiotic used should include coverage for Hemophilus influenzae, type B. The case presented here illustrates these points.


Assuntos
Epiglotite/diagnóstico , Laringite/diagnóstico , Doença Aguda , Adolescente , Ampicilina/uso terapêutico , Cloranfenicol/uso terapêutico , Diagnóstico Diferencial , Quimioterapia Combinada , Epiglotite/tratamento farmacológico , Humanos , Masculino
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