Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 63
Filtrar
Mais filtros

Base de dados
País/Região como assunto
Tipo de documento
Intervalo de ano de publicação
1.
Public Health ; 201: 12-18, 2021 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-34742112

RESUMO

OBJECTIVES: This study aimed to evaluate the trend of stillbirth from 2009 to 2018. The causes of stillbirth were classified using the International Classification of Diseases - Perinatal Mortality (ICD-PM). STUDY DESIGN AND METHODS: A retrospective chart review was performed on 135 stillbirths from 2009 to 2018 in a tertiary university teaching hospital. The annual stillbirth rate was calculated, and the trend was evaluated. The cause of death was reclassified using ICD-PM. RESULTS: The stillbirth rate was 3.70 per 1000 total births, and it remained stable over the studied period (P = 0.238). Most of the stillbirth (97.8%) were antepartum deaths. The proportion of unexplained stillbirth was reduced from 57% to 18.5% after reclassified by ICD-PM coding. Another major cause of antepartum stillbirths was disorders related to fetal growth, which consisted of mothers with medical and surgical conditions (11%, n = 15, ICD-PM code A5, M4) or mothers with complications of placenta, cord and membranes (8.9%, n = 12, ICD-PM code A5, M1). CONCLUSION: The use of ICD-PM was useful in reducing the proportion of unexplained stillbirths. ICD-PM has the advantages of coding related to the timing of stillbirth and associated maternal conditions. Pitfalls including the unclear use of the code A3-'antepartum hypoxia,' guidance on coding of well-controlled maternal medical conditions and placental pathology and the importance of subcategorisation need to be addressed.


Assuntos
Mortalidade Perinatal , Natimorto , Causas de Morte , Feminino , Humanos , Classificação Internacional de Doenças , Placenta , Gravidez , Estudos Retrospectivos , Natimorto/epidemiologia
2.
Cytopathology ; 28(4): 299-306, 2017 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-28387003

RESUMO

OBJECTIVE: Intraperitoneal chemotherapy (IP ChT) is an emerging modality in the treatment of advanced gastric adenocarcinoma with peritoneal disease. Cytological evaluation of peritoneal fluid specimens from patients undergoing IP ChT is important in clinical management. However, direct intraperitoneal exposure to chemotherapeutic agents induces cytomorphological changes in benign constituents of peritoneal fluid, presenting particular challenges to accurate cytological interpretation. These morphological changes have not been well characterised in the literature. We systematically reviewed the cytomorphological features in immunocytochemically-confirmed positive and negative IP ChT peritoneal fluid samples to elucidate the degree of morphological overlap between malignant and reactive cells. METHODS: We reviewed 39 peritoneal fluid samples of patients treated with IP ChT, and scored specific cytomorphological parameters of both benign and malignant cells with the aid of relevant immunocytochemical interrogation. RESULTS: The present findings show a significant degree of morphological overlap between reactive and malignant cells. Abnormal, "exploding" mitotic figures, nuclear membrane irregularities, multi-nucleation and cytoplasmic vacuolation were commonly observed in negative fluid specimens. The most helpful feature that favoured malignant cells was the increased nuclear-to-cytoplasmic ratio. A background inflammatory milieu of eosinophils and/or neutrophils was seen in 45-58% of post IP ChT peritoneal fluid specimens. The presence of pseudoparakeratotic cells, a novel observation in post IP ChT fluid specimens is also described. CONCLUSIONS: The extent of reactive cytomorphological anomalies arising from treatment with IP ChT poses unique diagnostic challenges and may prompt a malignant or 'atypical' diagnosis in benign reactive samples.


Assuntos
Líquido Ascítico/patologia , Citodiagnóstico/métodos , Neoplasias Peritoneais/tratamento farmacológico , Núcleo Celular/patologia , Estudos de Coortes , Humanos , Imuno-Histoquímica , Inflamação/patologia , Injeções Intraperitoneais , Neoplasias Peritoneais/diagnóstico , Neoplasias Peritoneais/patologia
3.
Dermatol Online J ; 22(4)2016 Apr 18.
Artigo em Inglês | MEDLINE | ID: mdl-27617464

RESUMO

Acral pseudolymphomatous angiokeratoma of children (APACHE) is a rare form of cutaneous pseudolymphoma characterized byangiomatous papules with a predilection for the acral regions of children. Classically, a dense dermal lymphocytic infiltrate composed of both T and B cells is seen in histological specimens, together with prominent vessels lined by plump endothelial cells. Increasing evidence suggests that this condition is neither necessarily acral, pseudolymphomatous, nor angiokeratomatous. It may not always be a pediatric disease. Therefore, the correctness of its nomenclature has been questioned. Herein, we report threecases whose clinical and histological features were consistent with the diagnosis of APACHE. To our knowledge, this is the first report of APACHE from Southeast Asia. We also discuss why we believe "APACHE" to be a misnomer and support "papular angiolymphoid hyperplasia" as a more accurate and encompassing term. In addition, we illustrate a case with significant overlapping features with lymphoplasmacytic plaque in children, suggesting that both entities may exist on a clinical andhistological spectrum.


Assuntos
Angioceratoma/patologia , Hiperplasia Angiolinfoide com Eosinofilia/patologia , Pseudolinfoma/patologia , Neoplasias Cutâneas/patologia , Criança , Feminino , Humanos , Masculino , Singapura , Dermatopatias/patologia , Terminologia como Assunto , Adulto Jovem
4.
Phys Rev Lett ; 108(25): 255008, 2012 Jun 22.
Artigo em Inglês | MEDLINE | ID: mdl-23004613

RESUMO

Field reversed configurations (FRCs) with high confinement are obtained in the C-2 device by combining plasma gun edge biasing and neutral beam injection. The plasma gun creates an inward radial electric field that counters the usual FRC spin-up. The n = 2 rotational instability is stabilized without applying quadrupole magnetic fields. The FRCs are nearly axisymmetric, which enables fast ion confinement. The plasma gun also produces E × B shear in the FRC edge layer, which may explain the observed improved particle transport. The FRC confinement times are improved by factors 2 to 4, and the plasma lifetimes are extended from 1 to up to 4 ms.

5.
J Environ Sci (China) ; 24(7): 1234-9, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-23513444

RESUMO

The decomposition of trifluoromethane (CHF3) was carried out using non-thermal plasma generated in a dielectric barrier discharge (DBD) reactor. The effects of reactor temperature, electric power, initial concentration and oxygen content were examined. The DBD reactor was able to completely destroy CHF3 with alumina beads as a packing material. The decomposition efficiency increased with increasing electric power and reactor temperature. The destruction of CHF3 gradually increased with the addition of O2 up to 2%, but further increase in the oxygen content led to a decrease in the decomposition efficiency. The degradation pathways were explained with the identified by-products. The main by-products from CHF3 were found to be COF2, CF4, CO2 and CO although the COF2 and CF4 disappeared when the plasma were combined with alumina catalyst.


Assuntos
Poluentes Atmosféricos/química , Clorofluorcarbonetos de Metano/química , Eletrólise , Óxido de Alumínio , Dióxido de Carbono/análise , Monóxido de Carbono/análise , Oxigênio/química , Espectroscopia de Infravermelho com Transformada de Fourier , Zircônio
6.
East Asian Arch Psychiatry ; 32(2): 34-38, 2022 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-35732478

RESUMO

OBJECTIVES: To compare the incidence of upper respiratory tract infection (URTI) between inpatients at the Institute of Mental Health in Singapore and the general population over 8 years to determine the effectiveness of our infection control strategies. METHODS: Data for cases of influenza and URTI at our institute between January 2012 and December 2019 were collected. National data were derived from weekly infectious disease bulletins that report daily averages of people attending polyclinics/surgeries with influenza and URTI. Interrupted time series analyses were used to determine the impact of infection prevention and control strategies on incidence. RESULTS: Over the 8 years, there were 1607 cases of URTI involving 182 clusters, equal to 3.16 cases per 10 000 patient-bed-days. 965 (60%) cases and 95 (52%) clusters occurred in long-stay wards, whereas 642 (40%) cases and 87 (48%) clusters occurred in acute wards. The median cluster size was 12 in the long-stay wards and 7 in the acute wards (p < 0.0001). The spikes in cases in June and December may be attributed to the increased staff and visitor mobility during school vacations in June and December. Strategies implemented during the study period did not significantly reduce the incidence of URTI. Previous strategies implemented in 2005 to meet accreditation standards are more likely to be contributors. CONCLUSION: Infection control strategies of our institute appear to be effective, because the incidence of URTI was lower in our institute than in the community. The similar incidence of URTI in acute and long-stay wards indicates that service-user turnover is not a contributor. Rather, staff and visitors are more likely to be the vector. The larger clusters in long-stay wards indicates a greater risk of transmission in such settings. Increased activity in our institute during school vacations may be associated with an increase in cases in June and December. It is difficult to determine if strategies implemented during the study period successfully reduce the incidence of URTI.


Assuntos
Influenza Humana , Infecções Respiratórias , Humanos , Incidência , Infecções Respiratórias/epidemiologia , Infecções Respiratórias/prevenção & controle , Singapura/epidemiologia
7.
Rev Sci Instrum ; 92(5): 053515, 2021 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-34243321

RESUMO

In this study, a newly developed correction method with external magnetic measurements for the magnetohydrodynamics (MHD) simulation of the collisional merging formation of a field-reversed configuration (FRC) realized the estimation of the internal structure of the FRCs without invasive internal measurements. In the collisional merging formation of FRCs, an FRC is formed via merging of two initial FRC-like plasmoids at supersonic/Alfvénic velocity. An invasive diagnostic may also interfere with the collisional merging formation process. A two-dimensional resistive MHD simulation was conducted to evaluate the global behavior and internal structure of FRCs in the collisional merging formation process without invasive measurements. This code simulated the initial formation and collisional merging processes of FRCs including discharge circuits. However, the translation velocity and the pressure of initial FRCs did not simultaneously agree with the experimental values because the magnetic pressure gradient in each formation region could not be reproduced without the artificial adjustment of the initial condition. The experimentally measured current distribution was given as the initial condition of the circuit calculation in the developed correction method. The initial FRCs were successfully translated at the translation velocity and plasma pressure in the corrected simulation, both of which were equivalent to the experiments. The properties of the merged FRCs in the experiments such as volume, total temperature, and average electron density were reproduced in the corrected simulation. The detailed radial profile of the internal magnetic field of the FRC was also measured and found to agree very well with the simulation results.

8.
Phys Rev Lett ; 105(4): 045003, 2010 Jul 23.
Artigo em Inglês | MEDLINE | ID: mdl-20867853

RESUMO

A hot stable field-reversed configuration (FRC) has been produced in the C-2 experiment by colliding and merging two high-ß plasmoids preformed by the dynamic version of field-reversed θ-pinch technology. The merging process exhibits the highest poloidal flux amplification obtained in a magnetic confinement system (over tenfold increase). Most of the kinetic energy is converted into thermal energy with total temperature (T{i}+T{e}) exceeding 0.5 keV. The final FRC state exhibits a record FRC lifetime with flux confinement approaching classical values. These findings should have significant implications for fusion research and the physics of magnetic reconnection.

10.
Int J Tuberc Lung Dis ; 23(4): 507-513, 2019 04 01.
Artigo em Inglês | MEDLINE | ID: mdl-31064631

RESUMO

SETTING The prevalence of diabetes mellitus (DM) worldwide is increasing markedly, and many countries with rising rates also have a high incidence rate of tuberculosis (TB). OBJECTIVE To investigate the relationships of fasting serum glucose (FSG) and DM with TB incidence, recurrence and mortality risk in a prospective cohort study in South Korea. DESIGN Our study comprised 1 267 564 Koreans who received health insurance from the National Health Insurance System, had an initial medical evaluation between 1997 and 2000 and were prospectively followed biennially. RESULTS Participants with DM had a higher risk for incident TB (hazard ratio [HR] 1.81, 95%CI 1.71-1.91 in males, HR 1.33; 95%CI 1.20-1.47 in females) than those without DM. There was a strong positive trend for TB risk with rising FSG among males. The risk for recurrent TB among those with previous TB was significantly higher in males (HR 1.58, 95%CI 1.43-1.75) and in females with DM (HR 1.38, 95%CI 1.08-1.76). The increased risk of death from TB during follow-up was also significant in men (HR 1.91, 95%CI 1.87-1.95) and in women (HR 1.71, 95%CI 1.65-1.77). CONCLUSIONS A diagnosis of DM is a risk factor for TB, TB recurrence and death from TB. Screening for TB should be considered among people living with DM in Korea, particularly those with severe DM. .


Assuntos
Diabetes Mellitus/epidemiologia , Programas de Rastreamento/métodos , Tuberculose/epidemiologia , Adulto , Idoso , Glicemia/análise , Estudos de Coortes , Diabetes Mellitus/diagnóstico , Feminino , Humanos , Incidência , Masculino , Pessoa de Meia-Idade , Programas Nacionais de Saúde , Estudos Prospectivos , Recidiva , República da Coreia/epidemiologia , Fatores de Risco , Tuberculose/diagnóstico
11.
J Phys Chem A ; 112(29): 6586-91, 2008 Jul 24.
Artigo em Inglês | MEDLINE | ID: mdl-18582026

RESUMO

This study investigated the decomposition of hydrofluorocarbons (HFCs) having high global warming potentials by using a dielectric-packed-bed nonthermal plasma reactor with barium titanate beads as the packing material. The target HFCs were 1,1,1,2-tetrafluoroethane (HFC-134a) and 1,1-difluoroethene (HFC-132a). The effects of several parameters such as reaction temperature, oxygen content, and initial concentration on the HFC decomposition efficiency were evaluated. There was essentially no temperature dependence of the HFC decomposition efficiency in the range 150-250 degrees C. The optimum oxygen content for HFC decomposition was found to be about 0.5 vol %. Variations in the initial concentration did not affect the decomposition efficiency. The decomposition products were analyzed, and some decomposition pathways were elucidated. The energy requirements for the decomposition of HFC-134a and HFC-132a were found to be 0.038 and 0.062 mol MJ-1, respectively, based on the initial concentrations of 200 and 120 ppm (parts per million, volumetric).

12.
Nat Commun ; 9(1): 691, 2018 02 15.
Artigo em Inglês | MEDLINE | ID: mdl-29449547

RESUMO

Active control of field reversed configuration (FRC) devices requires a method to determine the flux surface geometry and dynamic properties of the plasma during both transient and steady-state conditions. The current tomography (CT) method uses Bayesian inference to determine the plasma current density distribution using both the information from magnetic measurements and a physics model in the prior. Here we show that, from the inferred current sources, the FRC topology and its axial stability properties are readily obtained. When Gaussian process priors are used and the forward model is linear, the CT solution involves non-iterative matrix operations and is then ideally suited for deterministic real-time applications. Because no equilibrium assumptions are used in this case, inference of plasma topology and dynamics up to Alfvenic frequencies then becomes possible. Inference results for the C-2U device exhibit self-consistency of motions and forces during Alfvenic transients, as well as good agreement with plasma imaging diagnostics.

13.
Rev Sci Instrum ; 89(10): 10J114, 2018 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-30399830

RESUMO

Field-reversed configuration (FRC) Amplification via Translation-Collisional Merging (FAT-CM) experiments have recently commenced to study physics phenomena of colliding and merged FRC plasma states. Two independently formed FRCs are translated into the confinement region of the FAT-CM device, collided near the mid-plane of the device with a relative speed of up to ∼400 km/s, and a final merged FRC plasma state is achieved. To measure internal magnetic field profiles of the translated and merged FRC plasmas as well as to understand its collisional-merging process, an internal magnetic probe array, developed by TAE Technologies, has been installed in the mid-plane of the FAT-CM device. Initial magnetic field measurements indicate that both the translated and the merged FRC plasma states exhibit a clear field-reversed structure, which is qualitatively in good agreement with 2D MHD simulation. It is found and verified that a sufficient mirror field in the confinement region is required for colliding FRCs to be fully merged into a single FRC plasma state.

15.
Int J Gynaecol Obstet ; 98(2): 120-3, 2007 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-17585916

RESUMO

OBJECTIVE: To investigate whether the accuracy of vacuum cup placement can be improved by intrapartum ultrasound assessment of the fetal head position during the second stage of labor prior to vacuum extraction for prolonged second stage. METHODS: 50 women undergoing vacuum extraction for prolonged second stage were randomly allocated to either digital examination (n=25) or digital examination together with transabdominal intrapartum ultrasound (n=25) prior to vacuum extraction by the attending obstetrician. The distance between the centre of the chignon and the flexion point was then measured by a midwife immediately after delivery. The flexion point was defined as 6 cm posterior to the anterior fontanelle or 3 cm anterior to the posterior fontanelle. RESULTS: There were no statistically significant differences in the demographic data, duration of labor, incidence of induction/augmentation, and intrapartum complications between the two groups. The mean distance between the centre of the chignon and the flexion point was 2.1+/-1.3 cm in the group with digital examination and ultrasound assessment and 2.8+/-1.0 cm in the group with digital examination alone. The difference in the mean distance between the two groups was statistically significant (p=0.039). CONCLUSION: Intrapartum transabdominal ultrasound assessment of the fetal head position during the second stage of labor improves the accuracy of vacuum cup placement during vacuum extraction for prolonged second stage.


Assuntos
Apresentação no Trabalho de Parto , Complicações do Trabalho de Parto/diagnóstico por imagem , Vácuo-Extração/métodos , Adulto , Feminino , Humanos , Gravidez , Ultrassonografia
16.
Br J Radiol ; 90(1078): 20170052, 2017 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-28511550

RESUMO

Ovarian torsion is a surgical emergency characterized by a partial or complete rotation of the ovarian vascular pedicle, causing obstruction to venous outflow followed by arterial inflow. Clinically, ovarian torsion frequently mimics other causes of acute pelvic pain such as appendicitis, diverticulitis, renal colic etc. Ultrasonography is the first-line imaging modality of choice for evaluation of ovarian torsion. MRI is useful as a problem-solving tool in patients with equivocal or non-diagnostic ultrasonography studies. CT is ordinarily not utilized in a young female with suspected ovarian torsion due to the radiation dose. However, the significant expansion in use of CT imaging in emergency departments for female patients presenting with acute abdominal pain has increased the likelihood that ovarian torsion may be first seen on CT. In addition, a non-specific clinical presentation may lead to an initial imaging with CT rather than ultrasonography. Ultrasound features of the ovarian torsion are well known and sufficiently described across literature as compared with the CT scan findings. In view of the increasing usage of CT as the modality of choice in emergency settings, it is imperative for the radiologist to familiarize with the CT features of ovarian torsion. An early correct diagnosis by the radiologist in clinically unsuspected cases, facilitating a prompt surgery to restore the ovarian blood flow can prevent permanent irreversible damage. There is limited published data available on the CT features of ovarian torsion. This pictorial essay illustrates CT findings with histological correlation of surgically proven ovarian torsion in our institution. These patients were primarily investigated with CT scan for acute pelvic pain ascribed to non-gynaecological causes such as bowel or urinary tract lesions.


Assuntos
Doenças Ovarianas/diagnóstico por imagem , Doenças Ovarianas/cirurgia , Tomografia Computadorizada por Raios X , Anormalidade Torcional/diagnóstico por imagem , Anormalidade Torcional/cirurgia , Adolescente , Adulto , Feminino , Humanos
17.
Br J Pharmacol ; 149(6): 625-34, 2006 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-17016507

RESUMO

BACKGROUND AND PURPOSE: The aim of these experiments was to evaluate the significance of the chemical reaction between hydrogen sulphide (H2S) and nitric oxide (NO) for the control of vascular tone. EXPERIMENTAL APPROACH: The effect of sodium hydrosulphide (NaHS; H2S donor) and a range of NO donors, such as sodium nitroprusside (SNP), either alone or together, was determined using phenylephrine (PE)-precontracted rat aortic rings and on the blood pressure of anaesthetised rats. KEY RESULTS: Mixing NaHS with NO donors inhibited the vasorelaxant effect of NO both in vitro and in vivo. Low concentrations of NaHS or H2S gas in solution reversed the relaxant effect of acetylcholine (ACh, 400 nM) and histamine (100 microM) but not isoprenaline (400 nM). The effect of NaHS on the ACh response was antagonized by CuSO(4) (200 nM) but was unaffected by glibenclamide (10 microM). In contrast, high concentrations of NaHS (200-1600 microM) relaxed aortic rings directly, an effect reduced by glibenclamide but unaffected by CuSO4. Intravenous infusion of a low concentration of NaHS (10 micromol kg(-1) min(-1)) into the anaesthetized rat significantly increased mean arterial blood pressure. L-NAME (25 mg kg(-1), i.v.) pretreatment reduced this effect. CONCLUSIONS AND IMPLICATIONS: These results suggest that H2S and NO react together to form a molecule (possibly a nitrosothiol) which exhibits little or no vasorelaxant activity either in vitro or in vivo. We propose that a crucial, and hitherto unappreciated, role of H2S in the vascular system is the regulation of the availability of NO.


Assuntos
Aorta/metabolismo , Sulfeto de Hidrogênio/metabolismo , Óxido Nítrico/metabolismo , Animais , Aorta/fisiologia , Pressão Sanguínea , Técnicas In Vitro , Masculino , Contração Muscular/efeitos dos fármacos , Doadores de Óxido Nítrico/farmacologia , Nitroprussiato/farmacologia , Ratos , Ratos Sprague-Dawley
18.
Int J Tuberc Lung Dis ; 20(5): 619-24, 2016 May.
Artigo em Inglês | MEDLINE | ID: mdl-27084815

RESUMO

BACKGROUND: Studies evaluating the role of transbronchial lung biopsy (TBLB) in diagnosing pulmonary tuberculosis (PTB) date back decades and have shaped current practice. However, with the recent advent of bronchoalveolar lavage (BAL) Xpert® MTB/RIF, it is time to re-evaluate the role of TBLB. OBJECTIVE: To assess the impact of BAL and TBLB with the addition of BAL Xpert on diagnostic PTB yields and time to treatment initiation in sputum-scarce or acid-fast bacilli (AFB) smear-negative PTB patients. METHODS: We retrospectively reviewed all sputum-scarce or AFB smear-negative patients who underwent both BAL and TBLB for suspected PTB between March 2011 and October 2013. Xpert was performed on all BAL specimens. RESULTS: Of 158 patients included in our analysis, 44 were culture-proven PTB. Ninety-four per cent of the patients had AFB smear-negative BAL samples. The sensitivity and specificity of Xpert in AFB smear-negative BAL samples were respectively 60% and 98%. The addition of BAL Xpert expedited the institution of PTB treatment while having diagnostic yields comparable to those of conventional BAL with TBLB. CONCLUSIONS: The use of BAL Xpert may obviate the need for TBLB in increasing the diagnostic yield of PTB in sputum-scarce or AFB smear-negative patients.


Assuntos
Técnicas Bacteriológicas , Líquido da Lavagem Broncoalveolar/microbiologia , DNA Bacteriano/genética , Farmacorresistência Bacteriana/genética , Pulmão/microbiologia , Técnicas de Diagnóstico Molecular , Mycobacterium tuberculosis/genética , Tuberculose Pulmonar/diagnóstico , Adulto , Idoso , Antibióticos Antituberculose/uso terapêutico , Biópsia , DNA Bacteriano/isolamento & purificação , Feminino , Humanos , Pulmão/efeitos dos fármacos , Pulmão/patologia , Masculino , Pessoa de Meia-Idade , Mycobacterium tuberculosis/efeitos dos fármacos , Mycobacterium tuberculosis/isolamento & purificação , Valor Preditivo dos Testes , Reprodutibilidade dos Testes , Estudos Retrospectivos , Rifampina/uso terapêutico , Escarro/microbiologia , Tuberculose Pulmonar/tratamento farmacológico , Tuberculose Pulmonar/microbiologia , Tuberculose Pulmonar/patologia
19.
J Mol Biol ; 276(5): 939-54, 1998 Mar 13.
Artigo em Inglês | MEDLINE | ID: mdl-9566198

RESUMO

Two new NMR experiments are presented for measuring side-chain dynamics in proteins. The first method, requiring 15N, 13C, approximately 50% 2H-labeled protein, measures 2H T1 and T1p spin relaxation times at side-chain positions. A second experiment permits the straightforward measurement of 13C-1H dipole-dipole cross-correlation relaxation rates at 13C beta positions in 15N, 13C-labeled molecules. An excellent correlation is observed between order parameters, describing the amplitude of motion at these sites, obtained on the basis of 2H relaxation and dipole-dipole cross-correlation relaxation rates. Together these experiments provide a powerful approach for selecting appropriate motional models. The methods are applied to study the side-chain motional properties of the N-terminal SH3 domain from the signaling protein drk.


Assuntos
Proteínas de Drosophila , Proteínas de Insetos/química , Espectroscopia de Ressonância Magnética/métodos , Animais , Isótopos de Carbono , Deutério , Termodinâmica , Domínios de Homologia de src
20.
J Mol Biol ; 303(3): 359-70, 2000 Oct 27.
Artigo em Inglês | MEDLINE | ID: mdl-11031113

RESUMO

PDZ domains are modular protein units that play important roles in organizing signal transduction complexes. PDZ domains mediate interactions with both C-terminal peptide ligands and other PDZ domains. Here, we used PDZ domains from neuronal nitric oxide synthase (nNOS) and postsynaptic density protein-95 (PSD-95) to explore the mechanism for PDZ-dimer formation. The nNOS PDZ domain terminates with a approximately 30 residue amino acid beta-finger peptide that is shown to be required for nNOS/PSD-95 PDZ dimer formation. In addition, formation of the PDZ dimer requires this beta-finger peptide to be physically anchored to the main body of the canonical nNOS PDZ domain. A buried salt bridge between the beta-finger and the PDZ domain induces and stabilizes the beta-hairpin structure of the nNOS PDZ domain. In apo-nNOS, the beta-finger peptide is partially flexible and adopts a transient beta-strand like structure that is stabilized upon PDZ dimer formation. The flexibility of the NOS PDZ beta-finger is likely to play a critical role in supporting the formation of nNOS/PSD-95 complex. The experimental data also suggest that nNOS PDZ and the second PDZ domain of PSD-95 form a "head-to-tail" dimer similar to the nNOS/syntrophin complex characterized by X-ray crystallography.


Assuntos
Proteínas do Tecido Nervoso/química , Proteínas do Tecido Nervoso/metabolismo , Óxido Nítrico Sintase/química , Óxido Nítrico Sintase/metabolismo , Motivos de Aminoácidos , Sequência de Aminoácidos , Sítios de Ligação , Dicroísmo Circular , Dimerização , Modelos Moleculares , Dados de Sequência Molecular , Mutação/genética , Proteínas do Tecido Nervoso/genética , Óxido Nítrico Sintase/genética , Óxido Nítrico Sintase Tipo I , Ressonância Magnética Nuclear Biomolecular , Maleabilidade , Ligação Proteica , Estrutura Secundária de Proteína , Estrutura Terciária de Proteína , Proteínas Recombinantes , Eletricidade Estática , Especificidade por Substrato , Ressonância de Plasmônio de Superfície
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA