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1.
Prehosp Emerg Care ; : 1-10, 2021 Jul 12.
Artigo em Inglês | MEDLINE | ID: mdl-34115573

RESUMO

Background: In response to the COVID-19 pandemic, Emergency Medical Services (EMS) systems have received guidelines as part of coordinated response efforts aimed at mitigating exposures and ensuring occupational wellbeing, including recommendations of Personal Protective Equipment (PPE) utilization, and modifications of Emergency Medical Dispatch (EMD) caller queries. The aim of the study was to estimate the sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of an EMD telephone screening process for the identification of hospital diagnosed COVID-19 positive patients. Methods: A retrospective cohort study was conducted of adult EMS encounters presenting to hospitals within a large health system from March 16-June 30, 2020. EMD telephone screening status was defined as either "positive" or "negative" and was collected from prehospital medical records. COVID-19 positive patients were confirmed via hospital laboratory diagnosis and were matched to their prehospital medical record data. Patient demographics and EMS encounter level data, such as Dispatch Code and Priority level, were also collected. Estimations of sensitivity, specificity, PPV and NPV were made. Emergency telephone screening status was stratified by COVID-19 diagnosis to describe discordant pairs. Results: Of the 3,443 total encounters screened, there were 652 patients who were subsequently COVID-19 positive per hospital diagnosis (18.9%). Approximately 5.0% of all encounters did not screen positive on EMD screening but were later COVID-19 positive. Conversely, 44.2% of encounters screened positive for COVID-19, but were subsequently negative. Sensitivity of the EMD telephonic screening was estimated as 75.0% (95% CI 71.7%, 78.3%) and specificity was 45.5% (95% CI 43.7%, 47.4%). The PPV was 24.3% (95% CI 22.5%, 26.0%), and NPV 88.6% (95% CI 87.0%, 90.3%). Conclusions: The sensitivity of the EMD telephonic screening process was moderately able to identify COVID-19 positive patients. There is a need to reevaluate and revise guidelines and recommendations, specifically modified caller queries, as part of ongoing pandemic emergency response efforts in order to reduce transmissions and maximize patient and provider safety.

2.
Am J Emerg Med ; 36(6): 1022-1026, 2018 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-29426799

RESUMO

BACKGROUND: Recently a multispecialty, multinational task force convened to redefine the criteria for organ dysfunction, sepsis, severe sepsis, and septic shock. The study recommended the quick sequential organ failure assessment (qSOFA) score to identify sepsis patients. The qSOFA is felt to be the initial screen to prompt a more in-depth sepsis workup. This may be particularly true in resource-limited environments such as the prehospital arena. OBJECTIVES: The goal of this study was to identify whether emergency medical services (EMS) patients who met all three qSOFA criteria correlated with an emergency department (ED) identification of sepsis. METHODS: This was a retrospective chart review of adult patients≥18years of age, meeting qSOFA criteria and presenting to the emergency department between 1/01/2014 and 6/30/2016. Subjects were identified through an electronic query of the EMS record repository. RESULTS: 72 subjects were included in the final analysis. Subjects in the septic group tended to be older with a mean age of 72years vs 64years. There was no observed discrepancy relating to gender. 48 of the subjects (67%) were identified as septic and 24 (33%) were identified as non-septic after review of the ED chart. This yielded a positive predictive value of the prehospital qSOFA as 66.67% (95% CI 55.8-77.6). CONCLUSIONS: EMS patients with positive qSOFA screens were more likely to be septic upon disposition to the ED.


Assuntos
Serviços Médicos de Emergência/métodos , Medição de Risco/métodos , Choque Séptico/diagnóstico , Idoso , Feminino , Mortalidade Hospitalar/tendências , Humanos , Masculino , Pessoa de Meia-Idade , Escores de Disfunção Orgânica , Curva ROC , Estudos Retrospectivos , Choque Séptico/mortalidade , Taxa de Sobrevida/tendências , Estados Unidos/epidemiologia
3.
Acc Chem Res ; 45(11): 1992-2001, 2012 Nov 20.
Artigo em Inglês | MEDLINE | ID: mdl-22775295

RESUMO

In contrast to the detailed understanding of inorganic materials, researchers lack a comprehensive view of how the properties of bulk organic materials arise from their individual components. For conjugated polymers to eventually serve as low cost semiconductor layers in electronic devices, researchers need to better understand their functionality. For organics, traditional materials science measurements tend to destroy the species of interest, especially at low concentrations. However, fluorescence continues to be a remarkably flexible, relatively noninvasive tool for probing the properties of individual molecules and allows researchers to carry out a broad range of experiments based on a relatively simple concept. In addition, the sensitivity of single-molecule spectroscopy allows researchers to see the properties of an individual component that would be masked in the bulk phase. In this Account, we examine several photophysical properties of different conjugated polymers using single-molecule spectroscopy. In these experiments, we probed the relationship between the conformation of single conjugated polymer chains and the distance scale and efficiency of energy transfer within the polymer. Recent studies used polarization anisotropy measurements on single polymer chains to study chain folding following spin-casting from solution. This Account summarizes the effects of monomer regioregularity and backbone rigidity, by comparing a regiorandom phenylene vinylene (MEH-PPV) with both a regiorandom and regioregular thiophene (P3HT). Synthesis of novel polymers allowed us to explore the role of different conformation-directing inclusions in a PPV backbone. We showed that these inclusions control the conformation of individual chains and that molecular dynamics can predict these structural effects. In situ solvent vapor annealing studies explored the dynamics of polymer chains as well as the effect of solvent evaporation on the structural equilibrium of the polymer. We observed that a slower rate of solvent evaporation results in a narrow population of highly ordered polymer chains. These highly ordered single chains serve as a model system to probe the effect of conformation on energy transfer following excitation in single MEH-PPV polymer chains in two distinct experiments. In the first, we correlated the anisotropy of the fluorescence emission of individual chains with the anisotropy of their fluorescence excitation. Using this data, we derived a model for energy transfer in a conjugated polymer, simulating chromophores along a chain, coupled via Förster energy transfer. In the second experiment, super-resolution measurements demonstrated the ability of single-molecule spectroscopy to directly visualize energy transfer along a polymer chain embedded in a model device environment. A capacitive device allowed for controlled localization of hole polarons onto the polymer chain. These positive charges subsequently quenched local excitations, providing insight into the range of energy transfer in these single polymer molecules. As researchers continue to characterize conjugated polymer films and develop methods for creating multichain systems, single-molecule techniques will provide a greater understanding of how polymer morphology influences interchain interactions and will lead to a richer description of the electronic properties of bulk conjugated polymer films.

4.
Resusc Plus ; 14: 100397, 2023 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-37252026

RESUMO

Background: The objective was to describe emergency medical services (EMS) protocol variability in transport expectations for out-of-hospital cardiac arrest (OHCA) patients and the involvement of online medical control for on-scene termination of resuscitation in the United States. Whether other aspects of OHCA care were mentioned, including the definition of a "pediatric" patient, and use of end-tidal carbon dioxide monitoring, mechanical chest compression devices (MCCDs), and extracorporeal membrane oxygenation (ECMO), were also described. Methods and Results: Review of EMS protocols publicly accessible from https://www.emsprotocols.org and through searches on the internet when protocols were unavailable on the website from June 2021 to January 2022. Frequencies and proportions were used to describe outcomes. Of 104 protocols reviewed, 51.9% state to initiate transport after return of spontaneous circulation (ROSC), 26.0% do not specify when to initiate transport, and 6.7% state to transport after ≥20 minutes of on-scene cardiopulmonary resuscitation for adults. For pediatric patients, 38.5% of protocols do not specify when to initiate transport, 32.7% state to transport after ROSC, and 10.6% state to transport as soon as possible. Most protocols (42.3%) did not specify the age that defines "pediatric" in cardiac arrest. More than half (51.9%) of the protocols require online medical control for termination of resuscitation. Most protocols mention the use of end-tidal carbon dioxide monitoring (81.7%), 50.0% mention the use of MCCDs, and 4.8% mention ECMO for cardiac arrest. Conclusions: In the United States, EMS protocols for initiation of transport and termination of resuscitation for OHCA patients are highly variable.

5.
Resuscitation ; 188: 109833, 2023 07.
Artigo em Inglês | MEDLINE | ID: mdl-37178900

RESUMO

BACKGROUND: The Resuscitation Quality Improvement® (RQI®) HeartCode Complete® program is designed to enhance cardiopulmonary resuscitation (CPR) training by using real-time feedback manikins. Our objective was to assess the quality of CPR, such as chest compression rate, depth, and fraction, performed on out-of-hospital cardiac arrest (OHCA) patients among paramedics trained with the RQI® program vs. paramedics who were not. METHODS AND RESULTS: Adult OHCA cases from 2021 were analyzed; 353 OHCA cases were classified into one of three groups: 1) 0 RQI®-trained paramedics, 2) 1 RQI®-trained paramedic, and 3) 2-3 RQI®-trained paramedics. We reported the median of the average compression rate, depth, and fraction, as well as percent of compressions that were between 100 to 120/minute and percent of compressions that were 2.0 to 2.4 inches deep. Kruskal-Wallis Tests were used to assess differences in these metrics across the three groups of paramedics. Of 353 cases, the median of the average compression rate/minute among crews with 0, 1, and 2-3 RQI®-trained paramedics was 130, 125, and 125, respectively (p = 0.0032). Median percent of compressions between 100 to 120 compressions/minute was 10.3%, 19.7%, and 20.1% among crews with 0, 1, and 2-3 RQI®-trained paramedics, respectively (p = 0.0010). Median of the average compression depth was 1.7 inches across all three groups (p = 0.4881). Median compression fraction was 86.4%, 84.6%, and 85.5% among crews with 0, 1, and 2-3 RQI®-trained paramedics, respectively (p = 0.6371). CONCLUSIONS: RQI® training was associated with statistically significant improvement in chest compression rate, but not improved chest compression depth or fraction in OHCA.


Assuntos
Reanimação Cardiopulmonar , Serviços Médicos de Emergência , Parada Cardíaca Extra-Hospitalar , Adulto , Humanos , Reanimação Cardiopulmonar/métodos , Parada Cardíaca Extra-Hospitalar/terapia , Melhoria de Qualidade , Serviços Médicos de Emergência/métodos , Hospitais
6.
Nat Mater ; 10(12): 942-6, 2011 Oct 09.
Artigo em Inglês | MEDLINE | ID: mdl-21983890

RESUMO

Applications of conjugated polymers (CP) in organic electronic devices such as light-emitting diodes and solar cells depend critically on the nature of electronic energy transport in these materials. Single-molecule spectroscopy has revealed their fundamental properties with molecular detail, and recent reports suggest that energy transport in single CP chains can extend over extraordinarily long distances of up to 75 nm. An important question arises as to whether these characteristics are sustained when CP chains agglomerate into a neat solid. Here, we demonstrate that the electronic energy transport in aggregates composed of tens of polymer chains takes place on a similar distance scale as that in single chains. A recently developed molecular-level understanding of solvent vapour annealing has allowed us to develop a technique to control the CP agglomeration process. Aggregates with volumes of at least 45,000 nm(3) (molecular weight ≈ 21 MDa) maintain a highly ordered morphology and show pronounced fluorescence blinking behaviour, indicative of substantially long-range energy transport. Our findings provide a new lens through which the ordering of single CP chains and the evolution of their morphological and optoelectronic properties can be observed, which will ultimately enable the rational design of improved CP-based devices.

7.
Proc Natl Acad Sci U S A ; 106(5): 1342-6, 2009 Feb 03.
Artigo em Inglês | MEDLINE | ID: mdl-19171882

RESUMO

The injection of positive charge carriers (holes) into a single conjugated polymer chain was observed to be light-assisted. This effect may underlie critical, poorly understood organic electronic device phenomena such as the build-up of functional deeply trapped charge layers in polymer light emitting diodes. The charging/discharging dynamics were investigated indirectly by a variety of single molecule electro-optical spectroscopic techniques, including an "image-capture" approach.

8.
West J Emerg Med ; 23(3): 396-407, 2022 May 05.
Artigo em Inglês | MEDLINE | ID: mdl-35679488

RESUMO

INTRODUCTION: The use of personal protective equipment (PPE) is a salient component of reducing occupational risk in many fields. Emergency medical services (EMS) personnel use PPE to reduce risk of exposure and defend against various pathogens they come in contact with while providing patient care. Currently, the understanding of factors that predict the use of PPE by an EMS responder during a pandemic is limited. In this study our objective was to identify factors that influenced PPE use by EMS responders during the coronavirus disease 2019 (COVID-19) pandemic, which may guide future planning for responders in similar austere or personal risk situations. METHODS: We conducted a retrospective chart review among all EMS encounters across an EMS agency affiliated with a large New York health system from March 16-June 30, 2020. All adult, emergency encounters with available prehospital record data were analyzed. We assessed patient- and EMS encounter-level data as possible factors that influence PPE utilization. The use of PPE was defined and guided by the literature as being either full or partial PPE, or "not documented." We used multinomial logistic regression to identify factors that influence PPE use among EMS responders. RESULTS: We identified 28,693 eligible EMS encounters during the study period; 54.2% of patients were male, the median patient age was 58 years, and 66.9% of patients had at least one chronic medical condition. The use of PPE was documented in 92.8% of encounters, with full PPE used in 17.8% of these encounters. Full PPE utilization, relative to partial, was most strongly influenced by dispatch codes indicative of "breathing problems" (odds ratio [OR] 4.89; 95% confidence interval [CI]: 4.40, 5.46) and "cardiac/respiratory arrest" (OR 3.82; 95% CI: 2.99, 4.88), in addition to a patient's positive screening for COVID-19 on 9-1-1 dispatch (OR 3.97; 95% CI: 3.66, 4.32). CONCLUSION: Emergency medical services responders more frequently used full PPE for calls with dispatch codes indicative of respiratory distress or cardiac arrest. Understanding factors that influence PPE use among EMS personnel, particularly during times of public health emergencies, is essential to mitigate exposure and ensure the safety of frontline responders.


Assuntos
COVID-19 , Serviços Médicos de Emergência , Adulto , COVID-19/prevenção & controle , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Pandemias/prevenção & controle , Equipamento de Proteção Individual , Estudos Retrospectivos
9.
Emerg Med Int ; 2022: 3044891, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35273813

RESUMO

Background: As integrated health systems become more common, interfacility patient transfers will increase and air transport programs will be prioritized. Understanding characteristics of patients triaged to air medical transport will assist with resource allocation and needs assessment. The objective of this study was to investigate the demographics and clinical characteristics of patients that presented to the emergency department (ED) and subsequently required emergent air medical interfacility transport. Methods: This was a retrospective, multicenter study conducted at eight hospitals within Northwell Health, the largest academic health system in New York state. The study was conducted between December 1, 2014, and July 31, 2020, and included patients who presented to an ED and subsequently required emergent air medical interfacility transport. Results: Overall, the median age was 37 years (IQR 4-66), and 231 (54%) subjects were males. The majority of subjects (59%) had no reported comorbidities, arrived by ambulance (52%), and were emergency severity index triage 2 (48%). Frequent indications for transfer were nontraumatic neurologic (37%), pulmonary or respiratory (13%), trauma (12%), and cardiovascular (12%). Most patients were not ventilated before transport (71%). The median time to call for transport at the sending institution was 2:42 hours (IQR 1:14-6:54), and the median length of stay was 4:12 (IQR 2:31-8:48). Most patients were subsequently admitted (96%) at the receiving institution to an intensive care unit (72%). Conclusions: This study describes patients' demographic and clinical characteristics who required emergent air medical transport. Helicopter transport is costly, and data from these patients may further help our understanding of who is transported by air and how important air transport is to the health system.

10.
J Am Chem Soc ; 133(31): 11994-2000, 2011 Aug 10.
Artigo em Inglês | MEDLINE | ID: mdl-21702448

RESUMO

A new phenomenon is presented in which electrogenerated chemiluminescence (ECL) is generated and propagates laterally as self-reinforcing waves as a result of the oxidation of a poly(9,9-dioctylfluorene-co-benzothiadiazole) thin film. In an ordered array of Au electrode posts that act as effective ECL nucleation sites, soliton-like waves were observed to expand from each site and annihilate upon collision with each other. Simulations of the ECL response supported the experimental observations that the ECL waves propagate at a constant speed. A correlated diffusion mechanism involving the correlated motion of ions, injected holes, and solvent molecules is proposed to interpret the experimental data qualitatively. A rapid increase in the diffusion coefficient of these species in the polymer results in a sharp interface between non-oxidized and oxidized polymer phases wherein the electrochemical (EC) oxidation and mass transport of all pertinent species take place. EC oxidation of conjugated polymers of this type has important implications for the understanding of these materials and their modes of operation in EC conjugated polymer devices.

11.
J Am Chem Soc ; 133(26): 10155-60, 2011 Jul 06.
Artigo em Inglês | MEDLINE | ID: mdl-21612291

RESUMO

The Horner method was used to synthesize random copolymers of poly(2-methoxy-5-(2'-ethylhexyloxy)-p-phenylene vinylene) (MEH-PPV) that incorporated different backbone-directing monomers. Single-molecule polarization absorption studies of these new polymers demonstrate that defects that preserve the linear backbone of PPV-type polymers assume the highly anisotropic configurations found in defect-free MEH-PPV. Rigid defects that are bent lower the anisotropy of the single chain, and saturated defects that provide rotational freedom for the chain backbone allow for a wide variety of possible configurations. Molecular dynamics simulations of model defect PPV oligomers in solution demonstrate that defect-free and linearly defected oligomers remain extended while the bent and saturated defects tend toward more folded, compact structures.

12.
Phys Rev Lett ; 106(22): 226403, 2011 Jun 03.
Artigo em Inglês | MEDLINE | ID: mdl-21702620

RESUMO

We use first-principles computational methods to examine hole trapping in organic molecular crystals. We present a computational scheme based on the tuning of the fraction of exact exchange in hybrid density functional theory to eliminate the many-electron self-interaction error. With small organic molecules, we show that this scheme gives accurate descriptions of ionization and dimer dissociation. We demonstrate that the excess hole in perfect molecular crystals forms self-trapped molecular polarons. The predicted absolute ionization potentials of both localized and delocalized holes are consistent with experimental values.

14.
Macromol Rapid Commun ; 32(7): 598-603, 2011 Apr 04.
Artigo em Inglês | MEDLINE | ID: mdl-21438059

RESUMO

We recently reported the discovery of soliton-like electrogenerated chemiluminescence (ECL) waves from pure conjugated polymer films and gold-nanoparticles-doped polymer films. In addition to a more detailed study of these polymer systems by changing the film thickness and the distribution of local leaks, we also apply the ECL wave phenomenon to polymer blends of conjugated and nonconjugated polymers. Poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT) is used as the active material that is oxidized and produces ECL with the presence of a co-reactant, tri-n-propylamine (TPA). Several factors such as film thickness, artificial leaks, and solubility of doped polymers are examined for their effects on the ECL behavior. When polystyrene (PS), less soluble in the electrolyte, is blended with F8BT, dotted ECL signals are observed and transported as waves. When poly(methyl methacrylate) (PMMA), more soluble in the electrolyte, is blended with F8BT, PMMA serves as local scratches and ECL waves are triggered simultaneously from the whole film.


Assuntos
Fluorenos/química , Luminescência , Polímeros/química , Eletricidade , Polimetil Metacrilato/química , Poliestirenos/química , Propilaminas/química
15.
J Emerg Med ; 40(1): 7-13, 2011 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-18829206

RESUMO

Visualization of the vocal cords is paramount during orotracheal intubations. We employed a novel patient position in this derivation study. The Alexandrou Angle of Intubation (AAI) position is defined as a 20°-30° incline where the supine patient's head is elevated in relation to the body and legs. Our study participants were blinded to the goals of the research as well as our novel technique. Using intubation manikins, our participants ranked their preference for visualizing the vocal cords between the Flat, Trendelenburg, and AAI positions. A majority (58.8%) of our study participants preferred the AAI for visualizing the vocal cords over the other two positions. Future studies will reveal whether AAI will play a significant role in emergent airway management.


Assuntos
Intubação Intratraqueal/métodos , Serviços Médicos de Emergência , Humanos , Manequins , Posicionamento do Paciente , Preferência do Paciente
16.
Biophys J ; 99(10): 3454-62, 2010 Nov 17.
Artigo em Inglês | MEDLINE | ID: mdl-21081095

RESUMO

We report a comparative study in which a single-molecule fluorescence resonance energy transfer approach was used to examine how the binding of two families of HIV-1 viral proteins to viral RNA hairpins locally changes the RNA secondary structures. The single-molecule fluorescence resonance energy transfer results indicate that the zinc finger protein (nucleocapsid) locally melts the TAR RNA and RRE-IIB RNA hairpins, whereas arginine-rich motif proteins (Tat and Rev) may strengthen the hairpin structures through specific binding interactions. Competition experiments show that Tat and Rev can effectively inhibit the nucleocapsid-chaperoned annealing of complementary DNA oligonucleotides to the TAR and RRE-IIB RNA hairpins, respectively. The competition binding data presented here suggest that the specific nucleic acid binding interactions of Tat and Rev can effectively compete with the general nucleic acid binding/chaperone functions of the nucleocapsid protein, and thus may in principle help regulate critical events during the HIV life cycle.


Assuntos
Arginina/metabolismo , HIV-1/metabolismo , Proteínas do Nucleocapsídeo/metabolismo , RNA Viral/metabolismo , Dedos de Zinco , Produtos do Gene rev do Vírus da Imunodeficiência Humana/metabolismo , Produtos do Gene tat do Vírus da Imunodeficiência Humana/metabolismo , Sequência de Aminoácidos , Sequência de Bases , Ensaio de Desvio de Mobilidade Eletroforética , Transferência Ressonante de Energia de Fluorescência , Repetição Terminal Longa de HIV/genética , Cinética , Dados de Sequência Molecular , Conformação de Ácido Nucleico , Ligação Proteica , RNA Viral/química , RNA Viral/genética , Elementos de Resposta/genética , Produtos do Gene rev do Vírus da Imunodeficiência Humana/química , Produtos do Gene tat do Vírus da Imunodeficiência Humana/química
17.
Hosp Pract (1995) ; 48(3): 137-145, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32326780

RESUMO

BACKGROUND: There are known demographic and clinical patterns related to burn injuries and care associated with national and global geography. Still, limited data sources exist to facilitate the study of trends in the regionalization of burn care. OBJECTIVES: The current study aims to investigate the demographics and clinical characteristics of patients that presented to the Emergency Department (ED) and were subsequently admitted for treatment to the inpatient unit of a regional burn center. METHODS: This retrospective, single-center study was conducted between 1 February 2018 and 31 July 2019, of ED patients who presented with a burn injury and were subsequently admitted to the hospital. RESULTS: We identified 329 patients with burn injuries requiring hospitalization. The median age was 22 years [IQR 2-53], and 195 (59%) subjects were males. Monthly and seasonal variations in admissions were identified. The majority of burns occurred at home (84%) and secondary to a scalding injury (59%). The lower extremity was the most common site of injury (29%). Most subjects received antibiotics (59%) and narcotic analgesia (56%) in the ED. The median hospital length of stay was four days [IQR 2-11]. Many subjects did not require surgical intervention (64%) and did not experience complications (79%). CONCLUSIONS: In this study, we describe the demographics and clinical characteristics of patients that presented to the ED and were subsequently admitted to a regional burn center. Analyzing the epidemiological information and clinical management of burns may better prepare healthcare providers to offer care to patients with burn injuries.


Assuntos
Unidades de Queimados/estatística & dados numéricos , Queimaduras/epidemiologia , Queimaduras/fisiopatologia , Serviço Hospitalar de Emergência/estatística & dados numéricos , Hospitalização/estatística & dados numéricos , Adolescente , Adulto , Analgésicos Opioides/administração & dosagem , Antibacterianos/administração & dosagem , Queimaduras/tratamento farmacológico , Criança , Pré-Escolar , Feminino , Humanos , Lactente , Tempo de Internação , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Fatores Socioeconômicos , Adulto Jovem
18.
J Am Chem Soc ; 131(42): 15534-43, 2009 Oct 28.
Artigo em Inglês | MEDLINE | ID: mdl-19919167

RESUMO

The human immunodeficiency virus type-1 (HIV-1) nucleocapsid (NC) protein is believed to be unique among the nucleic acid (NA) binding proteins encoded by this retrovirus in being highly multifunctional and relatively nonsequence-specific. Underlying many of NC's putative functions, including for example its chaperon-like activity for various steps of HIV-1 reverse transcription, is NC's ability to partially melt short double-stranded regions of structured NAs, which is essentially a consequence of NC's general binding preference for single-stranded bases. Herein we report a different, previously undiscovered, mode of NC/NA interaction, i.e., NC-induced sharp bending of short segments of fully duplexed DNA/DNA and DNA/RNA. We use single-molecule fluorescence resonance energy transfer (SM-FRET) in vitro to probe NC-induced NA bending and associated heterogeneous conformational dynamics for model NC/NA complexes. NC-induced NA bending may have important biological roles in the previously reported NC-mediated condensation of duplex proviral DNA in the HIV-1 life cycle.


Assuntos
DNA/química , HIV-1/química , Proteínas do Nucleocapsídeo/química , Sequência de Aminoácidos , HIV-1/genética , Dados de Sequência Molecular , Mutação , Proteínas do Nucleocapsídeo/genética
19.
J Am Chem Soc ; 131(40): 14166-7, 2009 Oct 14.
Artigo em Inglês | MEDLINE | ID: mdl-19807171

RESUMO

We report the discovery of soliton-like electrogenerated chemiluminescence (ECL) waves in the electrochemical oxidation of thin films (15-250 nm) of the semiconducting conjugated polymer poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT). The ECL "wave fronts" were visualized and imaged in space and time by optical emission microscopy and observed to freely propagate parallel to the plane of the electrode. The data reveal that the EC solitons are triggered by the flux of electrolytes into the polymer film at nanoscale "leaks" (or defects) and propagate by a highly nonlinear, positive-feedback kinetic mechanism involving EC oxidation, mass transport of electrolyte anions, and oxidation-induced swelling, all taking place within the conjugated polymer film. Several model systems with spatially distributed reaction "triggers" were studied to elucidate the mechanistic details of this complex oxidation process in polymer films.

20.
J Phys Chem A ; 113(16): 4739-45, 2009 Apr 23.
Artigo em Inglês | MEDLINE | ID: mdl-19260669

RESUMO

New insights on the molecular level details of the recently reported light-assisted injection of positive charge into single conjugated polymer chains are reported. Extensive new fluorescence-voltage single molecule spectroscopy (FV-SMS) measurements were performed on single chains of the archetypical conjugated polymer MEH-PPV embedded in a capacitor device to complement previous studies of the influence of the bias scan rate and optical excitation intensity. The use of a vacuum microscope allowed for the precise control of the device atmosphere, demonstrating the influence of triplet states in the MEH-PPV on the FV-SMS modulation. For identical device conditions, little variation was observed in the rate and yield of charging from molecule to molecule. Through the use of thicker supporting matrices and insulating polymer "blocking layers", it was determined that good electrical contact between the hole transport layers and the single molecules was necessary for charge injection. The results demonstrate the complexity of charge transfer processes at the interface of organic semiconductors and highlight the ability of single molecule methods to advance the understanding of such processes at the nanoscale.

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