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Understanding the Li-ions conduction network and transport dynamics in polymer electrolyte is crucial for developing reliable all-solid-state batteries. In this work, advanced nano- X-ray computed tomography combined with Raman spectroscopy and solid state nuclear magnetic resonance are used to multi-scale qualitatively and quantitatively reveal ion conduction network of poly(ethylene) oxide (PEO)-based electrolyte (from atomic, nano to macroscopic level). With the clear mapping of the microstructural heterogeneities of the polymer segments, aluminium-oxo molecular clusters (AlOC) are used to reconstruct a high-efficient conducting network with high available Li-ions (76.7%) and continuous amorphous domains via the strong supramolecular interactions. Such superionic PEO conductor (PEO-LiTFSI-AlOC) exhibites a molten-like Li-ion conduction behaviour among the whole temperature range and delivers an ionic conductivity of 1.87 × 10-4 S cm-1 at 35 °Ï¹. This further endows Li electrochemical plating/stripping stability under 50 µA cm-2 and 50 µAh cm-2 over 2000 h. The as-built Li|PEO-LiTFSI-AlOC|LiFePO4 full batteries show a high rate performance and a capacity retention more than 90% over 200 cycling at 250 µA cm-2, even enabling a high-loading LiFePO4 cathode of 16.8 mg cm-2 with a specific capacity of 150 mAh g-1 at 50 °Ï¹.
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Although metal-organic polyhedra (MOPs) expansion has been studied to date, it is still a rare occurrence for their porous intermolecular assembly for iodine capture. The major limitation is the lack of programmable and controllable methods for effectively constructing and utilizing the exterior cavities. Herein, the goal of programmable porous intermolecular assembly is realized in the first family of aluminum oxo polyhedrons (AlOPs) using ligands with directional H-bonding donor/acceptor pairs and auxiliary alcohols as structural regulation sites. The approach has the advantage of avoiding the use of expensive edge-directed ditopic and face-directed tritopic ligands in the general synthesis strategy of MOPs. Combining theoretical calculations and experiments, the intrinsic relationship is revealed between alcohol ligands and the growth mechanism of AlOPs. The maximum I2 uptake based on the mass gain during sorption corresponds to 2.35 g g-1, representing the highest reported I2 sorption by an MOP. In addition, it can be easily regenerated and maintained the iodine sorption capacity, revealing its further potential application. This method of constructing stable and programmable porous materials will provide a new way to solve problems such as radionuclide capture.
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Metal molecular rings are a class of compounds with aesthetically pleasing symmetry and fundamentally useful properties. The reported work generally focuses on the ring center cavity, and there is little known about those on the ring waist. Herein, we report the discovery of porous aluminum molecular rings and their performance and contribution to the cyanosilylation reaction. We develop a facile ligand induced aggregation and solvent regulation strategy towards AlOC-58NC and AlOC-59NT with high purity, high yield (75% and 70%, respectively) and gram-level scale-up. These molecular rings exhibit a "two-tier" pore feature involving the general central cavity and newly observed equatorial semi-open cavities. AlOC-59NT with two types of one-dimensional channels showed good catalytic activity. The interaction of the aluminum molecular ring catalyst with the substrate has been crystallographically characterized and theoretically confirmed, showing a ring adaptability process that involves the capture and binding of the substrate. This work provides new ideas for the assembly of porous metal molecular rings and to understand the overall reaction pathway involving aldehydes and is expected to inspire the design of low-cost catalysts through structural modifications.
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To create an artificial structure to remarkably surpass the sensitivity, selectivity and speed of the olfaction system of animals is still a daunting challenge. Herein, we propose a core-sheath pillar (CSP) architecture with a perfect synergistic interface that effectively integrates the advantages of metal-organic frameworks and metal oxides to tackle the above-mentioned challenge. The sheath material, NH2-MIL-125, can concentrate target analyte, nitro-explosives, by 1012 times from its vapour. The perfect band-matched synergistic interface enables the TiO2 core to effectively harvest and utilize visible light. At room temperature and under visible light, CSP (TiO2, NH2-MIL-125) shows an unexpected self-promoting analyte-sensing behaviour. Its experimentally reached limit of detection (â¼0.8 ppq, hexogeon) is 103 times lower than the lowest one achieved by a sniffer dog or all sensing techniques without analyte pre-concentration. Moreover, the sensor exhibits excellent selectivity against commonly existing interferences, with a short response time of 0.14 min.
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Bocaviruses are typical zoonotic pathogens with a wide range of hosts. Here, we report the detection of human bocavirus (HBoV) in Rattus norvegicus captured in China and the results of sequencing and phylogenetic analysis based on the partial VP1 region and the entire viral genome. A total of 357 fecal samples from rats were collected in 2015-2017 and analyzed for HBoV using PCR. The detection rate of HBoV was 0.84% (3/357). Phylogenetic analysis revealed that this virus is genetically closely related to HBoV-2. R. norvegicus may be a carrier of HBoV, and its impact on public health merits attention.
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Bocavirus , Gastroenteritis , Bocavirus Humano , Infecciones por Parvoviridae , Animales , Bocavirus/genética , China/epidemiología , Heces , Bocavirus Humano/genética , Infecciones por Parvoviridae/epidemiología , Infecciones por Parvoviridae/veterinaria , Filogenia , RatasRESUMEN
BACKGROUND: A recent study has reported that patients with nonalcoholic fatty liver disease (NAFLD) are more susceptible to coronary microvascular dysfunction (CMD), which may predict major adverse cardiac events. However, little is known regarding the causes of CMD during NAFLD. In this study, we aimed to explore the role of hepatic small extracellular vesicles (sEVs) in regulating the endothelial dysfunction of coronary microvessels during NAFLD. RESULTS: We established two murine NAFLD models by feeding mice a methionine-choline-deficient (MCD) diet for 4 weeks or a high-fat diet (HFD) for 16 weeks. We found that the NOD-like receptor family, pyrin domain containing 3 (NLRP3) inflammasome-dependent endothelial hyperpermeability occurred in coronary microvessels during both MCD diet and HFD-induced NAFLD. The in vivo and in vitro experiments proved that novel-microRNA(miR)-7-abundant hepatic sEVs were responsible for NLRP3 inflammasome-dependent endothelial barrier dysfunction. Mechanistically, novel-miR-7 directly targeted lysosomal associated membrane protein 1 (LAMP1) and promotes lysosomal membrane permeability (LMP), which in turn induced Cathepsin B-dependent NLRP3 inflammasome activation and microvascular endothelial hyperpermeability. Conversely, a specific novel-miR-7 inhibitor markedly improved endothelial barrier integrity. Finally, we proved that steatotic hepatocyte was a significant source of novel-miR-7-contained hepatic sEVs, and steatotic hepatocyte-derived sEVs were able to promote NLRP3 inflammasome-dependent microvascular endothelial hyperpermeability through novel-miR-7. CONCLUSIONS: Hepatic sEVs contribute to endothelial hyperpermeability in coronary microvessels by delivering novel-miR-7 and targeting the LAMP1/Cathepsin B/NLRP3 inflammasome axis during NAFLD. Our study brings new insights into the liver-to-microvessel cross-talk and may provide a new diagnostic biomarker and treatment target for microvascular complications of NAFLD.
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Permeabilidad Capilar/efectos de los fármacos , Endotelio Vascular/efectos de los fármacos , Vesículas Extracelulares , MicroARNs/metabolismo , Enfermedad del Hígado Graso no Alcohólico , Animales , Extractos Celulares/farmacología , Vasos Coronarios/efectos de los fármacos , Vesículas Extracelulares/química , Vesículas Extracelulares/metabolismo , Hepatocitos/química , Inflamasomas/efectos de los fármacos , Hígado/citología , Masculino , Ratones , Ratones Endogámicos C57BL , Microvasos/efectos de los fármacos , Proteína con Dominio Pirina 3 de la Familia NLR , Enfermedad del Hígado Graso no Alcohólico/metabolismo , Enfermedad del Hígado Graso no Alcohólico/fisiopatologíaRESUMEN
BACKGROUND: Antituberculosis-drug resistance is an important public health issue, and its epidemiological patterns has dramatically changed in recent decades. This study aimed to estimate the trends of multidrug-resistant tuberculosis (MDR-TB), which can be used to inform health strategies. METHODS: Data were collected from the Global Burden of Disease study 2017. The estimated annual percentage changes (EAPCs) were calculated to assess the trends of MDR-TB burden at global, regional, and national level from 1990 to 2017 using the linear regression model. RESULTS: Globally, the age-standardized rate (ASR) of MDR-TB burden including incidence, prevalence, death and disability-adjusted life years (DALYs) had pronounced increasing trends from 1990 to 1999, with the EAPCs were 17.63 [95% confidence interval (CI): 10.77-24.92], 17.57 (95% CI 11.51-23.95), 21.21 (95% CI 15.96-26.69), and 21.90 (95% CI 16.55-27.50), respectively. Particularly, the largest increasing trends were seen in areas and countries with low and low-middle sociodemographic index (SDI). However, the trends in incidence, prevalence, death and DALYs of MDR-TB decreased globally from 2000 to 2017, with the respective EAPCs were - 1.37 (95% CI - 1.62 to - 1.12), - 1.32 (95% CI - 1.38 to - 1.26), - 3.30 (95% CI - 3.56 to - 3.04) and - 3.32 (95% CI - 3.59 to - 3.06). Decreasing trends of MDR-TB were observed in most regions and countries, particularly that of death and DALYs in Slovenia were - 18.96 (95% CI - 20.82 to - 17.06) and -19.35 (95% CI - 21.10 to - 17.55), respectively. Whereas the pronounced increasing trends of MDR-TB occurred in Papua New Guinea, Singapore, and Australia. CONCLUSIONS: The ASR of MDR-TB showed pronounced decreasing trends from 2000 to 2017. However, the MDR-TB burden remains a substantial challenge to the TB control globally, and requires effective control strategies and healthcare systems.
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Salud Global/estadística & datos numéricos , Tuberculosis Resistente a Múltiples Medicamentos/epidemiología , Adolescente , Adulto , Anciano , Niño , Preescolar , Femenino , Salud Global/tendencias , Humanos , Masculino , Persona de Mediana Edad , Prevalencia , Años de Vida Ajustados por Calidad de Vida , Adulto JovenRESUMEN
BACKGROUND: Rattus norvegicus and Suncus murinus are important reservoirs of zoonotic bacterial diseases. An understanding of the composition of gut and oropharynx bacteria in these animals is important for monitoring and preventing such diseases. We therefore examined gut and oropharynx bacterial composition in these animals in China. RESULTS: Proteobacteria, Firmicutes and Bacteroidetes were the most abundant phyla in faecal and throat swab samples of both animals. However, the composition of the bacterial community differed significantly between sample types and animal species. Firmicutes exhibited the highest relative abundance in throat swab samples of R. norvegicus, followed by Proteobacteria and Bacteroidetes. In throat swab specimens of S. murinus, Proteobacteria was the predominant phylum, followed by Firmicutes and Bacteroidetes. Firmicutes showed the highest relative abundance in faecal specimens of R. norvegicus, followed by Bacteroidetes and Proteobacteria. Firmicutes and Proteobacteria had almost equal abundance in faecal specimens of S. murinus, with Bacteroidetes accounting for only 3.07%. The family Streptococcaceae was most common in throat swab samples of R. norvegicus, while Prevotellaceae was most common in its faecal samples. Pseudomonadaceae was the predominant family in throat swab samples of S. murinus, while Enterobacteriaceae was most common in faecal samples. We annotated 33.28% sequences from faecal samples of S. murinus as potential human pathogenic bacteria, approximately 3.06-fold those in R. norvegicus. Potential pathogenic bacteria annotated in throat swab samples of S. murinus were 1.35-fold those in R. norvegicus. CONCLUSIONS: Bacterial composition of throat swabs and faecal samples from R. norvegicus differed from those of S. murinus. Both species carried various pathogenic bacteria, therefore both should be closely monitored in the future, especially for S. murinus.
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Bacterias/clasificación , ARN Ribosómico 16S/análisis , Ratas/microbiología , Musarañas/microbiología , Animales , Bacterias/genética , China , Heces/microbiología , Microbiota , Orofaringe/microbiologíaRESUMEN
BACKGROUND: Murine kobuviruses (MuKV) are newly recognized picornaviruses first detected in murine rodents in the USA in 2011. Little information on MuKV epidemiology in murine rodents is available. Therefore, we conducted a survey of the prevalence and genomic characteristics of rat kobuvirus in Guangdong, China. RESULTS: Fecal samples from 223 rats (Rattus norvegicus) were collected from Guangdong and kobuviruses were detected in 12.6% (28) of samples. Phylogenetic analysis based on partial 3D and complete VP1 sequence regions showed that rat kobuvirus obtained in this study were genetically closely related to those of rat/mouse kobuvirus reported in other geographical areas. Two near full-length rat kobuvirus genomes (MM33, GZ85) were acquired and phylogenetic analysis of these revealed that they shared very high nucleotide/amino acids identity with one another (95.4%/99.4%) and a sewage-derived sequence (86.9%/93.5% and 87.5%/93.7%, respectively). Comparison with original Aichivirus A strains, such human kobuvirus, revealed amino acid identity values of approximately 80%. CONCLUSION: Our findings indicate that rat kobuvirus have distinctive genetic characteristics from other Aichivirus A viruses. Additionally, rat kobuvirus may spread via sewage.
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Genoma Viral , Kobuvirus/clasificación , Infecciones por Picornaviridae/epidemiología , Secuenciación Completa del Genoma/métodos , Animales , Proteínas de la Cápside/genética , China/epidemiología , Heces/virología , Kobuvirus/genética , Kobuvirus/aislamiento & purificación , Filogenia , Infecciones por Picornaviridae/veterinaria , Prevalencia , Ratas , Análisis de Secuencia de ARN , Aguas del Alcantarillado/virologíaRESUMEN
BACKGROUND: Bladder cancer is the fourth most common malignancy in men and a considerable disease burden globally. Multiple studies have focused on the accuracy of optical coherence tomography for bladder cancer diagnosis; however, the findings are inconsistent. Here, we assessed the accuracy of optical coherence tomography for bladder cancer diagnosis. METHODS: Embase, PubMed, Medline, Web of Science, and the Cochrane Library database were searched for relevant studies from the earliest date available through March 11, 2019. Studies evaluating the accuracy of optical coherence tomography bladder cancer diagnosis were included. Pooled sensitivity, specificity, and area under the curve values of weighted symmetric summary receiver operating curves, were calculated at the per-lesion level. RESULTS: Eleven studies, with a total of 1933 lesions, were included in the final analysis. The pooled results indicated that optical coherence tomography can differentiate bladder cancer from benign lesions: sensitivity, 94.9% (95% confidence interval: 92.7%-96.6%); specificity, 84.6% (95% confidence interval: 82.6%-86.4%); area under the curve, 0.97. Moreover, compared with optical coherence tomography alone, combined optical coherence tomography and fluorescence cystoscopy increased the diagnostic accuracy (sensitivity, 94.3% vs. 87.3%; specificity, 89.2% vs. 73.9%). Cross-polarization optical coherence tomography could also distinguish bladder cancer from normal tissue: sensitivity, 92.0% (95% confidence interval: 87.0%-95.6%); specificity, 84.4% (95% confidence interval: 81.7%-86.9%); area under the curve, 0.95. CONCLUSIONS: Optical coherence tomography can accurately differentiate malignant from benign bladder lesions, particularly when combined with fluorescence cystoscopy.
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Tomografía de Coherencia Óptica/métodos , Neoplasias de la Vejiga Urinaria/diagnóstico , Cistoscopía/métodos , Fluorescencia , Humanos , Sensibilidad y Especificidad , Tomografía de Coherencia Óptica/normas , Neoplasias de la Vejiga Urinaria/patologíaRESUMEN
CONTEXT: The patterns of associations between glycated Hb (HbA1c) and mortality are still unclear. OBJECTIVE: To explore the extent to which ranges of HbA1c levels are associated with the risk of mortality among participants with and without diabetes. DESIGN, SETTING, AND PATIENTS: This was a nationwide, community-based prospective cohort study. Included were 15,869 participants (median age 64 years) of the Health and Retirement Study, with available HbA1c data and without a history of cancer. Cox proportional hazards regression models were used to estimate hazard ratios with 95% CIs for mortality. RESULTS: A total of 2133 participants died during a median follow-up of 5.8 years. In participants with diabetes, those with an HbA1c level of 6.5% were at the lowest risk of all-cause mortality. When HbA1c level was <5.6% or >7.4%, the increased all-cause mortality risk became statistically significant as compared with an HbA1c level of 6.5%. As for participants without diabetes, those with an HbA1c level of 5.4% were at the lowest risk of all-cause mortality. When the HbA1c level was <5.0%, the increased all-cause mortality risk became statistically significant as compared with an HbA1c level of 5.4%. However, we did not observe a statistically significant elevated risk of all-cause mortality above an HbA1c level of 5.4%. CONCLUSIONS: A U-shaped and reverse J-shaped association for all-cause mortality was found among participants with and without diabetes. The corresponding optimal ranges for overall survival are predicted to be 5.6% and 7.4% and 5.0% and 6.5%, respectively.
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Diabetes Mellitus/mortalidad , Hemoglobina Glucada/análisis , Anciano , Causas de Muerte , Diabetes Mellitus/sangre , Femenino , Humanos , Estudios Longitudinales , Masculino , Persona de Mediana Edad , Modelos de Riesgos Proporcionales , Estudios Prospectivos , Tasa de SupervivenciaRESUMEN
RATIONAL: Knee joint infection caused by isolated primary Candida is extremely rare, with only a few cases reported. It occurs most often in patients with predisposing factors (e.g., immunosuppression, malignancy, drug abuse) or fungal invasion during traumatic procedures, including surgery. We report an unusual case of Candida parapsilosis infection in the knee joint with no predisposing factors. PATIENT CONCERNS: A 65-year-old man entered our hospital complaining of persistent pain and mild swelling of the right knee that seriously affected normal walking. There was no obvious cause for his distress. DIAGNOSIS: The case was eventually diagnosed as a primary Candida parapsilosis infection which had many diagnostic particularities and difficulties. INTERVENTIONS: Total knee arthroplasty (TKA) was ultimately performed followed by fluconazole coverage. OUTCOMES: The patient showed good clinical performance at the 3- and 6-month follow-up visits and was very satisfied with the therapeutic effect. LESSONS: If there were suspected symptoms of primary Candida infection cases, imaging and microscopic examinations, tissue cultures, and pathological examination of the puncture knee joint fluid were required.
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Artritis Infecciosa/diagnóstico , Artritis Infecciosa/microbiología , Candida parapsilosis , Candidiasis/diagnóstico , Articulación de la Rodilla , Anciano , Antifúngicos/uso terapéutico , Artritis Infecciosa/terapia , Artroplastia de Reemplazo de Rodilla , Candidiasis/terapia , Humanos , MasculinoRESUMEN
OBJECTIVE: To investigate the prevalence of the adeno-associated virus (AAV) in murine rodents and house shrews in 4 provinces of China. METHODS: A total of 469 murine rodents and 19 house shrews were captured between May 2015 and May 2017. Cap gene of AAV sequences was obtained to evaluate the genetic characteristics of rat AAV. RESULTS: Rat AAVs were found in 54.7% (267/488) of throat swabs, 14.3% (70/488) of fecal samples, and 18.4% (41/223) of serum samples. Rat AAVs were detected in 3 species of murine rodents including Rattus norvegicus (34.8%), R. tanezumi (43.0%), and R. losea (2.3%), and house shrews (Suncus murinus) (26.1%) from the selected sampling sites. Fourteen near-full-length Cap gene sequences, ranging in length from 2,156 to 2,169 nt, were isolated from the fecal samples of R. norvegicus and R. tanezumi. These 14 sequences shared a high identity of 97.4% at the nucleotide level and 99.1% at the amino acid level. Phylogenetic analysis showed that the rat AAV formed a distinct clade, distinguishable from the AAV discovered in humans and in other animals. CONCLUSIONS: A high prevalence of rat AAV that was highly conserved within the Cap gene was found in 3 common murine rodents and house shrews in China.
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Portador Sano/veterinaria , Portador Sano/virología , Dependovirus , Infecciones por Parvoviridae/veterinaria , Ratas/virología , Musarañas/virología , Animales , China/epidemiología , ADN Viral/genética , Heces/virología , Infecciones por Parvoviridae/sangre , Faringe/virología , Filogenia , Prevalencia , Roedores/virologíaRESUMEN
In this study, we detected and genetically characterized rat bocavirus (RBoV) carried in 496 murine rodents that were captured in four provinces in China between May 2015 and May 2017. RBoV-positive samples were found in all four provinces, with a total positive rate of 24.8% (123/496) in throat swabs and 58.1% (286/492) in fecal samples. Twelve nearly full-length genome sequences of RBoV were determined, and the average sequence identity was 96.2%. Phylogenetic analysis showed that RBoVs formed a distinct clade that was distinguishable from the bocaviruses discovered in humans and other animals.
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Bocavirus/aislamiento & purificación , Heces/virología , Orofaringe/virología , Infecciones por Parvoviridae/veterinaria , Enfermedades de los Roedores/virología , Animales , Bocavirus/clasificación , Bocavirus/genética , Genoma Viral , Infecciones por Parvoviridae/virología , Filogenia , Ratas , RoedoresRESUMEN
The role of hybrid fibers as intermediates in fiber type transformations is not completely understood. In some cases hybrids are clearly transitional fibers changing from one type to another, but in others they represent phenotypically stable fibers in normal muscles. In the current study, our goal was to understand the fate of hybrid fibers in fiber type transitions that take place during muscle maturation. Previous studies have reported high proportions of hybrid fibers during postnatal development, but few have followed the fate of these fibers past the time of weaning. We quantified proportions of hybrid fibers in three different mouse skeletal muscles from newly weaned to 6-month-old mice. Hybrid fibers were very prevalent in the brachioradialis (BR) and tibialis anterior (TA) muscles from newly weaned mice, where they constituted 50 and 40% of the fibers, respectively. These hybrids declined steadily to about 15-30% over the next several months. In the soleus muscle the proportion of hybrids did not change, but constituted approximately 20% of fibers. The reduction in IIX/IIB hybrids resulted from different processes in the BR and the TA. In the BR, the reduction was coincident with an increase in type IIX fibers. In the TA, the number of IIX/IIB hybrids was inversely correlated with the proportion of IIB fibers. These patterns reveal that the role of hybrid fibers as intermediates in muscle development is complex. Some hybrid fibers in maturing muscles represent transitional fiber types, while others are phenotypically stable. Moreover, the fate of transitional fibers may be distinct among similar fiber types within different muscles.
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Desarrollo de Músculos/fisiología , Fibras Musculares Esqueléticas/citología , Cadenas Pesadas de Miosina/metabolismo , Animales , Electroforesis en Gel de Poliacrilamida , Femenino , Masculino , Ratones , Ratones Endogámicos C57BL , Fibras Musculares Esqueléticas/metabolismoRESUMEN
The excited-state proton transfer (ESPT) via proton transfer wires in green fluorescent protein (GFP) plays an important role on the spectroscopic of GFP. In this work, we use the proton transfer wires and the chromophore complex to simulate the tautomer structures of neutral state and the intermediate state in wt-GFP. And we employ the time-dependent density functional theory combined with the sum-over-states method to calculate the one- and two-photon absorption properties of these complexes in GFP. We obtain the large stokes shift from 383 nm to 500 nm in GFP when simulating the ESPT process by these isomerous H-bonding complexes. We find that the TPA spectrum of the H-bonding complex of the intermediate state agrees more with experimental measurement than that of the H-bonding complex of the neutral state. The TPA spectrum of GFP might be mainly dominated by the structure which is similar to the H-bonding complex of intermediate state. Further, we simulate another kind of complex which possess short-strong hydrogen bonds in proton transfer wires, and find that TPA properties of these complexes are much stronger than that of the complexes with the long distance proton wires from GFP.
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Proteínas Fluorescentes Verdes/química , Protones , Teoría Cuántica , AbsorciónRESUMEN
LSSmKate1 and LSSmKate2 are monomeric red fluorescent proteins (RFPs) with large Stokes shifts (LSS). The hydrogen-bonding (H-bonding) network within LSSmKate1 or LSSmKate2, which is composed of a chromophore and some surrounding amino acid residues, supports their special spectral properties. In this work, we propose H-bonding complex models to simulate the H-bonding network of LSSmKate1 and LSSmKate2 and employ the time-dependent density functional theory combining with the sum-overstates method to calculate their one- and two-photon absorption characters. We discuss the influence of the hydrogen bond on the one- and two-photon absorption properties of these H-bonding complexes through intermolecular hyperconjugation of the hydrogen-bond form.
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Proteínas Luminiscentes/química , Modelos Químicos , Absorciometría de Fotón , Enlace de Hidrógeno , Conformación Proteica , Proteína Fluorescente RojaRESUMEN
Although skeletal muscle fiber types are often defined as belonging to discrete categories, many muscles possess fibers with intermediate phenotypes. These hybrid fiber types can be identified by their expression of two or more myosin heavy chain (MHC) isoforms within the same single fiber. In mouse muscles, the most common hybrid fibers are those coexpressing the IIX and IIB MHC isoforms. In the present study, we focused on these IIX/IIB fibers from normal mouse muscles to determine the relative proportions of MHC isoforms at both the protein and mRNA levels and to examine the longitudinal distribution of isoforms within single fibers. We found that IIX/IIB hybrids represent â¼25 and 50% of the fibers in the mouse tibialis anterior and brachioradialis, respectively. The relative proportion of the IIX and IIB isoforms in these fibers spans a continuum, from predominantly IIB-like hybrids to IIX-like hybrids. Quantitative assessment of mRNA levels using real-time PCR from single fibers indicated that IIB expression dominated over IIX expression in most fibers and that a general correlation existed between mRNA isoform levels and MHC protein content. However, the match between mRNA levels and protein content was not precise. Finally, we measured MHC isoform proportions in adjacent fiber segments and discovered that â¼30% of hybrids possessed significant differences in isoform content along their length. In some instances, the muscle fiber type as defined by MHC content changed completely along the length of a fiber. This pattern of asymmetrical MHC isoform content along the length of single fibers suggests that the multiple myonuclei of a muscle fiber may express distinct myofibrillar isoforms in an uncoordinated fashion.