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1.
Cell ; 139(2): 312-24, 2009 Oct 16.
Artigo em Inglês | MEDLINE | ID: mdl-19837034

RESUMO

Human mitochondrial DNA polymerase (Pol gamma) is the sole replicase in mitochondria. Pol gamma is vulnerable to nonselective antiretroviral drugs and is increasingly associated with mutations found in patients with mitochondriopathies. We determined crystal structures of the human heterotrimeric Pol gamma holoenzyme and, separately, a variant of its processivity factor, Pol gammaB. The holoenzyme structure reveals an unexpected assembly of the mitochondrial DNA replicase where the catalytic subunit Pol gammaA interacts with its processivity factor primarily via a domain that is absent in all other DNA polymerases. This domain provides a structural module for supporting both the intrinsic processivity of the catalytic subunit alone and the enhanced processivity of holoenzyme. The Pol gamma structure also provides a context for interpreting the phenotypes of disease-related mutations in the polymerase and establishes a foundation for understanding the molecular basis of toxicity of anti-retroviral drugs targeting HIV reverse transcriptase.


Assuntos
Replicação do DNA , DNA Mitocondrial/metabolismo , DNA Polimerase Dirigida por DNA/química , DNA Polimerase Dirigida por DNA/genética , Sequência de Aminoácidos , Cristalografia por Raios X , DNA Polimerase gama , Humanos , Modelos Moleculares , Dados de Sequência Molecular , Doenças do Sistema Nervoso/genética , Alinhamento de Sequência
2.
Breast Cancer Res Treat ; 199(1): 207-214, 2023 May.
Artigo em Inglês | MEDLINE | ID: mdl-36882607

RESUMO

BACKGROUND: Characterization of the breast cancer (BC) immune response may provide information for a point of intervention, such as application of immunotherapeutic treatments. In this study, we sought to recover and characterize the adaptive immune receptor (IR) recombination reads from genomics files representing Kenyan patients, to better understand the immune response specifically related to those patients. METHODS: We used a previously applied algorithm and software to obtain productive IR recombination reads from cancer and adjacent normal tissue samples representing 22 Kenyan BC patients. RESULTS: From both the RNAseq and exome files, there were significantly more T-cell receptor (TCR) recombination reads recovered from tumor samples compared to marginal tissue samples. Also, the immunoglobulin (IG) genes were expressed at a much higher level than the TCR genes (p-value = 0.0183) in the tumor samples. And, the tumor IG CDR3s consistently represented more positively charged amino acid R-groups, in comparison to the marginal tissue, IG CDR3s. CONCLUSION: For Kenyan patients, a high level of IG expression, representing specific CDR3 chemistries, was associated with BC. These results lay the foundation for studies that could support specific immunotherapeutic interventions for Kenyan BC patients.


Assuntos
Neoplasias da Mama , Linfócitos T , Humanos , Feminino , Neoplasias da Mama/genética , Neoplasias da Mama/terapia , Quênia/epidemiologia , Genes de Imunoglobulinas , Receptores de Antígenos de Linfócitos T/genética
3.
Langmuir ; 37(18): 5447-5456, 2021 May 11.
Artigo em Inglês | MEDLINE | ID: mdl-33929862

RESUMO

Precise tailoring of two-dimensional nanosheets with organic molecules is critical to passivate the surface and control the reactivity, which is essential for a wide range of applications. Herein, we introduce catechols to functionalize exfoliated MXenes (Ti3C2Tx) in a colloidal suspension. Catechols react spontaneously with Ti3C2Tx surfaces, where binding is initiated from a charge-transfer complex as confirmed by density functional theory (DFT) and UV-vis. Ti3C2Tx sheet interlayer spacing is increased by catechol functionalization, as confirmed by X-ray diffraction (XRD), while Raman and atomic force microscopy-infrared spectroscopy (AFM-IR) measurements indicate binding of catechols at the Ti3C2Tx surface occurs through metal-oxygen bonds, which is supported by DFT calculations. Finally, we demonstrate immobilization of a fluorescent dye on the surface of MXene. Our results establish a strategy for tailoring MXene surfaces via aqueous functionalization with catechols, whereby colloidal stability can be modified and further functionality can be introduced, which could provide excellent anchoring points to grow polymer brushes and tune specific properties.

4.
Eur J Neurol ; 25(6): 848-853, 2018 06.
Artigo em Inglês | MEDLINE | ID: mdl-29493845

RESUMO

BACKGROUND AND PURPOSE: We aimed to test the clinical utility of the leg:thigh intraepidermal nerve-fiber (IENF) density ratio as a parameter to discriminate between length-dependent small-fiber neuropathy (SFN) and small-fiber sensory ganglionopathy (SFSG) in subjects with signs and symptoms of small-fiber pathology. METHODS: We retrospectively evaluated thigh and leg IENF density in 314 subjects with small-fiber pathology (173 with distal symmetrical length-dependent SFN and 141 with non-length-dependent SFSG). A group of 288 healthy subjects was included as a control group. The leg:thigh IENF density ratio was calculated for all subjects. We used receiver operating characteristic curve analyses to assess the ability of this parameter to discriminate between length-dependent SFN and SFSG, and the decision curve analysis to estimate its net clinical benefit. RESULTS: In patients with neuropathy, the mean IENF density was 14.8 ± 6.8/mm at the thigh (14.0 ± 6.9/mm in length-dependent SFN and 15.9 ± 6.7/mm in patients with SFSG) and 7.5 ± 4.5/mm at the distal leg (5.4 ± 3.2/mm in patients with length-dependent SFN and 10.1 ± 4.6/mm in patients with SFSG). The leg:thigh IENF density ratio was significantly (P < 0.01) lower in patients with length-dependent SFN (0.44 ± 0.23) compared with patients with SFSG (0.68 ± 0.28). The area under the curve of the receiver operating characteristic analysis to discriminate between patients with length-dependent SFN and SFSG was 0.79. The decision curve analysis demonstrated the clinical utility of this parameter. CONCLUSIONS: The leg:thigh IENF ratio represents a valuable tool in the differential diagnosis between SFSG and length-dependent SFN.


Assuntos
Fibras Nervosas/patologia , Doenças do Sistema Nervoso Periférico/diagnóstico , Pele/patologia , Neuropatia de Pequenas Fibras/diagnóstico , Adulto , Idoso , Biópsia , Diagnóstico Diferencial , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Doenças do Sistema Nervoso Periférico/patologia , Estudos Retrospectivos , Neuropatia de Pequenas Fibras/patologia
6.
Br J Dermatol ; 176(1): 209-211, 2017 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-27088428

RESUMO

Dermatomyositis (DM) is commonly associated with scalp pruritus that can be severe. In addition, significant crawling and burning sensations have been reported in these cases. The aetiology of these scalp sensations in the context of DM is not fully understood. We report a 42-year-old female with treatment-resistant DM and structural changes in scalp epidermal and dermal nerve fibres. The patient presented with characteristic skin manifestations (Gottron's papules and poikiloderma), severely pruritic scalp, intermittent muscle weakness on neurological exam with electrodiagnostically confirmed myositis, and joint pain. Structural changes in scalp epidermal and dermal nerve fibres were discovered in a skin biopsy, suggesting that small-fibre neuropathy associated with scalp pruritus may be a manifestation of the DM syndrome. Further clinical experience combined with selective skin biopsy in patients with DM and symptomatic scalp will help determine the frequency of coexistent small nerve fibre involvement. Based on our limited findings, we suggest that pruritus in DM may be associated with abnormal epidermal and dermal nerve fibre structure.


Assuntos
Dermatomiosite/complicações , Prurido/etiologia , Dermatoses do Couro Cabeludo/complicações , Neuropatia de Pequenas Fibras/etiologia , Adulto , Dermatomiosite/diagnóstico por imagem , Feminino , Humanos , Microscopia Confocal , Debilidade Muscular/etiologia , Dermatoses do Couro Cabeludo/diagnóstico por imagem , Neuropatia de Pequenas Fibras/diagnóstico por imagem
7.
Eur J Neurol ; 23(2): 333-8, 2016 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-26493160

RESUMO

BACKGROUND AND PURPOSE: Quantification of intraepidermal nerve fibers (IENFs) in skin biopsies is now the tool of choice to diagnose small fiber neuropathies. An adequate normative dataset, necessary to assess normality cutoffs, is available for brightfield microscopy but not for immunofluorescence. METHODS: Intraepidermal nerve fiber density data in distal leg skin samples processed with immunofluorescence were collected from 528 healthy individuals from four experienced laboratories worldwide. In all laboratories skin samples were collected, processed and analyzed according to standard procedures. Quantile regression analysis was employed to tailor the fit of the 5° percentile as the normal cutoff value and to test and measure the effect of age, gender, body mass index, race, biopsy site (lateral distal lower leg or medial posterior mid-calf) and participating laboratory as possible influential variables. RESULTS: Age, gender and biopsy site showed an independent linear correlation with IENF density. For each decade the 5° quantile IENF cutoff showed a 0.54 fibers/mm decrease, whilst females exhibited a 1.0 fiber/mm cutoff greater than males. Compared to the lateral distal lower leg, biopsies from the calf showed a 3.4 fibers/mm lower 5° percentile cutoff, documenting a variation linked by site. CONCLUSIONS: An age- and gender-adjusted normative dataset for IENF density at the lateral distal lower leg obtained with indirect immunofluorescence is presented for the first time by sharing data from four experienced laboratories worldwide. This dataset can be used as reference for laboratories processing skin biopsies with this technique.


Assuntos
Epiderme/inervação , Perna (Membro)/inervação , Fibras Nervosas , Adulto , Feminino , Imunofluorescência , Humanos , Masculino , Pessoa de Meia-Idade , Doenças do Sistema Nervoso Periférico/diagnóstico , Valores de Referência
8.
Pediatr Blood Cancer ; 61(2): 360-2, 2014 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-23900766

RESUMO

Children with ataxia-telangiectasia (A-T) and cancer have a poorer prognosis due in part to increased treatment-related toxicity. We piloted a curative intent approach in five children with A-T who presented with advanced stage (III, n = 2; IV, n = 3) B-NHL (diffuse large B-cell lymphoma, n = 4; Burkitt leukemia, n = 1) using a modified LMB-based protocol. Two achieved sustained CCR (one, CCR at 6 years; one, pulmonary death after 3 years in CCR). Two died from toxicity during induction and 1 failed induction with progressive disease. Novel therapeutic approaches which overcome drug resistance and are less toxic are needed for children with A-T and B-NHL.


Assuntos
Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Ataxia Telangiectasia/tratamento farmacológico , Linfoma de Células B/tratamento farmacológico , Adulto , Ataxia Telangiectasia/complicações , Criança , Ciclofosfamida/uso terapêutico , Citarabina/uso terapêutico , Doxorrubicina/uso terapêutico , Etoposídeo/uso terapêutico , Feminino , Seguimentos , Humanos , Hidrocortisona/uso terapêutico , Leucovorina/uso terapêutico , Linfoma de Células B/complicações , Masculino , Metotrexato/uso terapêutico , Estadiamento de Neoplasias , Projetos Piloto , Prednisona/uso terapêutico , Prognóstico , Estudos Prospectivos , Vincristina/uso terapêutico , Adulto Jovem
9.
Nanoscale ; 16(17): 8369-8377, 2024 May 02.
Artigo em Inglês | MEDLINE | ID: mdl-38572999

RESUMO

As thin films of semiconducting covalent organic frameworks (COFs) are demonstrating utility for ambipolar electronics, channel materials in organic electrochemical transistors (OECTs), and broadband photodetectors, control and modulation of their thin film properties is paramount. In this work, an interfacial growth technique is utilized to synthesize imine TAPB-PDA COF films at both the liquid-liquid interface as well as at the liquid-solid interface on a Si/SiO2 substrate. The concentration of acetic acid catalyst in the aqueous phase is shown to significantly influence the thin film morphology of the liquid-solid growth, with concentrations below 1 M resulting in no film nucleation, concentrations of 1-4 M enabling smooth film formation, and concentrations greater than 4 M resulting in films with a higher density of particulates on the surface. Importantly, while the films grown at the liquid-liquid interface are mixed-orientation, those grown directly at the liquid-solid interface on the Si/SiO2 surface have highly oriented COF layers aligned parallel to the substrate surface. Moreover, this liquid-solid growth process affords TAPB-PDA COF thin films with p-type charge transport having a transconductance of 10 µS at a gate voltage of -0.9 V in an OECT device structure.

10.
J Pharmacol Exp Ther ; 347(2): 478-86, 2013 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-23975906

RESUMO

Calcitonin gene-related peptide (CGRP) is a potent neuropeptide whose agonist interaction with the CGRP receptor (CGRP-R) in the periphery promotes vasodilation, neurogenic inflammation and trigeminovascular sensory activation. This process is implicated in the cause of migraine headaches, and CGRP-R antagonists in clinical development have proven effective in treating migraine-related pain in humans. CGRP-R is expressed on blood vessel smooth muscle and sensory trigeminal neurons and fibers in the periphery as well as in the central nervous system. However, it is not clear what role the inhibition of central CGRP-R plays in migraine pain relief. To this end, the CGRP-R positron emission tomography (PET) tracer [(11)C]MK-4232 (2-[(8R)-8-(3,5-difluorophenyl)-6,8-[6-(11)C]dimethyl-10-oxo-6,9-diazaspiro[4.5]decan-9-yl]-N-[(2R)-2'-oxospiro[1,3-dihydroindene-2,3'-1H-pyrrolo[2,3-b]pyridine]-5-yl]acetamide) was discovered and developed for use in clinical PET studies. In rhesus monkeys and humans, [(11)C]MK-4232 displayed rapid brain uptake and a regional brain distribution consistent with the known distribution of CGRP-R. Monkey PET studies with [(11)C]MK-4232 after intravenous dosing with CGRP-R antagonists validated the ability of [(11)C]MK-4232 to detect changes in CGRP-R occupancy in proportion to drug plasma concentration. Application of [(11)C]MK-4232 in human PET studies revealed that telcagepant achieved only low receptor occupancy at an efficacious dose (140 mg PO). Therefore, it is unlikely that antagonism of central CGRP-R is required for migraine efficacy. However, it is not known whether high central CGRP-R antagonism may provide additional therapeutic benefit.


Assuntos
Acetanilidas/farmacocinética , Analgésicos/farmacocinética , Azepinas/farmacocinética , Encéfalo/metabolismo , Antagonistas do Receptor do Peptídeo Relacionado ao Gene de Calcitonina , Imidazóis/farmacocinética , Tomografia por Emissão de Pósitrons/métodos , Compostos Radiofarmacêuticos/farmacocinética , Compostos de Espiro/farmacocinética , Acetanilidas/química , Adulto , Analgésicos/uso terapêutico , Animais , Azepinas/uso terapêutico , Encéfalo/diagnóstico por imagem , Radioisótopos de Carbono , Feminino , Humanos , Imidazóis/uso terapêutico , Macaca mulatta , Masculino , Pessoa de Meia-Idade , Transtornos de Enxaqueca/tratamento farmacológico , Transtornos de Enxaqueca/metabolismo , Estrutura Molecular , Ligação Proteica , Compostos Radiofarmacêuticos/química , Especificidade da Espécie , Compostos de Espiro/química , Distribuição Tecidual , Adulto Jovem
11.
Heliyon ; 9(7): e18175, 2023 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-37519716

RESUMO

Rift Valley Fever (RVF) is a mosquito-borne viral disease caused by the Rift Valley Fever Virus. The disease is a zoonosis that largely affects domestic animals, including sheep, goats, and cattle, resulting in severe morbidity and mortality marked by massive storm abortions. To halt human and livestock deaths due to RVF, the development of efficacious vaccines and therapeutics is a compelling and urgent priority. We sought to identify potential key modules (gene clusters), hub genes, and regulatory motifs involved in the pathogenesis of RVF in Bos taurus that are amenable to inhibition. We analyzed 39 Bos taurus RNA-Seq samples using the weighted gene co-expression network analysis (WGCNA) R package and uncovered significantly enriched modules containing genes with potential pivotal roles in RVF progression. Moreover, regulatory motif analysis conducted using the Multiple Expectation Maximization for Motif Elicitation (MEME) suite identified motifs that probably modulate vital biological processes. Gene ontology terms associated with identified motifs were inferred using the GoMo human database. The gene co-expression network constructed in WGCNA using 5000 genes contained seven (7) modules, out of which four were significantly enriched for terms associated with response to viruses, response to interferon-alpha, innate immune response, and viral defense. Additionally, several biological pathways implicated in developmental processes, anatomical structure development, and multicellular organism development were identified. Regulatory motifs analysis identified short, repeated motifs whose function(s) may be amenable to disruption by novel therapeutics. Predicted functions of identified motifs include tissue development, embryonic organ development, and organ morphogenesis. We have identified several hub genes in enriched co-expressed gene modules and regulatory motifs potentially involved in the pathogenesis of RVF in B. taurus that are likely viable targets for disruption by novel therapeutics.

12.
Front Res Metr Anal ; 8: 1070390, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37324282

RESUMO

We have applied the sensitize-train-hack-community model to build awareness of and capacity in bioinformatics in Kenya. Open science is the practice of science openly and collaboratively, with tools, techniques, and data freely shared to facilitate reuse and collaboration. Open science is not a mandatory curriculum course in schools, whereas bioinformatics is relatively new in some African regions. Open science tools can significantly enhance bioinformatics, leading to increased reproducibility. However, open science and bioinformatics skills, especially blended, are still lacking among students and researchers in resource-constrained regions. We note the need to be aware of the power of open science among the bioinformatics community and a clear strategy to learn bioinformatics and open science skills for use in research. Using the OpenScienceKE framework-Sensitize, Train, Hack, Collaborate/Community-the BOSS (Bioinformatics and Open Science Skills) virtual events built awareness and empowered researchers with the skills and tools in open science and bioinformatics. Sensitization was achieved through a symposium, training through a workshop and train-the-trainer program, hack through mini-projects, community through conferences, and continuous meet-ups. In this paper, we discuss how we applied the framework during the BOSS events and highlight lessons learnt in planning and executing the events and their impact on the outcome of each phase. We evaluate the impact of the events through anonymous surveys. We show that sensitizing and empowering researchers with the skills works best when the participants apply the skills to real-world problems: project-based learning. Furthermore, we have demonstrated how to implement virtual events in resource-constrained settings by providing Internet and equipment support to participants, thus improving accessibility and diversity.

13.
J Toxicol ; 2023: 7058016, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37854041

RESUMO

Sodium metabisulfite (SMB) is a biocide and antioxidant agent generally used as a preservative in food and beverage industries but can oxidize to harmful sulfite radicals. A standardized Ginkgo biloba (EGb-761) has demonstrated potent antioxidant and anti-inflammatory activities, which is beneficial for the treatment of diseases that exhibit oxidative stress and inflammation. The present study sought to investigate the putative ameliorative effects of EGb-761 against SMB-induced toxicity in mice. Thirty-two male Swiss white mice were randomized into control, SMB-treated, SMB + EGb-761-treated, and EGb-761-treated groups. EGb-761 (100 mg/kg/day) and SMB (98 mg/kg/day) were administered by gastric gavage for 40 days. Oral administration of EGb-761 restored SMB-induced decrease in body weight and prevented SMB-induced thrombocytopenia, leukocytosis, and anemia. Furthermore, EGb-761-treatment protected against SMB-induced liver and kidney injury depicted by decreased serum levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase, bilirubin, creatinine, urea, uric acid, and albumin. Furthermore, EGb-761 treatment attenuated SMB-driven dyslipidemia and metabolic acidosis. Besides, EGb-761 supplementation abrogated SMB-driven oxidative stress as depicted by stabilized reduced glutathione (GSH) levels in the brain, liver, kidney, spleen, heart, and lungs. SMB induced a significant increase of tissue levels of malondialdehyde (MDA), serum nitric oxide (NO), interferon-gamma (IFN-γ) and tumor necrosis factor-α (TNF-α) which were abrogated by EGb-761 treatment. In conclusion, these results deepen our understanding of EGb-761 in light of various detrimental effects of SMB-driven toxicities. These findings provide a novel approach that can be optimized for preventing or treating exposure due to SMB toxicity.

14.
Parasitol Int ; 96: 102775, 2023 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-37390918

RESUMO

Infection with Trypanosoma brucei rhodesiense (T.b.r) causes acute Human African Trypanosomiasis (HAT) in Africa. This study determined the effect of vitamin B12 on T.b.r -driven pathological events in a mouse model. Mice were randomly assigned into four groups; group one was the control. Group two was infected with T.b.r; group three was supplemented with 8 mg/kg vitamin B12 for two weeks; before infection with T.b.r. For group four, administration of vitamin B12 was started from the 4th days post-infection with T.b.r. At 40 days post-infection, the mice were sacrificed to obtain blood, tissues, and organs for various analyses. The results showed that vitamin B12 administration enhanced the survival rate of T.b.r infected mice, and prevented T.b.r-induced disruption of the blood-brain barrier and decline in neurological performance. Notably, T.b.r-induced hematological alteration leading to anaemia, leukocytosis and dyslipidemia was alleviated by vitamin B12. T.b.r-induced elevation of the liver alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase and total bilirubin as well as the kidney damage markers urea, uric acid and creatinine were attenuated by vitamin B12. Vitamin B12 blocked T.b.r-driven rise in TNF-α and IFN-γ, nitric oxide and malondialdehyde. T.b.r-induced depletion of GSH levels were attenuated in the presence of vitamin B12 in the brain, spleen and liver tissues; a clear indication of the antioxidant activity of vitamin B12. In conclusion, treatment with vitamin B12 potentially protects against various pathological events associated with severe late-stage HAT and presents a great opportunity for further scrutiny to develop an adjunct therapy for severe late-stage HAT.


Assuntos
Trypanosoma brucei brucei , Tripanossomíase Africana , Animais , Camundongos , Barreira Hematoencefálica/patologia , Modelos Animais de Doenças , Óxido Nítrico , Trypanosoma brucei rhodesiense , Tripanossomíase Africana/tratamento farmacológico , Vitamina B 12/efeitos adversos
15.
NPJ 2D Mater Appl ; 7(1): 12, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-38665486

RESUMO

The development of high-precision large-area optical coatings and devices comprising low-dimensional materials hinges on scalable solution-based manufacturability with control over exfoliation procedure-dependent effects. As such, it is critical to understand the influence of technique-induced transition metal dichalcogenide (TMDC) optical properties that impact the design, performance, and integration of advanced optical coatings and devices. Here, we examine the optical properties of semiconducting MoS2 films from the exfoliation formulations of four prominent approaches: solvent-mediated exfoliation, chemical exfoliation with phase reconversion, redox exfoliation, and native redox exfoliation. The resulting MoS2 films exhibit distinct refractive indices (n), extinction coefficients (k), dielectric functions (ε1 and ε2), and absorption coefficients (α). For example, a large index contrast of Δn ≈ 2.3 is observed. These exfoliation procedures and related chemistries produce different exfoliated flake dimensions, chemical impurities, carrier doping, and lattice strain that influence the resulting optical properties. First-principles calculations further confirm the impact of lattice defects and doping characteristics on MoS2 optical properties. Overall, incomplete phase reconfiguration (from 1T to mixed crystalline 2H and amorphous phases), lattice vacancies, intraflake strain, and Mo oxidation largely contribute to the observed differences in the reported MoS2 optical properties. These findings highlight the need for controlled technique-induced effects as well as the opportunity for continued development of, and improvement to, liquid phase exfoliation methodologies. Such chemical and processing-induced effects present compelling routes to engineer exfoliated TMDC optical properties toward the development of next-generation high-performance mirrors, narrow bandpass filters, and wavelength-tailored absorbers.

16.
J Phys Chem Lett ; 13(25): 5808-5814, 2022 Jun 30.
Artigo em Inglês | MEDLINE | ID: mdl-35726902

RESUMO

Two-dimensional (2D) transition metal dichalcogenides (TMDCs) exhibit compelling dimension-dependent exciton-dominated optical behavior influenced by thickness and lateral quantum confinement effects. Thickness quantum confinement effects have been observed; however, experimental optical property assessment of nanoscale lateral dimension monolayer TMDCs is lacking. Here, we employ ex situ spectroscopic ellipsometry to evaluate laterally coalescing monolayer metalorganic chemical vapor deposited MoS2. A multisample analysis is used to constrain Bruggeman and Maxwell-Garnett effective medium approximations and the effective dielectric functions are derived for laterally coalesced and uncoalesced MoS2 films (∼10-94% surface coverage for ∼10-140 nm lateral grain sizes). This analysis demonstrates the ability to probe MoS2 optical exciton behavior at growth-relevant grain sizes in relation to chemical vapor nucleation density, ripening, and lateral growth conditions. Our analysis is pertinent toward expected in situ epitaxial 2D TMDC film growth metrology to enable the facile development of monolayer films with targeted process-dependent optical properties.

17.
ACS Nano ; 15(1): 21-28, 2021 Jan 26.
Artigo em Inglês | MEDLINE | ID: mdl-33356122

RESUMO

Achieving excellent electromagnetic interference (EMI) shielding combined with mechanical flexibility, optical transparency, and environmental stability is vital for the future of coatings, electrostatic discharge, electronic displays, and wearable and portable electronic devices. Unfortunately, it is challenging to engineer materials with all of these desired properties due to a lack of understanding of the underlying materials physics and structure-property relationships. Nature has provided numerous examples of a combination of properties through precision engineering of hierarchical structures at multiple length scales with selectively chosen ingredients. This inspiration is reflected in a wide range of synthetic architected nanocomposites. In this Perspective, we provide a brief overview of recent advances in the role of hierarchical architectures in MXene-based thin-film nanocomposites in the quest to achieve multiple functionalities, especially focusing on a combination of excellent EMI shielding, transparency, and mechanical robustness. We also discuss key opportunities, challenges, and prospects.

18.
ACS Nano ; 15(2): 2771-2777, 2021 Feb 23.
Artigo em Inglês | MEDLINE | ID: mdl-33502839

RESUMO

The versatile property suite of two-dimensional MXenes is driving interest in various applications, including energy storage, electromagnetic shielding, and conductive coatings. Conventionally, MXenes are synthesized by a wet-chemical etching of the parent MAX-phase in HF-containing media. The acute toxicity of HF hinders scale-up, and competing surface hydrolysis challenges control of surface composition and grafting methods. Herein, we present an efficient, room-temperature etching method that utilizes halogens (Br2, I2, ICl, IBr) in anhydrous media to synthesize MXenes from Ti3AlC2. A radical-mediated process depends strongly on the molar ratio of the halogen to MAX phase, absolute concentration of the halogen, the solvent, and temperature. This etching method provides opportunities for controlled surface chemistries to modulate MXene properties.

19.
Parasit Vectors ; 14(1): 74, 2021 Jan 22.
Artigo em Inglês | MEDLINE | ID: mdl-33482903

RESUMO

BACKGROUND: Trypanosoma brucei species are motile protozoan parasites that are cyclically transmitted by tsetse fly (genus Glossina) causing human sleeping sickness and nagana in livestock in sub-Saharan Africa. African trypanosomes display digenetic life cycle stages in the tsetse fly vector and in their mammalian host. Experimental work on insect-stage trypanosomes is challenging because of the difficulty in setting up successful in vitro cultures. Therefore, there is limited knowledge on the trypanosome biology during its development in the tsetse fly. Consequently, this limits the development of new strategies for blocking parasite transmission in the tsetse fly. METHODS: In this study, RNA-Seq data of insect-stage trypanosomes were used to construct a T. brucei gene co-expression network using the weighted gene co-expression analysis (WGCNA) method. The study identified significant enriched modules for genes that play key roles during the parasite's development in tsetse fly. Furthermore, potential 3' untranslated region (UTR) regulatory elements for genes that clustered in the same module were identified using the Finding Informative Regulatory Elements (FIRE) tool. RESULTS: A fraction of gene modules (12 out of 27 modules) in the constructed network were found to be enriched in functional roles associated with the cell division, protein biosynthesis, mitochondrion, and cell surface. Additionally, 12 hub genes encoding proteins such as RNA-binding protein 6 (RBP6), arginine kinase 1 (AK1), brucei alanine-rich protein (BARP), among others, were identified for the 12 significantly enriched gene modules. In addition, the potential regulatory elements located in the 3' untranslated regions of genes within the same module were predicted. CONCLUSIONS: The constructed gene co-expression network provides a useful resource for network-based data mining to identify candidate genes for functional studies. This will enhance understanding of the molecular mechanisms that underlie important biological processes during parasite's development in tsetse fly. Ultimately, these findings will be key in the identification of potential molecular targets for disease control.


Assuntos
Perfilação da Expressão Gênica , Redes Reguladoras de Genes , Insetos Vetores/parasitologia , Proteínas de Protozoários/genética , Trypanosoma brucei brucei/genética , Moscas Tsé-Tsé/parasitologia , Animais , Estágios do Ciclo de Vida/genética
20.
Front Cell Infect Microbiol ; 11: 774537, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34869075

RESUMO

Introduction: Naturally acquired immune responses against antigens expressed on the surface of mature gametocytes develop in individuals living in malaria-endemic areas. Evidence suggests that such anti-gametocyte immunity can block the development of the parasite in the mosquito, thus playing a role in interrupting transmission. A better comprehension of naturally acquired immunity to these gametocyte antigens can aid the development of transmission-blocking vaccines and improve our understanding of the human infectious reservoir. Methods: Antigens expressed on the surface of mature gametocytes that had not previously been widely studied for evidence of naturally acquired immunity were identified for protein expression alongside Pfs230-C using either the mammalian HEK293E or the wheat germ cell-free expression systems. Where there was sequence variation in the candidate antigens (3D7 vs a clinical isolate PfKE04), both variants were expressed. ELISA was used to assess antibody responses against these antigens, as well as against crude stage V gametocyte extract (GE) and AMA1 using archived plasma samples from individuals recruited to participate in malaria cohort studies. We analyzed antibody levels (estimated from optical density units using a standardized ELISA) and seroprevalence (defined as antibody levels greater than three standard deviations above the mean levels of a pool of malaria naïve sera). We described the dynamics of antibody responses to these antigens by identifying factors predictive of antibody levels using linear regression models. Results: Of the 25 antigens selected, seven antigens were produced successfully as recombinant proteins, with one variant antigen, giving a total of eight proteins for evaluation. Antibodies to the candidate antigens were detectable in the study population (N = 216), with seroprevalence ranging from 37.0% (95% CI: 30.6%, 43.9%) for PSOP1 to 77.8% (95% CI: 71.6%, 83.1%) for G377 (3D7 variant). Responses to AMA1 and GE were more prevalent than those to the gametocyte proteins at 87.9% (95% CI: 82.8%, 91.9%) and 88.3% (95% CI: 83.1%, 92.4%), respectively. Additionally, both antibody levels and breadth of antibody responses were associated with age and concurrent parasitaemia. Conclusion: Age and concurrent parasitaemia remain important determinants of naturally acquired immunity to gametocyte antigens. Furthermore, we identify novel candidates for transmission-blocking activity evaluation.


Assuntos
Malária Falciparum , Animais , Anticorpos Antiprotozoários , Formação de Anticorpos , Antígenos de Protozoários , Humanos , Plasmodium falciparum , Proteínas de Protozoários/genética , Estudos Soroepidemiológicos
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