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1.
J Chem Phys ; 159(4)2023 Jul 28.
Artigo em Inglês | MEDLINE | ID: mdl-37486052

RESUMO

In this research, we explore sequence-dependent chiral-induced spin selectivity (CISS) in double-stranded (ds)-DNA using time-correlated single-photon counting and electrochemical impedance spectroscopy supplemented by tight-binding calculations of the phenomenon for the first time. The average lifetime of the photo-excited electrons in a Quantum Dot-DNA system is influenced by the CISS effect generated by the DNA molecule, and the difference in average time decay of electrons was found to be 345 ps for opposite polarity ("UP" and "DOWN") of spins due to the CISS effect. Moreover, the yield of spin-polarized electrons due to the CISS effect was reduced by more than 35% from perfect DNA to DNA with point mutations. Remarkably, by employing a tight binding method combined with Green's function formalism for transport, simulations of the process support the observed experimental trends. Our results provide a basic understanding of the sequence-specific spin-dependent electron transfer through ds-DNA. These results would help to build spin-based next-generation DNA sensors.


Assuntos
Pontos Quânticos , Transporte de Elétrons , DNA/química , Elétrons
2.
J Chem Phys ; 159(2)2023 Jul 14.
Artigo em Inglês | MEDLINE | ID: mdl-37449581

RESUMO

We address the electron-spin-phonon coupling in an effective model Hamiltonian for DNA to assess its role in spin transfer involved in the Chiral-Induced Spin Selectivity (CISS) effect. The envelope function approach is used to describe semiclassical electron transfer in a tight-binding model of DNA at half filling in the presence of intrinsic spin-orbit coupling. Spin-phonon coupling arises from the orbital-configuration dependence of the spin-orbit interaction. We find spin-phonon coupling only for the acoustic modes, while the optical modes exhibit electron-phonon interaction without coupling to spin. We derive an effective Hamiltonian whose eigenstates carry spin currents that are protected by spin-inactive stretching optical modes. As optical phonons interact more strongly than acoustic phonons, side buckling and tilting optical base modes will be more strongly associated with decoherence, which allows for the two terminal spin filtering effects found in CISS.


Assuntos
DNA , Fônons , Transporte de Elétrons , Elétrons
3.
J Chem Phys ; 159(22)2023 Dec 14.
Artigo em Inglês | MEDLINE | ID: mdl-38063226

RESUMO

We analyze from a theoretical perspective recent experiments where chiral discrimination in biological systems was established using Atomic Force Microscopy (AFM). Even though intermolecular forces involved in AFM measurements have different origins, i.e., electrostatic, bonding, exchange, and multipole interactions, the key molecular forces involved in enantiospecific biorecognition are electronic spin exchange and van der Waals (vdW) dispersion forces, which are sensitive to spin-orbit interaction (SOI) and space-inversion symmetry breaking in chiral molecules. The vdW contribution to chiral discrimination emerges from the inclusion of SOI and spin fluctuations due to the chiral-induced selectivity effect, a result we have recently demonstrated theoretically. Considering these two enantiospecific contributions, we show that the AFM results regarding chiral recognition can be understood in terms of a simple physical model that describes the different adhesion forces associated with different electron spin polarization generated in the (DD), (LL), and (DL) enantiomeric pairs, as arising from the spin part of the exchange and vdW contributions. The model can successfully produce physically reasonable parameters accounting for the vdW and exchange interaction strength, accounting for the chiral discrimination effect. This fact has profound implications in biorecognition where the relevant intermolecular interactions in the intermediate-distance regime are clearly connected to vdW forces.

4.
Vascular ; : 17085381231193453, 2023 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-37526918

RESUMO

OBJECTIVES: Several predictive models exist for estimating the postoperative risks of abdominal aortic aneurysm (AAA) repair, although no particular tool has seen widespread use. We present the results of a multicenter, historic cohort study comparing the predictive capacity of the psoas muscle area (PMA), radiodensity (PMD), and lean muscle area (LMA) as surrogate markers of sarcopenia, over short- and long-term outcomes after AAA repair, compared to the mFI-5 and American Society of Anesthesiologists (ASA) scales. METHODS: Retrospective review was conducted of all consecutive AAA elective repair cases (open or endovascular) in three tertiary-care centers from 2014 to 2019. Cross-sectional PMA, PMD, and LMA at the mid-body of the L3 vertebra were measured by two independent operators in the preoperative computed tomography. Receiver operating characteristic (ROC) curves were used to determine optimal cutoff values. Bivariate analysis, logistic regression, and Cox's proportional hazards models were built to examine the relationship between baseline variables and postoperative mortality, long-term mortality, and complications. RESULTS: 596 patients were included (mean age 72.7 ± 8 years, 95.1% male, 66.9% EVAR). Perioperative mortality was 2.3% (EVAR 1.2% vs open repair 4.6%, p = .015), and no independent predictors could be identified in the multivariate analysis. Conversely, an age over 74 years old (OR 1.84 95%CI 1.25-2.70), previous heart diseases (OR 1.62 95%CI 1.13-2.32), diabetes mellitus (OR 1.61 95%CI 1.13-2.32), and a PMD value over 66 HU (OR 0.58 95%CI 0.39-0.84) acted as independent predictors of long-term mortality in the Cox's proportional hazards model. Heart diseases (congestive heart failure or coronary artery disease), serum creatinine levels over 1.05 mg/dL, and an aneurysm diameter over 60 mm were independent predictors of major complications. CONCLUSION: Surrogate markers of sarcopenia had a poor predictive profile for postoperative mortality after AAA repair in our sample. However, PMD stood out as an independent predictor of long-term mortality. This finding can guide future research and should be confirmed in larger datasets.

5.
Angew Chem Int Ed Engl ; 62(16): e202218767, 2023 Apr 11.
Artigo em Inglês | MEDLINE | ID: mdl-36752105

RESUMO

By employing a mechanically controllable break junction technique, we have realized an ideal single molecular linear actuator based on dithienylethene (DTE) based molecular architecture, which undergoes reversible photothermal isomerization when subjected to UV irradiation under ambient conditions. As a result, open form (compressed, UV OFF) and closed form (elongated, UV ON) of dithienylethene-based molecular junctions are achieved. Interestingly, the mechanical actuation is achieved without changing the conductance of the molecular junction around the Fermi level over several cycles, which is an essential property required for an ideal single molecular actuator. Our study demonstrates a unique example of achieving a perfect balance between tunneling width and barrier height change upon photothermal isomerization, resulting in no change in conductance but a change in the molecular length, which results in mechanical actuation at the single molecular level.

6.
J Neurosci ; 40(24): 4661-4672, 2020 06 10.
Artigo em Inglês | MEDLINE | ID: mdl-32393538

RESUMO

It is widely assumed that electrical synapses in the mammalian brain, especially between interneurons, underlie neuronal synchrony. In the hippocampus, principal cells also establish electrical synapses with each other and have also been implicated in network oscillations, whereby the origin of fast electrical activity has been attributed to ectopic spikelets and dendro-dendritic or axo-axonal gap junctions. However, if electrical synapses were in axo-dendritic connections, where chemical synapses occur, the synaptic events would be mixed, having an electrical component preceding the chemical one. This type of communication is less well studied, mainly because it is not easily detected. Moreover, a possible scenario could be that an electrical synapse coexisted with a chemical one, but in a nonconductive state; hence, it would be considered inexistent. Could chemical synapses have a quiescent electrical component? If so, can silent electrical synapses be activated to be detected? We addressed this possibility, and we here report that, indeed, the connexin-36-containing glutamatergic mossy fiber synapses of the rat hippocampus express previously unrecognized electrical synapses, which are normally silent. We reveal that these synapses are pH sensitive, actuate in vitro and in vivo, and that the electrical signaling is bidirectional. With the simultaneous recording of hundreds of cells, we could reveal the existence of an electrical circuit in the hippocampus of adult rats of either sex consisting of principal cells where the nodes are interregional glutamatergic synapses containing silent but ready-to-use gap junctions.SIGNIFICANCE STATEMENT In this work, we present a series of experiments, both in vitro and in vivo, that reveal previously unrecognized silent pH-sensitive electrical synapses coexisting in one of the best studied glutamatergic synapses of the brain, the mossy fiber synapse of the hippocampus. This type of connectivity underlies an "electrical circuit" between two substructures of the adult rat hippocampus consisting of principal cells where the nodes are glutamatergic synapses containing silent but ready-to-use gap junctions. Its identification will allow us to explore the participation of such a circuit in physiological and pathophysiological functions and will provide valuable conceptual tools to understanding computational and regulatory mechanisms that may underlie network activity.


Assuntos
Sinapses Elétricas/fisiologia , Junções Comunicantes/fisiologia , Ácido Glutâmico/metabolismo , Hipocampo/fisiologia , Rede Nervosa/fisiologia , Neurônios/fisiologia , Transmissão Sináptica/fisiologia , Animais , Células Cultivadas , Sinapses Elétricas/metabolismo , Junções Comunicantes/metabolismo , Hipocampo/metabolismo , Masculino , Rede Nervosa/metabolismo , Neurônios/metabolismo , Ratos , Ratos Sprague-Dawley , Ratos Wistar
7.
Nano Lett ; 20(10): 7077-7086, 2020 10 14.
Artigo em Inglês | MEDLINE | ID: mdl-32786950

RESUMO

The physical origin of the so-called chirality-induced spin selectivity (CISS) effect has puzzled experimental and theoretical researchers over the past few years. Early experiments were interpreted in terms of unconventional spin-orbit interactions mediated by the helical geometry. However, more recent experimental studies have clearly revealed that electronic exchange interactions also play a key role in the magnetic response of chiral molecules in singlet states. In this investigation, we use spin-polarized closed-shell density functional theory calculations to address the influence of exchange contributions to the interaction between helical molecules as well as of helical molecules with magnetized substrates. We show that exchange effects result in differences in the interaction properties with magnetized surfaces, shedding light into the possible origin of two recent important experimental results: enantiomer separation and magnetic exchange force microscopy with AFM tips functionalized with helical peptides.

8.
Rev Esp Enferm Dig ; 113(12): 851-852, 2021 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-34470451

RESUMO

A 58-year-old, otherwise healthy male presented to the Emergency Room due to a 24-hour-long bloody diarrhea and constitutional syndrome. Colonoscopy confirmed the presence of a colonic neoplasia. A CT scan revealed an irregular surface and poorly delimited hypodensity of liver segment 5, next to the neoplasia, with malignant infiltration being impossible to rule out.


Assuntos
Neoplasias do Colo , Colo/diagnóstico por imagem , Neoplasias do Colo/diagnóstico por imagem , Neoplasias do Colo/patologia , Colonoscopia , Humanos , Fígado/patologia , Masculino , Pessoa de Meia-Idade , Tomografia Computadorizada por Raios X , Ultrassonografia
9.
Entropy (Basel) ; 23(9)2021 Sep 04.
Artigo em Inglês | MEDLINE | ID: mdl-34573791

RESUMO

Living cells are complex systems characterized by fluids crowded by hundreds of different elements, including, in particular, a high density of polymers. They are an excellent and challenging laboratory to study exotic emerging physical phenomena, where entropic forces emerge from the organization processes of many-body interactions. The competition between microscopic and entropic forces may generate complex behaviors, such as phase transitions, which living cells may use to accomplish their functions. In the era of big data, where biological information abounds, but general principles and precise understanding of the microscopic interactions is scarce, entropy methods may offer significant information. In this work, we developed a model where a complex thermodynamic equilibrium resulted from the competition between an effective electrostatic short-range interaction and the entropic forces emerging in a fluid crowded by different sized polymers. The target audience for this article are interdisciplinary researchers in complex systems, particularly in thermodynamics and biophysics modeling.

10.
Langmuir ; 36(39): 11600-11609, 2020 10 06.
Artigo em Inglês | MEDLINE | ID: mdl-32924496

RESUMO

The investigation of molecular interactions between silica phases and organic components is crucial for elucidating the main steps involved in the biosilica mineralization process. In this respect, the structural characterization of the organic/inorganic interface is particularly useful for a deeper understanding of the dominant mechanisms of biomineralization. In this work, we have investigated the interaction of selectively 13C- and 15N-labeled atoms of organic long-chain polyamines (LCPAs) with 29Si-labeled atoms of a silica layer at the molecular level. In particular, silica/LCPA nanocomposites were analyzed by solid-state NMR spectroscopy in combination with all-atom molecular dynamics simulations. Solid-state NMR experiments allow the determination of 29Si-15N and 29Si-13C internuclear distances, providing the parameters for direct verification of atomistic simulations. Our results elucidate the relevant molecular conformations as well as the nature of the interaction between the LCPA and a silica substrate. Specifically, distances and second moments suggest a picture compatible with (i) LCPA completely embedded in the silica phase and (ii) the charged amino groups located in close vicinity of silanol groups.

11.
Transpl Infect Dis ; 22(6): e13432, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32738811

RESUMO

PURPOSE: The study's aim was to assess whether polyomavirus DNAemia screening was associated with different outcomes in patients with positive viremia compared with negative viremia. METHODS: Case-control retrospective study of patients with polyomavirus DNAemia (viremia > 1000 copies/mL) matched 1:1 with controls. Control group consists of the patient who received a transplant immediately before or after each identified case and did have nil viremia. FINDING: Ultimately, 120 cases of BK polyomavirus (BKPyV) were detected and matched with 130 controls. Of these, 54 were adult kidney transplant recipients (KTRs), 43 were pediatric KTRs, and 23 were undergoing hemato-oncologic therapy, of which 20 were undergoing hematopoietic stem cell transplantation. The odds ratio (OR) for overall risk of poorer outcomes in cases versus controls was 16.07 (95% CI: 5.55-46.54). The unfavorable outcome of switching the immunosuppressive drug (ISD) (14/40,35%) was no different from that of those treated with reduced ISD doses (31/71, 43.6%, P = .250). Acute rejection or graft-versus-host disease, previous transplant, and intensity of immunosuppression (4 ISDs plus induction or conditioning) were risk factors for BKPyV-DNAemia (OR: 13.96, 95% CI: 11.25-15.18, P < .001; OR: 6.14, 95% CI: 3.91-8.80, P < .001; OR: 5.53, 95% CI: 3.37-7.30, P < .001, respectively). CONCLUSIONS: Despite viremia screening, dose reduction, and change in therapeutic protocol, patients with positive BKPyV-DNAemia present poorer outcomes and unfavorable results.


Assuntos
Transplante de Células-Tronco Hematopoéticas , Transplante de Rim , Infecções por Polyomavirus , Infecções Tumorais por Vírus , Viremia/classificação , Adulto , Vírus BK , Estudos de Casos e Controles , Criança , Rejeição de Enxerto , Doença Enxerto-Hospedeiro , Humanos , Infecções por Polyomavirus/complicações , Estudos Retrospectivos , Fatores de Risco , Infecções Tumorais por Vírus/complicações
12.
J Chem Phys ; 152(21): 214105, 2020 Jun 07.
Artigo em Inglês | MEDLINE | ID: mdl-32505170

RESUMO

The chirality-induced spin selectivity effect has been confirmed experimentally for a large class of organic molecules. Adequately modeling the effect remains a challenging task, with both phenomenological models and first-principles simulations yielding inconclusive results. Building upon a previously presented model by K. Michaeli and R. Naaman [J. Phys. Chem. C 123, 17043 (2019)], we systematically investigate an effective 1-dimensional model derived as the limit of a 3-dimensional quantum system with strong confinement and including spin-orbit coupling. Having a simple analytic structure, such models can be considered a minimal setup for the description of spin-dependent effects. We use adiabatic perturbation theory to provide a mathematically sound approximation procedure applicable to a large class of spin-dependent continuum models. We take advantage of the simplicity of the models by analyzing its structure to gain a better understanding how the occurrence and magnitude of spin polarization effects relate to the model's parameters and geometry. The obtained spin polarization is not strongly dependent on the strength of the spin-orbit interaction, but it rather results from breaking time-reversal invariance upon selection of a given angular momentum of the incoming electrons.

13.
Int J Mol Sci ; 21(20)2020 Oct 10.
Artigo em Inglês | MEDLINE | ID: mdl-33050466

RESUMO

Amyloid-beta oligomers (AßO) have been proposed as the most potent neurotoxic and inflammation inducers in Alzheimer's disease (AD). AßO contribute to AD pathogenesis by impairing the production of several cytokines and inflammation-related signaling pathways, such as the Janus kinases/signal transducer of transcription factor-3 (JAK/STAT3) pathway. STAT3 modulates glial activation, indirectly regulates Aß deposition, and induces cognitive decline in AD transgenic models. However, in vivo studies using an AßO microinjection rat model have not yet explored STAT3 role. The main purpose of this study was to elucidate if a single microinjection of AßO could promote an increased expression of STAT3 in glial cells favoring neuroinflammation and neurodegeneration. We designed a model of intrahippocampal microinjection and assessed glial activation, cytokines production, STAT3 expression, and neurodegeneration in time. Our results showed robust expression of STAT3 in glial cells (mainly in astrocytes) and neurons, correlating with neuronal death in response to AßO administration. A STAT3 inhibition assay conducted in rat primary hippocampal cultures, suggested that the induction of the transcription factor by AßO in astrocytes leads them to an activation state that may favor neuronal death. Notwithstanding, pharmacological inhibition of the JAK2/STAT3 pathway should be focused on astrocytes because it is also essential in neurons survival. Overall, these findings strongly suggest the participation of STAT3 in the development of neurodegeneration.


Assuntos
Peptídeos beta-Amiloides/metabolismo , Astrócitos/metabolismo , Gliose/etiologia , Gliose/metabolismo , Neurônios/metabolismo , Fator de Transcrição STAT3/metabolismo , Doença de Alzheimer/etiologia , Doença de Alzheimer/metabolismo , Doença de Alzheimer/patologia , Animais , Astrócitos/patologia , Biomarcadores , Morte Celular , Modelos Animais de Doenças , Suscetibilidade a Doenças , Imunofluorescência , Gliose/patologia , Hipocampo/metabolismo , Hipocampo/patologia , Imuno-Histoquímica , Agregados Proteicos , Agregação Patológica de Proteínas/genética , Agregação Patológica de Proteínas/metabolismo , Multimerização Proteica , Ratos , Fator de Transcrição STAT3/genética
14.
J Neurosci ; 38(42): 9034-9046, 2018 10 17.
Artigo em Inglês | MEDLINE | ID: mdl-30190413

RESUMO

Fast ripples (FRs; activity of >250 Hz) have been considered as a biomarker of epileptic activity in the hippocampus and entorhinal cortex; it is thought that they signal the focus of seizure generation. Similar high-frequency network activity has been produced in vitro by changing extracellular medium composition, by using pro-epileptic substances, or by electrical stimulation. Here we study the propagation of these events between different subregions of the male rat hippocampus in a recently introduced experimental model of FRs in entorhinal cortex-hippocampal slices in vitro By using a matrix of 4096 microelectrodes, the sites of initiation, propagation pathways, and spatiotemporal characteristics of activity patterns could be studied with unprecedented high resolution. To this end, we developed an analytic tool based on bidimensional current source density estimation, which delimits sinks and sources with a high precision and evaluates their trajectories using the concept of center of mass. With this methodology, we found that FRs can arise almost simultaneously at noncontiguous sites in the CA3-to-CA1 direction, underlying the spatial heterogeneity of epileptogenic foci, while continuous somatodendritic waves of activity develop. An unexpected, yet important propagation route is the propagation of activity from CA3 into the hilus and dentate gyrus. This pathway may cause reverberating activation of both regions, supporting sustained pathological network events and altered information processing in hippocampal networks.SIGNIFICANCE STATEMENT Fast ripples (FRs) have been considered as a biomarker of epileptic activity and may signal the focus of seizure generation. In a model of traumatic brain injury in the rat, FRs appear in the hippocampus within a couple of hours after an extrahippocampal, cortical lesion. We analyzed the origin and dynamics of the FRs in the hippocampus using massive electrophysiological recordings, allowing an unprecedented high spatiotemporal resolution. We show that FRs originate in distinct and noncontiguous locations within the CA3 region and uncover, with high precision, the extent and dynamics of their current density. This activity propagates toward CA1 but also backpropagates to the hilus and the dentate gyrus, suggesting activation of defined microcircuits that can sustain recurrent excitation.


Assuntos
Lesões Encefálicas Traumáticas/fisiopatologia , Ondas Encefálicas , Córtex Entorrinal/fisiopatologia , Epilepsia/fisiopatologia , Hipocampo/fisiopatologia , Neurônios/fisiologia , Animais , Lesões Encefálicas Traumáticas/complicações , Modelos Animais de Doenças , Epilepsia/etiologia , Masculino , Vias Neurais/fisiopatologia , Ratos Wistar
15.
Langmuir ; 35(8): 2997-3004, 2019 Feb 26.
Artigo em Inglês | MEDLINE | ID: mdl-30707589

RESUMO

The ability to tune the electronic properties of oxide-bearing semiconductors such as Si/SiO2 or transparent metal oxides such as indium-tin oxide (ITO) is of great importance in both electronic and optoelectronic device applications. In this work, we describe a process that was conducted on n-type Si/SiO2 and ITO to induce changes in the substrate work function (WF). The substrates were modified by a two-step synthesis comprising a covalent attachment of coupling agents' monolayer followed by in situ anchoring reactions of polarizable chromophores. The coupling agents and chromophores were chosen with opposite dipole orientations, which enabled the tunability of the substrates' WF. In the first step, two coupling agents with opposite molecular dipole were assembled. The coupling agent with a negative dipole induced a decrease in WF of modified substrates, while the coupling agent with a positive dipole produced an increase in WFs of both ITO and Si substrates. The second modification step consisted of in situ anchoring reaction of polarizable chromophores with opposite dipoles to the coupling layer. This modification led to an additional change in the WFs of both Si/SiO2 and ITO substrates. The WF was measured by contact potential difference and modeled by density functional theory-based theoretical calculations of the WF for each of the assembly steps. A good fit was obtained between the calculated and experimental trends. This ability to design and tune the WF of ITO substrates was implemented in an organic electronic device with improved I- V characteristics in comparison to a bare ITO-based device.

16.
Langmuir ; 35(34): 11114-11122, 2019 08 27.
Artigo em Inglês | MEDLINE | ID: mdl-31361147

RESUMO

Peptides are very common recognition entities that are usually attached to surfaces using multistep processes. These processes require modification of the native peptides and of the substrates. Using functional groups in native peptides for their assembly on surfaces without affecting their biological activity can facilitate the preparation of biosensors. Herein, we present a simple single-step formation of native oxytocin monolayer on gold surface. These surfaces were characterized by atomic force spectroscopy, spectroscopic ellipsometry, and X-ray photoelectron spectroscopy. We took advantage of the native disulfide bridge of the oxytocin for anchoring the peptide to the Au surface, while preserving the metal-ion binding properties. Self-assembled oxytocin monolayer was used by electrochemical impedance spectroscopy for metal-ion sensing leading to subnanomolar sensitivities for zinc or copper ions.

17.
Phys Chem Chem Phys ; 21(4): 1904-1911, 2019 Jan 23.
Artigo em Inglês | MEDLINE | ID: mdl-30632565

RESUMO

BNC heteronanotubes are promising materials for the design of nanoscale thermoelectric devices. In particular, the structural BN doping pattern can be exploited to control the electrical and thermal transport properties of BNC nanostructures. We here address the thermoelectric transport properties of (6,6)-BNC heteronanotubes with helical and horizontal BN doping patterns. For this, we use a density functional tight-binding method combined with the Green's function technique. Our results show that the electron transmission is reduced and the electronic bandgap increased as a function of the BN concentration for different doping distribution patterns, so that (6,6)-BNC heteronanotubes become semiconducting with a tunable bandgap. The thermal conductance of helical (6,6)-BNC heteronanotubes, which is dominated by phonons, is weakly dependent on BN concentration in the range of 30-80%. Also, the Seebeck coefficient is enhanced by increasing the concentration of helical BN strips. In particular, helical (6,6)-BNC heteronanotubes with a high BN concentration (>20%) display a larger figure of merit compared to other doping distributions and, for a concentration of 50%, reach values up to 2.3 times and 3.4 times the corresponding values of a CNT at 300 K and 800 K, respectively. Our study yields new insights into the parameters tuning the thermoelectric efficiency and thus provides a starting point for designing thermoelectric devices based on BNC nanostructures.

18.
Phytother Res ; 33(3): 591-601, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-30488503

RESUMO

Osteosarcoma (OSA) is a type of bone cancer showing an aggressive biological behavior with metastatic progression. Because propolis potential for the development of new antitumoral drugs has been indicated, we evaluated the chemical composition of Colombian propolis samples and the mechanisms involved in their cytotoxic effects on OSA cells. The chemical composition was analyzed by GC-MS and the DPPH free radical scavenging activity was measured. Cluster and principal components analysis were used to establish an association with their inhibitory concentration 50% (IC50 ). Cell viability was analyzed by MTT assay; apoptosis was determined by flow cytometry; mitochondrial membrane permeability and reactive oxygen species were evaluated by rhodamine 123 and DCFH-DA. Transwell assay was used to evaluate the invasiveness of propolis-treated cells. Samples were grouped: Cluster 1 contained diterpenes and benzophenones and showed the highest antiradical activity; Cluster 2 was characterized by triterpenes, fatty acid, and diterpenes. Usm contained diterpenes and triterpenes different of the other samples and Sil contained triterpenes and flavonoids. Apoptosis, mitochondrial membrane alteration, and suppression of cell invasion were the main mechanisms involved in the inhibition of OSA cells in vitro, suggesting the potential of Colombian propolis to discover new antitumor drugs.


Assuntos
Apoptose/efeitos dos fármacos , Neoplasias Ósseas/patologia , Osteossarcoma/patologia , Própole/química , Própole/farmacologia , Animais , Antioxidantes/química , Antioxidantes/farmacologia , Neoplasias Ósseas/metabolismo , Sobrevivência Celular/efeitos dos fármacos , Colômbia , Citotoxinas/química , Citotoxinas/farmacologia , Diterpenos/química , Diterpenos/farmacologia , Doenças do Cão/metabolismo , Doenças do Cão/patologia , Cães , Flavonoides/química , Flavonoides/farmacologia , Cromatografia Gasosa-Espectrometria de Massas , Osteossarcoma/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Transdução de Sinais/efeitos dos fármacos , Triterpenos/química , Triterpenos/farmacologia , Células Tumorais Cultivadas
19.
Entropy (Basel) ; 21(8)2019 Jul 27.
Artigo em Inglês | MEDLINE | ID: mdl-33267449

RESUMO

A crucial goal for increasing thermal energy harvesting will be to progress towards atomistic design strategies for smart nanodevices and nanomaterials. This requires the combination of computationally efficient atomistic methodologies with quantum transport based approaches. Here, we review our recent work on this problem, by presenting selected applications of the PHONON tool to the description of phonon transport in nanostructured materials. The PHONON tool is a module developed as part of the Density-Functional Tight-Binding (DFTB) software platform. We discuss the anisotropic phonon band structure of selected puckered two-dimensional materials, helical and horizontal doping effects in the phonon thermal conductivity of boron nitride-carbon heteronanotubes, phonon filtering in molecular junctions, and a novel computational methodology to investigate time-dependent phonon transport at the atomistic level. These examples illustrate the versatility of our implementation of phonon transport in combination with density functional-based methods to address specific nanoscale functionalities, thus potentially allowing for designing novel thermal devices.

20.
J Neurosci ; 37(3): 701-714, 2017 01 18.
Artigo em Inglês | MEDLINE | ID: mdl-28100750

RESUMO

The mossy fibers (MFs) corelease glutamate and GABA onto pyramidal cells of CA3 during development, until the end of the third postnatal week. However, the major target cells of the MF are the interneurons of CA3. Therefore, it has been shown that the interneurons of the hilus and stratum lucidum receive this dual monosynaptic input on MF stimulation. Because the plasticity of glutamatergic transmission from the different terminals of the MF is target specific, we here asked whether the corelease of glutamate and GABA was also subjected to a target-dependent compartmentalization. We analyzed the occurrence and plasticity of MF simultaneous glutamatergic-GABAergic signaling onto interneurons of the different strata of CA3 in rats during the third postnatal week. We show the coexistence of time-locked, glutamate receptor and GABA receptor-mediated mono synaptic responses evoked by MF stimulation in interneurons from stratum lucidum and stratum radiatum, but not in interneurons from stratum lacunosum-moleculare. As expected from the transmission of MF origin, MF GABAergic responses were depressed by the activation of metabotropic glutamate receptors. Strikingly, while MF glutamatergic responses underwent LTD, the simultaneous MF GABAergic responses of stratum lucidum interneurons, but not of stratum radiatum interneurons, displayed a Hebbian form of LTP that was mimicked by PKC activation. PKA activation potentiated MF glutamatergic responses of stratum radiatum interneurons, whereas in stratum lucidum interneurons only GABAergic responses were potentiated. We here disclose that the corelease of glutamate and GABA, as well as their plasticity are compartmentalized in a target-dependent manner, showing counterbalanced compensatory plasticity of two neurotransmitters released by different terminals of the same pathway. SIGNIFICANCE STATEMENT: The mossy fibers transiently corelease glutamate and GABA onto pyramidal cells of CA3. We here describe that they can also corelease these amino acids onto interneurons, in a target-dependent manner. Many interneurons in stratum lucidum and stratum radiatum receive both signals, while those in stratum lacunosum-moleculare exclusively receive a glutamatergic signal. It is noteworthy that glutamatergic LTD, which is known to exist on stratum lucidum interneurons, coexists in the same pathway with a presynaptic form of GABAergic LTP, while interneurons of stratum radiatum, despite receiving this dual signaling, do not display such plasticity. The GABAergic LTP is mimicked with PKA or PKC activation. We disclose compartmentalized corelease of glutamate and GABA and its differential plasticity from a single pathway onto different interneuron sets.


Assuntos
Ácido Glutâmico/metabolismo , Interneurônios/metabolismo , Fibras Musgosas Hipocampais/metabolismo , Ácido gama-Aminobutírico/metabolismo , Potenciais de Ação/fisiologia , Animais , Masculino , Técnicas de Cultura de Órgãos , Ratos , Ratos Wistar
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