CB - DBF - Artigos publicados em periódicos

URI Permanente para esta coleçãohttps://repositorio.ufrn.br/handle/1/104

Navegar

Agora exibindo 1 - 20 de 99

3R and 2H polytypes of MoS2: DFT and DFPT calculations of structural, optoelectronic, vibrational and thermodynamic properties
(Elsevier, 2017-12) Coutinho, S.S.; Barboza, Carlos Antonio; Tavares, M.S.; Frazão, N.F.; Moreira, E.; Azevedo, David L.
We report the results of a theoretical study on the behavior of the structural, optoelectronic, vibrational, including infrared and Raman theoretical spectra, phonon spectrum, and thermodynamic properties of 3R- and 2H- polytypes of molybdenum disulfide (MoS2) using density functional theory (DFT) considering both the local density and generalized gradient approximation, LDA and GGA, respectively. Calculated lattice parameters are close to the experimental measurements, and an indirect band gap E(A→KΓ)¼ 1:33 eV (0.68 eV) was obtained within the GGA (LDA) level of calculation, considering the 3R-polytype, and for the 2H- polytype an indirect band gap E(Γ→KΓ)¼ 1:30 eV (0.70 eV) was obtained within the GGA (LDA) approximation. The complex dielectric function and absorption of 3R-MoS2 and 2H-MoS2 polytypes were shown to be sensitive to the plane of polarization of the incident light. The phonon dispersion relation together with density of states (DOS) as well as theoretical peaks of the infrared (IR) and Raman spectra in the frequency range of 0–800 cm 1 was analyzed and assigned, considering the norm-conserved pseudopotentials. The thermodynamic potentials, the specific heat at constant volume and Debye temperature of the 3R-MoS2 and 2H-MoS2 polytypes are also calculated, whose dependence on the temperature are discussed.
Opioid neurotransmission modulates defensive behavior and fear-induced antinociception in dangerous environments
(Elsevier, 2017-06-23) Coimbra, Norberto Cysne; Soares, Bruno Lobão; Calvo, Fabrício; Almada, Rafael Carvalho; Freitas, Renato Leonardo; Paschoalin-Maurin, Tatiana; Anjos-Garcia, Tayllon dos; Elias-Filho, Daoud Hibrahim; Ubiali, Walter Adriano; Tracey, Irene
The effects of endogenous opioid peptide antagonists on panic-related responses are controversial. Using elevated mazes and a prey-versus-predator paradigm, we investigated the involvement of the endogenous opioid peptide-mediated system in the modulation of anxiety- and panic attack-induced responses and innate fear-induced antinociception in the present work. Wistar rats were intraperitoneally pretreated with either physiological saline or naloxone at different doses and were subjected to either the elevated plus- or T-maze test or confronted by Crotalus durissus terrificus. The defensive behaviors of the rats were recorded in the presence of the predator and at 24 h after the confrontation, when the animals were placed in the experimental enclosure without the rattlesnake. The peripheral non-specific blockade of opioid receptors had a clear anxiolytic-like effect on the rats subjected to the elevated plus-maze but not on those subjected to the elevated T-maze; however, a clear panicolytic-like effect was observed, i.e., the defensive behaviors decreased, and the prey-versus-predator interaction responses evoked by the presence of the rattlesnakes increased. A similar effect was noted when the rats were exposed to the experimental context in the absence of the venomous snake. After completing all tests, the naloxone-treated groups exhibited less anxiety/fear-induced antinociception than the control group, as measured by the tail-flick test. These findings demonstrate the anxiolytic and panicolytic-like effects of opioid receptor blockade. In addition, the fearlessness behavior displayed by preys treated with naloxone at higher doses enhanced the defensive behavioral responses of venomous snakes.
Lithium and valproate prevent methylphenidate-induced mania-like behaviors in the hole board test
(Elsevier, 2016-08-26) Souza, L.S.; Soares, Bruno Lobão; Silva, E.F.; Santos, W.B.; Asth, L.; Soares-Rachetti, V.P.; Medeiros, I.U.; Gavioli, E.C.
Manic bipolar is diagnosed by psychomotor agitation, increased goal-directed activity, insomnia, grandiosity, excessive speech, and risky behavior. Animal studies aimed to modeling mania are commonly based in psychostimulants-induced hyperlocomotion. The exploration of other behaviors related with mania is mandatory to investigate this phase of bipolar disorder in animals. In this study, the hole board apparatus was suggested for evaluating mania-like behaviors induced by the psychostimulant methylphenidate. The treatment with methylphenidate (10 mg/kg, ip) increased locomotion in the open field test. The pretreatment with lithium (50 mg/kg, ip) and valproate (400 mg/kg, ip) significantly prevented the hyperlocomotion. In the hole-board test, methylphenidate increased interactions with the central and peripheral holes and the exploration of central areas. Lithium was more effective than valproate in preventing all the behavioral manifestations induced by the psychostimulant. These findings were discussed based on the ability of methylphenidate-treated mice mimicking two symptoms of mania in the hole board test: goal-directed action and risk-taking behavior. In conclusion, the results point to a new approach to study mania through the hole board apparatus. The hole board test appears to be a sensitive assay to detect the efficacy of antimanic drugs.
Nitroprusside single-dose prevents the psychosis-like behavior induced by ketamine in rats for up to one week
(Elsevier, 2015-03) Maia-de-Oliveira, Joao Paulo; Soares, Bruno Lobão; Ramalho, Thais; Gavioli, Elaine C.; Soares, Vanessa Paula; Teixeira, Leslie; Baker, Glen B.; Dursun, Serdar M.; Hallak, Jaime E.C.
Recently, we found a rapid and long-lasting improvement of symptoms in schizophrenic patients on antipsychotics after a single four-hour infusion of sodium nitroprusside (SNP), a nitric oxide (NO) donor with a short half-life. This improvement persisted for up to 4 weeks. Because these patients remained on antipsychotics after infusion of SNP was finished, the question arises about whether this improvement was due to SNP itself. We have now investigated whether SNP, alone, can produce preventive antipsychotic effects in rats treated with ketamine (KET). 56 adult rats divided into 7 groups were infused with SNP 4 mg/kg, KET 25 mg/kg, or saline as follows: group1 — saline, group2 — SNP, group3 — KET, group4 — KET 12 h after SNP, group5 — KET 1 day after SNP, group6 — KET 2 days after SNP, and group7 — KET 1 week after SNP. The animals were filmed in an open field arena for 30 min and the videos were later analyzed by ANY-Maze software to measure activity and stereotypy. SNP significantly prevented the emergence of hyperactivity induced by KET when it was administered for up to 1 week before KET, and prevented the emergence of stereotypies when it was administered for up to 1 day before KET. These findings in rats, which have an even faster metabolic rate than humans, suggest that the long-lasting effects observed in our clinical trial with SNP in humans could have been due to SNP itself, and indicate for the first time that SNP may present preventive antipsychotic effects.
There is more to the picture than meets the rat: A study on rodent geometric shape and proportion preferences
(Elsevier, 2015-05-01) Winne, Jéssica; Teixeira, Leslie; Pessoa, Jéssica de Andrade; Gavioli, Elaine Cristina; Rachetti, Vanessa Soares; André, Eunice; Soares, Bruno Lobão
In rodents, the novel object preference test has been used as a behavioral parameter for evaluation of neotic exploratory behavior, and also for memory consolidation tasks. Geometric patterns of this preference are poorly understood, and may vary among species. We evaluated in Wistar rats (Rattus norvergicus) a possible exploration preference considering aluminum tripartite rounded and cylindrical objects of different proportions: 1.2; 1.618; 1.8. At the first day, animals were exposed to 1.2; 1.6 and 1.8 rounded objects. At 24 h after, these animals were exposed to the same objects, together with three new steel cylindrical objects (same proportions). ANOVA and T tests were used to quantify object exploration for each animal (p < 0.05). Data analysis pointed to a longer exploration time of the object 1.2 at the three different protocols indicating a preference pattern on the first day exposition. On the second day the exploration was similar in both familiar and unfamiliar objects, revealing no novel object preference for cylinders. However, we found an object preference related to the 1.2 proportion (balls plus cylinders), in two of three position protocols. In addition, on a single exposition with both cylinders and rounded objects, rats revealed a rounded object preference. The 1.2 preference disclosed by rats also reflected the proportion of their body. From nine main measures of body ratios, seven were close to 1.2 ratio. The correspondence between body ratios and object preference may be explained by habituation learning and by sexual selection, and highlight innate factors regarding aesthetic preferences among species.
Nociceptin/orphanin FQ induces simultaneously anxiolytic and amnesic effects in the mouse elevated T-maze task
(Springer, 2014-10-16) Asth, Laila; Correia, Nataly; Soares, Bruno Lobão; Lima, Thereza C. Monteiro de; Guerrini, Remo; Calo', Girolamo; Soares-Rachetti, Vanessa P.; Gavioli, Elaine C.
Studies have shown a close relationship between anxiety and aversive memory processing, but few animal models are suitable for investigating the effects of a given compound on anxiety and memory simultaneously. A growing body of evidence suggests anxiolytic and amnesic effects of nociceptin/orphanin FQ (N/OFQ). The mouse elevated Tmaze (ETM) has been shown to detect the effects of drugs on anxiety and memory at the same time. In this study, the effects of intracerebroventricular N/OFQ injected before or immediately after training session were assessed in the ETM task. When pretraining injected, N/OFQ 0.1 nmol significantly decreased the latency to enter an open arm in the training session compared to control, which is suggestive of anxiolysis. In addition, N/OFQ (0.1 and 1 nmol) significantly reduced the latency to enter an open arm during the test session compared to control, thus suggesting memory impairments. However, when N/OFQ was administered posttraining, it did not affect memory retrieval. No alterations in locomotion were detected in N/OFQ-treated mice in the open field test. In conclusion, these findings are discussed considering the simultaneous anxiolytic and amnesic effects of N/OFQ.
The elevated T-maze task as an animal model to simultaneously investigate the effects of drugs on long-term memory and anxiety in mice
(Elsevier, 2012-04-10) Soares, Bruno Lobão; Asth, Laila; André, Eunice; Soares, Vanessa de Paula; Gavioli, Elaine Cristina
The elevated T-maze (ETM) is an apparatus derived from the elevated plus-maze test, which is used to evaluate anxiety. Because anxiety is a biasing factor in models of memory, this study proposed the ETM as a task for the simultaneous assessment of memory and anxiety in mice. The ETM consists of one enclosed and two open arms. The procedure is based on the avoidance of open spaces learned during training session, in which mice were exposed to the enclosed arm as many times as needed to stay 300 s. In the test session, memory is assessed by re-exposing the mouse to the enclosed arm and the latency to enter an open arm was recorded. The anxiolytic diazepam (DZP; 1 or 2 mg/kg) and the amnestic biperiden (BPR; 0.5, 1 or 3 mg/kg) were injected at three distinct times: pre-training, post-training, and pre-test. Pretraining administration of BPR 1 and DZP 2 increased the number of trials needed to reach the avoidance criterion, suggesting a passive avoidance learning impairment. However, BPR induced hyperlocomotion, which could bias the interpretation of any BPR-induced effects during the training session. Pre-training injection of BPR did not affect the spontaneous increase in the latency to enter an open arm between trials, while DZP reduced latencies in the first three trials suggesting anxiolysis. In the test session, pre-training injection of BPR 1 and DZP 2 reduced latencies to enter an open arm, indicating memory impairment. Post-training and pre-test injection of DZP or BPR did not affect memory. In conclusion, the proposed ETM task is practical for the detection of the anxiolytic and amnesic effects of drugs.
LDA vs QDA for FT-MIR prostate cancer tissue classification
(Elsevier, 2017-03-15) Araújo, Aurigena Antunes de; Siqueira, Laurinda F.S.; Araújo Júnior, Raimundo F.; Morais, Camilo L.M.; Lima, Kássio M.G.
Discrimination/classification of biological material a ta molecular level is one of the key aims of chemometrics applied to biospectroscopic data. Two discriminant functions, namely Linear Discriminant Analysis (LDA) and Quadratic Discriminant Analysis (QDA), were considered in this study for prostate cancer classification based on FT-MIR data, and illustrated graphically as boundary methods. Principal Component Analysis (PCA) was applied as a variable/dimensionality reduction method and Genetic Algorithm (GA) as variable selection method, followed by LDA and QDA. The performance of each method was determined using 40–100 MIR spectra per tissue sample (n=45), previously classified according to Gleason traditional grading by pathologists. The methods were used to separate the two-category of prostate cancer: Low grade (Gleason grade 2) vs. High grade (Gleason grade 3 and 4). The models were optimized using a training set and their performance was evaluated using a test set. Classification rates and quality metrics (Sensitivity, Specificity, Positive (or Precision) and Negative Predictive Values, Youden's index, and Positive and Negative Likelihood Ratios) were computed for each model. QDA-based models obtained higher classification rates and quality performance than LDA-based models. The models studied identify that secondary protein structure variations and DNA/RNA alterations are the main biomolecular ‘difference markers’ for prostate cancer grades.
Photodynamic therapy using chloro-aluminum phthalocyanine decreases inflammatory response in an experimental rat periodontal disease model
(Elsevier, 2017-02) Araujo, Aurigena Antunes; Moraes, Maiara de; Vasconcelos, Roseane Carvalho; Longo, João Paulo Figueiró; Muehlmann, Luis Alexandre; Azevedo, Ricardo Bentes de; Araújo Júnior, Raimundo Fernandes de; Costa, Antonio de Lisboa Lopes
Background and Objective Emerging evidence suggests that photodynamic therapy (PDT) can exhibit immunomodulatory activity. The purpose of the present study was to analyse cytokine profiles after application of PDT in gingival tissues of rats with ligature-induced periodontal disease (PD). Study Design/Material and Methods Periodontal disease was induced through the introduction of a cotton thread around the first left mandibular molar, while the right side molars did not receive ligatures. After 7 days of PD evolution, ligatures were removed from the left side, and the animals were randomically divided into the following treatment groups: I, rats without treatment; II, rats received chloro-aluminum phthalocyanine (AlClPc); III, rats received low-level laser alone; and IV, rats received AlClPc associated with low-level laser (PDT). The animals were killed 7 days after the treatments, and the mandibles were histologically processed to assess morphological and immunohistochemical profile, while gingival tissues were removed for quantification of tumor necrosis factor (TNF)-α, interleukin (IL-)1β and IL-10 expression (by ELISA). Results Histomorphological analysis of periodontal tissues demonstrated that PDT-treated animals show tissue necrosis, as well as lower TNF- α expression, compared to ligatured animals treated with AlClPc alone. Conclusions It was concluded that PDT using AlClPc entrapped in a lipid nanoemulsion may be useful in therapies, because of immunomodulatory effects that decreased the inflammatory response and cause tissue destruction.
Effect of Dexamethasone-Loaded PLGA Nanoparticles on Oral Mucositis Induced by 5-Fluorouracil
(MDPI, 2021-01-04) Ribeiro, Susana Barbosa; Araújo, Aurigena Antunes de; Oliveira, Maisie Mitchele Barbosa; Silva, Alaine Maria dos Santos; Silva Júnior, Arnóbio Antônio da; Guerra, Gerlane Coelho Bernardo; Brito, Gerly Anne de Castro; Leitão, Renata Ferreira de Carvalho; Araújo Júnior, Raimundo Fernandes de; Garcia, Vinícius Barreto; Vasconcelos, Roseane Carvalho; Medeiros, Caroline Addison Carvalho Xavier de
Oral mucositis (OM) is characterized by the presence of severe ulcers in the oral region that affects patients treated with chemotherapy. It occurs in almost all patients who receive radiotherapy of the head and neck, as well as patients who undergo hematopoietic cell transplantation. The pathophysiology of OM is complex, and there is no effective therapy. The aim of this study was to evaluate the effect of dexamethasone-loaded poly(D,L-Lactic-co-glycolic) nanoparticles (PLGA-DEX NPs) on an OM model induced in hamsters. The NPs were synthesized using the emulsification-solvent evaporation method and were characterized by the size, zeta potential, encapsulation efficiency, atomic force microscopy, physicochemical stability, and the in vitro release. The OM was induced by the administration of 5-FU on the first and second days and mechanical trauma on the 4th day of the experiment. PLGA-DEX NPs were administered to treat OM. The animals were euthanized on the 10th day. Macroscopic and histopathological analyses were performed, measurement of malonaldehyde (MDA) and ELISA was used to determine the levels of IL-1β and TNF-α. Immunoexpressions of NF-κB, COX-2, and TGF-β were determined by immunohistochemistry, and qRT-PCR was used to quantify the gene expression of the GILZ, MKP1, and NF-κB p65. The PLGA-DEX NPs (0.1 mg/kg) significantly reduced macroscopic and histopathological scores, decreased MDA, TNF-α and IL-1β levels, immunostaining for NF-κB, COX-2, TGF-β, and suppressed NF-κB p65 mRNA expression, but increased GILZ and MKP1 expression
Injectable platelet rich fibrin: cell content, morphological, and protein characterization
(Springer Science and Business Media LLC, 2018-07-12) Nascimento, Rubens Maribondo do; Varela, Hugo Almeida; Souza, Júlio C. M.; Araújo Júnior, Raimundo Fernandes de; Vasconcelos, Roseane Carvalho; Cavalcante, Rômulo dos Santos; Guedes, Paulo Marcos Matta; Araújo, Aurigena Antunes
Objectives The aim of the present study was to evaluate the blood cell content, morphological aspects, gene expression of type I collagen, and release of growth factors on an injectable platelet rich fibrin (i-PRF). Materials and methods Blood samples were collected from 15 volunteers to prepare i-PRF samples. Peripheral blood was used as a control group. Blood clot and i-PRF samples were cultured for 10 days. The supernatant of the samples was collected for ELISA immunoassay quantification of PDGF and VEGF growth factors over periods of 1, 8, 24, 72, and 240 h. I-PRF and blood clot samples were biologically characterized using histological and immunohistochemistry analysis for IL-10, osteocalcin, and TGF-β. Scanning electron microscopy (SEM) was used to inspect the fibrin network and distribution of blood platelets and leukocytes. Reverse transcriptase polymerase chain reaction (RT-PCR) method was used to evaluate gene expression for type I collagen. Results A higher concentration of platelets and lymphocytes was recorded in i-PRF than in peripheral blood (p < 0.05). The release of VEGF was higher in blood clot samples (1933 ± 704) than that for i-PRF (852 ± 376; p < 0.001). Immunohistochemistry showed upregulation of TGF-B, IL-10, and osteocalcin in the i-PRF group. RT-PCR showed increased type I collagen gene expression in i-PRF (p < 0.05). SEM images revealed agglomeration of platelets in some regions, while a fibrin networking was noticeable in the entire i-PRF sample. Conclusions Injectable platelet rich fibrin becomes a good approach for soft and mineralized tissue healing considering the formation of a three-dimensional fibrin network embedding platelets, leukocytes, type I collagen, osteocalcin, and growth factors. Indeed, the injectable platelet rich fibrin can be indicated in several medical applications regarding bioactivity, simplied technique, and flowable mixing with other biomaterials. Clinical relevance Morphological, cell, and protein characterization of platelet rich fibrin provides a better understanding of the clinical effects and improvement of clinical guidelines for several medical applications. Once well physicochemical and biologically characterized, the use of an injectable platelet rich fibrin can be extended to other applications in the field of orthopedics, periodontics, and implant dentistry on the repairing process of both soft and mineralized tissues
Zirconia/hydroxyapatite (80/20) scaffold repair in critical size calvarial defect increased FGF-2, osteocalcin and OPG immunostaining and IL-10 levels
(American Journal of Translational Research, 2020-01-15) Vasconcelos, Roseane Carvalho; Ferreira, Camyla; Araújo, Eduarda Medeiros de; Motta, Fabiana Villela da; Delmonte, Mauricio Roberto Bomio; Araújo Júnior, Raimundo Fernandes de; Paiva, Daniel Felipe Fernandes; Pirih, Flavia Q.; Silva, José Sandro Pereira da; Chan, Alan B.; Cruz, Luis J.; Ishii, Makiko; Medeiros, Caroline Addison Carvalho Xavier de; Guerra, Gerlane Coelho Bernardo; Araújo, Aurigena Antunes de
The aim of this study was to characterize and evaluate zirconia/hydroxyapatite in a critical size calvarial defect model in rats. Zirconia/hydroxyapatite (80/20) scaffold was characterized by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). Critical size (8 mm) calvarial defects were created in wistar rats (n=48) and divided into four groups (90 days): G0 Group: positive control; G1 Group: hydroxyapatite; G2 Group: Zirconia; G3 Group: Zirconia/hydroxyapatite (80/20). Calvaria were subjected to Micro CT, histological and immunohistochemical analyses (RANK, RANKL, OPG, osteocalcin and FGF-2). IL-1 beta, IL-10 and TNF-alpha levels were analyzed by Elisa Immunoassay. The XRD analysis confirmed the formation of a crystalline structure and SEM showed the presence of regions corresponding to Zirconia and Hydroxyapatite. The Micro CT showed increased bone volume (BV/TV) and bone mineral density (BMD) in the G3 group (P<0.05). In addition, discrete periosteal bone formation was found at the interface of the defect edge and the external surface of the scaffold in the G3 group, showing osteocytes inside and osteoblasts (P<0.05) with scarce mononuclear inflammatory cells (P<0.01) in the central region of the defect. The immunostaining was moderate for RANKL, Osteocalcin and FGF-2 in the G3 group (P<0.5), while it was intense for OPG (P<0.001). IL-1 beta levels were decreased and IL-10 levels increased (P<0.05). Zirconia/hydroxyapatite (80/20) scaffold repair in critical size calvarial defects increased bone density, osteoblast and osteoclast cell numbers, FGF-2, osteocalcin and OPG immunostaining and IL-10 levels
Evaluation of the antiproliferative activity of 2-amino thiophene derivatives against human cancer cells lines
(Elsevier, 2016-12) Aguiar, Andreza Conception Véras de; Moura, Ricardo Olímpio de; Mendonça Junior, Jaime Francisco Bezerra; Rocha, Hugo Alexandre de Oliveira; Câmara, Rafael Barros Gomes da; Schiavon, Manuela dos Santos Carvalho
In spite of great progress in understanding cancer biology, current therapeutic procedures remain unsatisfactory. Chemotherapy is often followed by secondary effects with cellular toxicity negatively affecting the results. The discovery and development of new safe and efficient antitumor agents is necessary. Derivatives of 2-amino thiophene have been a topic of constant investigation due to their versatile synthetic applicability and broad spectrum of biological applications; among which are antifungal and antiproliferative activity shown in prior studies of our group. In the current study, compounds 6CN09, 6CN10, 6CN12, 6CN14, 7CN09 and 7CN11 were analyzed as to antiproliferative effect in human cells of cervical adenocarcinoma (HeLa), human pancreatic adenocarcinoma (PANC-1) and mice fibroblasts (3T3), which were exposed to the compounds in concentrations of 5, 10, 25 and 50mM during 24 and 48 h. They were submitted to MTT assay. In order to elucidate the action mechanism of antitumor thiophene derivatives flow cytometry was performed to evaluate cell death and cell cycle analysis. The results showed that thiophene derivatives demonstrated great antiproliferative potential in the HeLa and PANC-1 cell lines when compared with the control, and the percentage of cell proliferation inhibition approximated or was higher than the standard drug used; doxorubicin (Dox). In highlight were the derivatives 6CN14 and 7CN09 that showed greater efficiency in the antiproliferative evaluation. Further, all compounds had a protective effect on the non-tumor 3T3 cell line. The flow cytometry analysis showed few cells in apoptosis in both the HeLa and PANC-1 lines, although the compounds interfered with the progression of the cell cycle, and avoided cell growth and multiplication in the HeLa tumor line. These thiophene derivatives demonstrated cytostatic and antiproliferative effects and may be considered as promising molecular candidates for anticancer drugs
Charge transport in fibrous/not fibrous -helical and variant peptides
(American Institute of Physics, 2011-01-31) Bezerril, Leonardo Mafra; Fulco, Umberto Laino; Oliveira, Jonas Ivan Nobre; Corso, Gilberto; Albuquerque, Eudenilson Lins de; Freire, V. N.; Caetano, W. S.
Although differing only by the Ala→Gln substitution at the fifth or seventh position of the 3-peptide amino acid sequence Leu-Glu-Thr-Leu-Ala-Lys-Ala3, the 5Q3 variant forms fibrous assemblies more attenuated than those of the 3-peptide, while the 7Q3 variant does not form fibrils. A tight-binding transport modeling was performed to obtain their current-voltage patterns, with hopping energies of the dipeptides calculated within the density functional theory framework. Beyond the semiconductor character, we obtain that the current pattern can be used to distinguish them, suggesting that it can be useful for the development of devices as diagnostics tools for amyloidosislike diseases
Electronic specific heat of an a3-helical polypeptide and its biochemical variants
(Elsevier, 2012-07-23) Bezerril, Leonardo Mafra; Mendes, G. A.; Albuquerque, Eudenilson Lins de; Fulco, Umberto Laico; Caetano, E. W. S.; Freire, V. N.
We perform a theoretical study of the temperature dependent electronic specific heat at constant volume CV ðTÞ for a fibrous a3-helical polypeptide, which has the amino acid sequence (Leu-Glu-Thr-Leu-Ala-Lys- Ala)3, considering only its primary structure. We focus also on two different variants of the a3-helical polypeptide, namely those with (5Qa3 variant, mutation Ala5Gln) and without (7Qa3 variant, mutation Ala7Gln) fibrous assemblies. The energy spectra are calculated using a two-dimensional Schrödinger equation within a tight-binding approximation in which the isolated amino acid vertical ionization energy and the hopping terms are found using density functional theory computations
Molecular modelling and quantum biochemistry computations of a naturally occurring bioremediation enzyme: Alkane hydroxylase from Pseudomonas putida P1
(Elsevier, 2017-10) Sousa, Bruno Gomes de; Oliveira, Jonas Ivan Nobre; Albuquerque, Eudenilson Lins de; Fulco, Umberto Laico; Amaro, Venerando Eustáquio; Blaha, Carlos Alfredo Galindo
Many species of bacteria involved in degradation of n-alkanes have an important constitutional metabolic enzyme, the alkane hydroxylase called AlkB, specialized in the conversion of hydrocarbons molecules that can be used as carbon and/or energy source. This enzyme plays an important role in the microbial degradation of oil, chlorinated hydrocarbons, fuel additives, and many other compounds. A number of these enzymes has been biochemically characterized in detail because the potential of alkane hydroxylases to catalyse high added-value reactions is widely recognized. Nevertheless, the industrial and process bioremediation application of them is restricted, owing to their complex biochemistry, challenging process requirements, and the limited number of their three-dimensional structures. Furthermore, AlkB has great potential as biocatalysts for selective transformation of a wide range of chemically inert unreactive alkanes into reactive chemical precursors that can be used as tools for bioremediation and bioprocesses. Aiming to understand the possible ways the AlkB enzyme Pseudomonas putida P1 interacts with octane, octanol and 1-octyne, we consider its suitable biochemical structure taking into account a 3-D homology modelling. Besides, by using a quantum chemistry computational model based on the density functional theory (DFT), we determine possible protein-substrate interaction regions measured by means of its binding energy simulated throughout the Molecular Fractionation with Conjugated Caps (MFCC) approach
Quantifying entropy using recurrence matrix microstates
(American Institute of Physics, 2018-08-09) Corso, Gilberto; Prado, Thiago de Lima; Lima, Gustavo Zampier dos Santos; Kurths, Jürgen; Lopes, Sérgio Roberto
We conceive a new recurrence quantifier for time series based on the concept of information entropy, in which the probabilities are associated with the presence of microstates defined on the recurrence matrix as small binary submatrices. The new methodology to compute the entropy of a time series has advantages compared to the traditional entropies defined in the literature, namely, a good correlation with the maximum Lyapunov exponent of the system and a weak dependence on the vicinity threshold parameter. Furthermore, the new method works adequately even for small segments of data, bringing consistent results for short and long time series. In a case where long time series are available, the new methodology can be employed to obtain high precision results since it does not demand large computational times related to the analysis of the entire time series or recurrence matrices, as is the case of other traditional entropy quantifiers. The method is applied to discrete and continuous systems
Optimizing the detection of nonstationary signals by using recurrence analysis
(American Institute of Physics, 2018-08-24) Prado, Thiago de Lima; Lima, Gustavo Zampier dos Santos; Lobão-Soares, Bruno; Nascimento, George Carlos do; Corso, Gilberto; Araújo, John Fontenele; Kurths, Jürgen; Lopes, Sérgio Roberto
Recurrence analysis and its quantifiers are strongly dependent on the evaluation of the vicinity threshold parameter, i.e., the threshold to regard two points close enough in phase space to be considered as just one. We develop a new way to optimize the evaluation of the vicinity threshold in order to assure a higher level of sensitivity to recurrence quantifiers to allow the detection of even small changes in the dynamics. It is used to promote recurrence analysis as a tool to detect nonstationary behavior of time signals or space profiles. We show that the ability to detect small changes provides information about the present status of the physical process responsible to generate the signal and offers mechanisms to predict future states. Here, a higher sensitive recurrence analysis is proposed as a precursor, a tool to predict near future states of a particular system, based on just (experimentally) obtained signals of some available variables of the system. Comparisons with traditional methods of recurrence analysis show that the optimization method developed here is more sensitive to small variations occurring in a signal. The method is applied to numerically generated time series as well as experimental data from physiology
Hippocampal and cortical communication around micro-arousals in slow-wave sleep
(Nature Publishing Group, 2019-04-10) Lima, Gustavo Zampier dos Santos; Lobão-Soares, Bruno; Corso, Gilberto; Belchior, Hindiael Aeraf; Lopes, Sergio Roberto Lopes; Prado, Thiago de Lima; Nascimento, George Carlos do; Araújo, John Fontenele; Ivanov, Plamen Ch.
Sleep plays a crucial role in the regulation of body homeostasis and rhythmicity in mammals. Recently, a specific component of the sleep structure has been proposed as part of its homeostatic mechanism, named micro-arousal. Here, we studied the unique progression of the dynamic behavior of cortical and hippocampal local field potentials (LFPs) during slow-wave sleep-related to motor-bursts (micro-arousals) in mice. Our main results comprised: (i) an abrupt drop in hippocampal LFP amplitude preceding micro-arousals which persisted until the end of motor-bursts (we defined as t interval, around 4s) and a similar, but delayed amplitude reduction in cortical (S1/M1) LFP activity occurring at micro-arousal onset; (ii) two abrupt frequency jumps in hippocampal LFP activity: from Theta (6–12 Hz) to Delta (2–4 Hz), also t seconds before the micro-arousal onset, and followed by another frequency jump from Delta to Theta range (5–7 Hz), now occurring at micro-arousal onset; (iii) a pattern of cortico-hippocampal frequency communication precedes micro-arousals: the analysis between hippocampal and cortical LFP fluctuations reveal high coherence during τ interval in a broader frequency band (2–12 Hz), while at a lower frequency band (0.5–2 Hz) the coherence reaches its maximum after the onset of micro-arousals. In conclusion, these novel findings indicate that oscillatory dynamics pattern of cortical and hippocampal LFPs preceding micro-arousals could be part of the regulatory processes in sleep architecture
Waiting-time statistics in magnetic systems
(Nature Research, 2020-06-16) Sousa, Ivandson Praeiro de; Lima, Gustavo Zampier dos Santos; Corrêa, Marcio Assolin; Sommer, Rubem Luis; Corso, Gilberto; Bohn, Felipe
Many complex systems, from earthquakes and financial markets to Barkhausen effect in ferromagnetic materials, respond with a noise consisting of discrete avalanche-like events with broad range of sizes and durations, separated by waiting times. Here we focus on the waiting-time statistics in magnetic systems. By investigating the Barkhausen noise in amorphous and polycrystalline ferromagnetic films having different thicknesses, we uncover the form of the waiting-time distribution in time series recorded from the irregular and irreversible motion of magnetic domain walls. Further, we address the question of if the waiting-time distribution evolves with the threshold level, as well as with the film thickness and structural character of the materials. Our results, besides informing on the temporal avalanche correlations, disclose the waiting-time statistics in magnetic systems also bring fingerprints of the universality classes of Barkhausen avalanches and a dimensional crossover in the domain wall dynamics

SIGAA

Navegar

Submissões Recentes