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1.
Int J Biol Macromol ; 154: 142-149, 2020 Mar 14.
Artigo em Inglês | MEDLINE | ID: mdl-32184141

RESUMO

Clozapine is an atypical antipsychotic used for the treatment of schizophrenia. The prescribed target daily doses may reach 900 mg. Literature studies report a connection between clozapine usage and thrombosis development. Our in vitro study aimed to provide insight into molecular bases of this observation, investigating clozapine binding to fibrinogen, the main plasma protein involved in hemostasis. Fibrinogen/clozapine interaction was confirmed by protein fluorescence quenching, with an affinity constant of 1.7 × 105 M-1. Direct interactions did not affect the structure of fibrinogen, nor fibrinogen melting temperature. Clozapine binding affected fibrin formation by reducing coagulation speed and thickness of fibrin fibers suggesting that in the presence of clozapine, fibrinogen may acquire thrombogenic characteristics. Although no difference in fibrin gel porosity was detected, other factors present in the blood may act synergistically with altered fibrin formation to modify fibrin clot, thus increasing the risk for development of thrombosis in patients on clozapine treatment. ORAC and HORAC assays showed that clozapine reduced free radical-induced oxidation of fibrinogen. All observed effects of clozapine on fibrinogen are dose-dependent, with the effect on fibrin formation being more pronounced.

2.
Clin Oral Investig ; 24(1): 141-150, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31053896

RESUMO

OBJECTIVES: The aims of this study were (i) to assess cumulative survival rates of class II resin-based composite and compomer restorations in primary molars with a 5-year observation period and (ii) to analyze the influence of different types of anesthesia and different localizations of the restorations in the teeth. METHODS: Patient charts of a private practice for pediatric dentistry were screened for class II resin-based composite (Spectrum TPH3) and compomer (Dyract Posterior; both Dentsply DeTrey) restorations in primary molars with a 5-year observation period used with Adper Prompt L-Pop (3M-ESPE). One restoration per patient (age ≤ 6 years at placement) was randomly selected. RESULTS: Two hundred sixty restorations were included (43% resin-based composites, 57% compomers). After 5 years, cumulative survival rates were 43% for resin-based composite and 49% for compomer restorations with no statistically significant differences. There was a tendency for higher survival rates for restorations placed under N2O inhalation sedation or general anesthesia. Distal-occlusal compomer restorations showed significantly lower survival rates (p = 0.003) as compared to mesial-occlusal compomer restorations. CONCLUSION: Within the limitations of the study, we conclude that type of restorative material as well as the type of anesthesia do not influence restoration survival rates, although restorations placed in patients receiving N2O inhalation sedation or general anesthesia tend to perform better as compared with patients receiving no anesthesia or only local infiltration. CLINICAL RELEVANCE: Resin-based composite and compomer restorations show similar survival rates of more than 43% (annual failure rates less than 11.5%) after 5 years for restoration of primary molars.


Assuntos
Anestesia/métodos , Cárie Dentária , Criança , Compômeros , Resinas Compostas , Falha de Restauração Dentária , Restauração Dentária Permanente , Seguimentos , Cimentos de Ionômeros de Vidro , Humanos , Estudos Retrospectivos
3.
Mol Inform ; 38(11-12): e1800145, 2019 11.
Artigo em Inglês | MEDLINE | ID: mdl-31535472

RESUMO

Protein-protein interactions are an important phenomenon in biological processes and functions. We used the manually curated non-redundant dataset of 118 phycocyanin interfaces to gain additional insight into this phenomenon using a robust inter-atomic non-covalent interaction analyzing tool PPCheck. Our observations indicate that there is a relatively high composition of hydrophobic residues at the interfaces. Most of the interface residues are clustered at the middle of the range which we call "standard-size" interfaces. Furthermore, the multiple interaction patterns founded in the present study indicate that more than half of the residues involved in these interactions participate in multiple and water-bridged hydrogen bonds. Thus, hydrogen bonds contribute maximally towards the stability of protein-protein complexes. The analysis shows that hydrogen bond energies contribute to about 88 % to the total energy and it also increases with interface size. Van der Waals (vdW) energy contributes to 9.3 %±1.7 % on average in these complexes. Moreover, there is about 1.9 %±1.5 % contribution by electrostatic energy. Nevertheless, the role by vdW and electrostatic energy could not be ignored in interface binding. Results show that the total binding energy is more for large phycocyanin interfaces. The normalized energy per residue was less than -16 kJ mol-1 , while most of them have energy in the range from -6 to -14 kJ mol-1 . The non-covalent interacting residues in these proteins were found to be highly conserved. Obtained results might contribute to the understanding of structural stability of this class of evolutionary essential proteins with increased practical application and future designs of novel protein-bioactive compound interactions.

4.
Chem Biol Interact ; 311: 108787, 2019 Sep 25.
Artigo em Inglês | MEDLINE | ID: mdl-31400341

RESUMO

Antipsychotic drugs interfere with the antioxidant defense system provoking complex and often toxicological effects. Here we examined differences in plasma albumin reduced free thiol (SH) group content and its reactivity as a consequence of clozapine (CLZ) and ziprasidone (ZIP) binding. Chronic administration of CLZ reduced, whereas treatment with ZIP increased albumin-SH content in rats. Regardless of the ratio of stearic acid (SA) bound to protein, in vitro binding of ZIP to human serum albumin (HSA) increased both the SH group level and reactivity. In contrast, the effect of CLZ on HSA-SH reactivity was dependent on HSA to SA molar ratio. CLZ binding was accompanied by an increase in HSA-SH reactivity in samples with normal, but a reduction of its reactivity level with higher SA/HSA ratio, compared to drug-free samples. We demonstrate by steady-state fluorescence quenching studies that an increase in SA binding to HSA is associated with a significant reduction of binding constant for both antipsychotics. In addition, this is the first report of quantitative characterization of ZIP binding to HSA. Our findings suggest that albumin-SH content and reactivity is modulated by ZIP towards an increased antioxidant defense capacity in circulation, as opposed to CLZ, which can contribute to the safer, more effective treatment of schizophrenia.


Assuntos
Clozapina/química , Ácidos Graxos/química , Piperazinas/química , Albumina Sérica/química , Compostos de Sulfidrila/química , Tiazóis/química , Animais , Clozapina/metabolismo , Ácidos Graxos/metabolismo , Humanos , Masculino , Piperazinas/metabolismo , Ligação Proteica , Ratos , Ratos Wistar , Albumina Sérica/metabolismo , Espectrometria de Fluorescência , Espectrofotometria , Compostos de Sulfidrila/análise , Compostos de Sulfidrila/metabolismo , Tiazóis/metabolismo
5.
J Inorg Biochem ; 199: 110758, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31299379

RESUMO

Anticancer activity of Pd complexes 1-5 with bidentate N-heteroaromatic hydrazone ligands was investigated on human acute monocytic leukemia (THP-1; cells in a suspension) and human mammary adenocarcinoma (MCF-7; two-dimensional layer and three-dimensional spheroid tumor model) cell lines. For the Pd(II) complexes with condensation products of ethyl hydrazainoacetate and quinoline-8-carboxaldehyde (complex 1) and 2-formylpyridine (complex 3), for which apoptosis was determined as a mechanism of anticancer activity, further investigation revealed that they arrest the cell cycle in G0/G1 phase, induce generation of reactive oxygen species and inhibit Topoisomerase I in vitro. In silico studies corroborate experimental findings that these complexes show topoisomerase inhibition activity in the micromolar range and indicate binding to a DNA's minor groove as another potential target. Based on the results obtained by circular dichroism and fluorescence spectroscopy measurements, the most active complexes are suitable to be delivered to a blood stream via human serum albumin.

6.
Int J Biol Macromol ; 128: 74-79, 2019 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-30684573

RESUMO

Fibrinogen, a protein involved in blood coagulation, is very susceptible to oxidation. Oxidation alters its function and usually makes it more thrombogenic. Bilirubin, an end-product of the haem degradation in vertebrates, is known for its antioxidant properties. The present paper describes interaction between fibrinogen and bilirubin, and the influence of bilirubin on the formation of fibrin and protection against oxidation. The binding constant of 4.5 × 104 M-1 was determined for the fibrinogen/bilirubin complex at 37 °C. There is no change in secondary and tertiary structure of fibrinogen or its thermal stability upon bilirubin binding. The binding site of fibrinogen is not stereospecific for bilirubin and is able to accommodate both bilirubin conformers. A change in absorption maximum of bilirubin occurs upon its interaction with fibrinogen, suggesting an alteration in the conformation of bilirubin to the more cyclic one. Bilirubin exerts antioxidant effect on fibrinogen, preventing its carbonylation and aggregation. The presence of bilirubin induces the formation of fibrin with thicker fibres, as assessed by the coagulation assay. Fibrinogen and bilirubin interact at physiological concentrations, bilirubin may act as an antioxidant for fibrinogen and may modulate an important event in haemostasis, which altogether suggests possible physiological relevance of this interaction.


Assuntos
Bilirrubina/química , Bilirrubina/metabolismo , Fibrinogênio/química , Fibrinogênio/metabolismo , Coagulação Sanguínea , Testes de Coagulação Sanguínea , Dicroísmo Circular , Fluorometria , Humanos , Oxirredução , Ligação Proteica , Termodinâmica
7.
Food Chem ; 269: 43-52, 2018 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-30100456

RESUMO

In this study, we investigated structural aspects of covalent binding of food derived blue pigment phycocyanobilin (PCB) to bovine ß-lactoglobulin (BLG), major whey protein, by spectroscopic, electrophoretic, mass spectrometry and computational methods. At physiological pH (7.2), we found that covalent pigment binding via free cysteine residue is slow (ka = 0.065 min-1), of moderate affinity (Ka = 4 × 104 M-1), and stereo-selective. Binding also occurs at a broad pH range and under simulated gastrointestinal conditions. Adduct formation rises with pH, and in concentrated urea (ka = 0.101 min-1). The BLG-PCB adduct has slightly altered secondary and tertiary protein structure, and bound PCB has higher fluorescence and more stretched conformation than free chromophore. Combination of steered molecular dynamic for disulfide exchange, non-covalent and covalent docking, favours Cys119 residue in protein calyx as target for covalent BLG-PCB adduct formation. Our results suggest that this adduct can serve as delivery system of bioactive PCB.


Assuntos
Lactoglobulinas/química , Ficobilinas/química , Ficocianina/química , Animais , Sítios de Ligação , Bovinos , Concentração de Íons de Hidrogênio , Pigmentação
8.
Front Chem ; 6: 247, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30018949

RESUMO

The novel approach in the treatment of complex multifactorial diseases, such as neurodegenerative disorders and cancer, requires a development of efficient multi-targeting oriented drugs. Since oxidative stress significantly contributes to the pathogenesis of cancer and neurodegenerative disorders, potential drug candidates should possess good antioxidant properties. Due to promising biological activities shown for structurally related (1,3-thiazol-2-yl)hydrazones, a focused library of 12 structurally related benzylidene-based (1,3-selenazol-2-yl)hydrazones was designed as potential multi-targeting compounds. Monoamine oxidases (MAO) A/B inhibition properties of this class of compounds have been investigated. Surprisingly, the p-nitrophenyl-substituted (1,3-selenazol-2-yl)hydrazone 4 showed MAO B inhibition in a nanomolar concentration range (IC50 = 73 nM). Excellent antioxidant properties were confirmed in a number of different in vitro assays. Antiproliferative activity screening on a panel of six human solid tumor cell lines showed that potencies of some of the investigated compounds was comparable or even better than that of the positive control 5-fluorouracil. In-silico calculations of ADME properties pointed to promising good pharmacokinetic profiles of investigated compounds. Docking studies suggest that some compounds, compared to positive controls, have the ability to strongly interact with targets relevant to cancer such as 5'-nucleotidase, and to neurodegenerative diseases such as the small conductance calcium-activated potassium channel protein 1, in addition to confirmation of inhibitory binding at MAO B.

9.
J Toxicol Environ Health A ; 81(17): 844-853, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30036154

RESUMO

Atypical antipsychotics produce severe side effects including myocarditis that may be attributed to oxidative stress. The aim of this study was to investigate the influence of clozapine, ziprasidone, and sertindole on rat heart morphology and determine whether redox imbalane plays a role in development of histopathological changes. Adult 3-month-old male Wistar rats were treated with recommended daily dose for selected drugs. After 4 week treatment histopathological analysis of the heart was performed and expression and activity of antioxidant enzymes determined. All examined drugs induced histopathological changes that were characterized as toxic myocarditis. Degenerative changes in cardiomyocytes were accompanied by lymphocytic infiltration as well as pericardial histopathological alterations in all treated groups. The least prominent changes were observed in sertindole-treated animals, and most severe with clozapine. Clozapine increased superoxide dismutase 1 (SOD1) activity while ziprasidone reduced glutathione reductase (GR) activity. Sertindole exerted no marked effect on antioxidant enzyme function in the heart even though myocardial degeneration was noted. In conclusion, treatment with clozapine or ziprasidone induced pathophysiological alterations in rat heart, which appeared to be associated disturbances in antioxidant capacity. Abbreviation: AAP, Atypical antipsychotics; ROS, reactive oxygen species; SOD1, Copper-zinc superoxide dismutase; SOD2, Manganese superoxide dismutase; CAT, Catalase; GPx, Glutathione peroxidase; GR, Glutathione reductase; H&E, hematoxylin and eosin stain; TNF- α, tumor necrosis factor alpha.


Assuntos
Antioxidantes/metabolismo , Antipsicóticos/toxicidade , Clozapina/toxicidade , Coração/efeitos dos fármacos , Imidazóis/toxicidade , Indóis/toxicidade , Piperazinas/toxicidade , Tiazóis/toxicidade , Animais , Masculino , Miocárdio/enzimologia , Miocárdio/patologia , Oxirredução , Ratos , Ratos Wistar
10.
Food Chem ; 239: 1090-1099, 2018 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-28873526

RESUMO

Phycocyanobilin (PCB) is a blue tetrapyrrole chromophore of C-phycocyanin, the main protein of the microalga Spirulina, with numerous proven health-related benefits. We examined binding of PCB to bovine serum albumin (BSA) and how it affects protein and ligand stability. Protein fluorescence quenching and microscale thermophoresis demonstrated high-affinity binding (Ka=2×106M-1). Spectroscopic titration with molecular docking analysis revealed two binding sites on BSA, at the inter-domain cleft and at subdomain IB, while CD spectroscopy indicated stereo-selective binding of the P conformer of the pigment to the protein. The PCB protein complex showed increased thermal stability. Although complex formation partly masked the antioxidant properties of PCB and BSA, a mutually protective effect against free radical-induced oxidation was found. BSA could be suitable for delivery of PCB as a food colorant or bioactive component. Our results also highlight subtle differences between PCB binding to bovine vs. human serum albumin.


Assuntos
Ficobilinas/química , Ficocianina/química , Soroalbumina Bovina/química , Animais , Sítios de Ligação , Bovinos , Humanos , Simulação de Acoplamento Molecular , Ligação Proteica , Espectrometria de Fluorescência
11.
EuroIntervention ; 13(Z): Z59-Z63, 2017 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-28504233

RESUMO

Serbia's interventional community has been facing the multifaceted challenge of an ageing population with cardiovascular diseases as the primary cause of death nationwide, coronary artery disease (CAD) being the most prevalent subset. The following two fields of activity have marked the trajectory of progress in the field of interventional cardiology in Serbia: first, the expansion of the infrastructure, mainly through the opening of new catheterisation laboratories across all of the country's administrative regions, which has resulted in better accessibility to coronary interventions for the general population; second, the creation of national platforms for continuous education, training and the promotion of clinical research in interventional cardiology, with close programmatic links to European Association of Percutaneous Cardiovascular Interventions (EAPCI)-based educational initiatives, including the curriculum for interventional cardiology. As growth seems to be inherent to the concept of progress, we report here on the expanding numbers of coronary interventions in the period between January 2010 and December 2015, and the early experiences with structural heart interventions in Serbia.


Assuntos
Cateterismo Cardíaco , Procedimentos Cirúrgicos Cardíacos , Doença da Artéria Coronariana/cirurgia , Coração , Cateterismo Cardíaco/métodos , Procedimentos Cirúrgicos Cardíacos/métodos , Currículo/estatística & dados numéricos , Humanos , Pesquisa , Sérvia , Sociedades Médicas/estatística & dados numéricos
12.
PLoS One ; 11(12): e0167973, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27959940

RESUMO

Phycocyanobilin (PCB) binds with high affinity (2.2 x 106 M-1 at 25°C) to human serum albumin (HSA) at sites located in IB and IIA subdomains. The aim of this study was to examine effects of PCB binding on protein conformation and stability. Using 300 ns molecular dynamics (MD) simulations, UV-VIS spectrophotometry, CD, FT-IR, spectrofluorimetry, thermal denaturation and susceptibility to trypsin digestion, we studied the effects of PCB binding on the stability and rigidity of HSA, as well as the conformational changes in PCB itself upon binding to the protein. MD simulation results demonstrated that HSA with PCB bound at any of the two sites showed greater rigidity and lower overall and individual domain flexibility compared to free HSA. Experimental data demonstrated an increase in the α-helical content of the protein and thermal and proteolytic stability upon ligand binding. PCB bound to HSA undergoes a conformational change to a more elongated conformation in the binding pockets of HSA. PCB binding to HSA stabilizes the structure of this flexible transport protein, making it more thermostable and resistant to proteolysis. The results from this work explain at molecular level, conformational changes and stabilization of HSA structure upon ligand binding. The resultant increased thermal and proteolytic stability of HSA may provide greater longevity to HSA in plasma.


Assuntos
Simulação de Acoplamento Molecular , Ficobilinas/farmacologia , Ficocianina/farmacologia , Albumina Sérica/química , Sítios de Ligação , Ficobilinas/química , Ficocianina/química , Ligação Proteica , Estabilidade Proteica , Albumina Sérica/metabolismo , Spirulina/química
13.
J Toxicol Environ Health A ; 79(20): 905-11, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27644343

RESUMO

The use of atypical antipsychotic drugs (APD) was reported to be associated with adverse effects on the kidneys. Thus, the aim of this study was to examine whether APD exerted their adverse effects by interfering with the renal antioxidant defense system. Male 3-mo-old Wistar rats were treated for 28 d with ziprasidone (ZIP), clozapine (CLO), or sertindole (SER) using a daily dose recommended for antipsychotic drug therapy. The expression and activities of antioxidant enzymes superoxide dismutase (SOD) type 1 and type 2, catalase (CAT), glutathione reductase (GR), and glutathione S-transferases (GSTs) activity were measured in the kidneys. Changes in the kidneys were also evaluated histologically. Ziprasidone, CLO, and SER reduced renal SOD type 1 and type 2 activities. Decreased CAT activity was observed only in SER-treated rats. An inhibition in GR activity and increased activity of GST was found only after treatment with CLO. Histological analysis showed dilatation of proximal tubules in kidneys with all three drugs. In conclusion, data indicate that redox disturbances may contribute to renal morphologic alterations in proximal tubules in rats treated with all APD.


Assuntos
Antioxidantes/metabolismo , Antipsicóticos/toxicidade , Clozapina/toxicidade , Imidazóis/toxicidade , Indóis/toxicidade , Estresse Oxidativo/efeitos dos fármacos , Piperazinas/toxicidade , Tiazóis/toxicidade , Animais , Rim/efeitos dos fármacos , Masculino , Distribuição Aleatória , Ratos , Ratos Wistar
14.
Int Urol Nephrol ; 48(10): 1683-90, 2016 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-27412679

RESUMO

PURPOSE: Unfavorable lipid profile is a major risk factor for cardiovascular disease in renal pathology. In this study, we compared chronic renal patients and healthy controls with different LDL phenotypes (A or B) in respect of various biochemical parameters related to cardiovascular disease. METHODS: Oxidative stress and anti-oxidative defense parameters [thiobarbituric acid-reacting substances (TBARS), total oxidative status (TOS), total anti-oxidative status (TAS), total protein sulfhydryl (-SH) groups], as well as red blood cell cholesterol distribution were assessed in 40 renal patients and 40 control subjects by standardized assays. LDL particle diameters were determined by polyacrylamide gradient gel electrophoresis. LDL particles are subdivided according to their size into large LDL A phenotype (diameter >25.5 nm) and small LDL B phenotype (diameter ≤25.5 nm). RESULTS: Renal patients with LDL A phenotype had increased oxidative stress (TOS: p < 0.01, and TBARS: p < 0.001) and decreased total SH- groups (p < 0.001) compared to controls with the same LDL phenotype. A notable decrease in hemoglobin-cholesterol adduct was detected in patients with LDL A phenotype (p < 0.001) and LDL B phenotype (p < 0.05) compared with appropriate controls. LDL B phenotype was characterized with increased TBARS (p < 0.05) compared with LDL A phenotype in control group. CONCLUSION: Increased oxidative stress, decreased anti-oxidative defense followed with unfavorable changes in hemoglobin-cholesterol binding capacity, could have important influence on cardiovascular disease risk in renal patients regardless of LDL phenotype.


Assuntos
Doenças Cardiovasculares/epidemiologia , LDL-Colesterol , Hemoglobinas , Insuficiência Renal Crônica , Proteínas Adaptadoras de Transporte Vesicular/genética , Adulto , Idoso , LDL-Colesterol/genética , LDL-Colesterol/metabolismo , Membrana Eritrocítica/metabolismo , Feminino , Hemoglobinas/análise , Hemoglobinas/metabolismo , Humanos , Masculino , Pessoa de Meia-Idade , Estresse Oxidativo , Fenótipo , Insuficiência Renal Crônica/epidemiologia , Insuficiência Renal Crônica/metabolismo , Fatores de Risco , Estatística como Assunto , Substâncias Reativas com Ácido Tiobarbitúrico/metabolismo
15.
J Proteomics ; 147: 132-139, 2016 09 16.
Artigo em Inglês | MEDLINE | ID: mdl-27084687

RESUMO

C-phycocyanin, the major protein of cyanobacteria Spirulina, possesses significant antioxidant, anti-cancer, anti-inflammatory and immunomodulatory effects, ascribed to covalently attached linear tetrapyrrole chromophore phycocyanobilin. There are no literature data about structure and biological activities of released peptides with bound chromophore in C-phycocyanin digest. This study aims to identify chromopeptides obtained after pepsin digestion of C-phycocyanin and to examine their bioactivities. C-phycocyanin is rapidly digested by pepsin in simulated gastric fluid. The structure of released chromopeptides was analyzed by high resolution tandem mass spectrometry and peptides varying in size from 2 to 13 amino acid residues were identified in both subunits of C-phycocyanin. Following separation by HPLC, chromopeptides were analyzed for potential bioactivities. It was shown that all five chromopeptide fractions have significant antioxidant and metal-chelating activities and show cytotoxic effect on human cervical adenocarcinoma and epithelial colonic cancer cell lines. In addition, chromopeptides protect human erythrocytes from free radical-induced hemolysis in antioxidative capacity-dependant manner. There was a positive correlation between antioxidative potency and other biological activities of chromopeptides. Digestion by pepsin releases biologically active chromopeptides from C-phycocyanin whose activity is mostly related to the antioxidative potency provided by chromophore.


Assuntos
Pepsina A/metabolismo , Peptídeos/farmacologia , Ficocianina/metabolismo , Spirulina/química , Antioxidantes , Linhagem Celular Tumoral , Células Cultivadas , Neoplasias do Colo/tratamento farmacológico , Cor , Eritrócitos/efeitos dos fármacos , Feminino , Hemólise/efeitos dos fármacos , Humanos , Peptídeos/metabolismo , Peptídeos/uso terapêutico , Neoplasias do Colo do Útero/tratamento farmacológico
16.
Appl Opt ; 54(9): 2193-8, 2015 Mar 20.
Artigo em Inglês | MEDLINE | ID: mdl-25968500

RESUMO

For the first time to our knowledge, we apply the multiple signal classification (MUSIC) algorithm to signals obtained from a self-mixing flow sensor. We find that MUSIC accurately extracts the fluid velocity and exhibits a markedly better signal-to-noise ratio (SNR) than the commonly used fast Fourier transform (FFT) method. We compare the performance of the MUSIC and FFT methods for three decades of scatterer concentration and fluid velocities from 0.5 to 50 mm/s. MUSIC provided better linearity than the FFT and was able to accurately function over a wider range of algorithm parameters. MUSIC exhibited excellent linearity and SNR even at low scatterer concentration, at which the FFT's SNR decreased to impractical levels. This makes MUSIC a particularly attractive method for flow measurement systems with a low density of scatterers such as microfluidic and nanofluidic systems and blood flow in capillaries.

17.
Appl Opt ; 54(1): 18-26, 2015 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-25967002

RESUMO

We present a comprehensive analysis of factors influencing the morphology of the Doppler spectrum obtained from a laser-feedback interferometer. We explore the effect of optical system parameters on three spectral characteristics: central Doppler frequency, broadening, and signal-to-noise ratio. We perform four sets of experiments and replicate the results using a Monte Carlo simulation calibrated to the backscattering profile of the target. We classify the optical system parameters as having a strong or weak influence on the Doppler spectrum. The calibrated Monte Carlo approach accurately reproduces experimental results, and allows one to investigate the detailed contribution of system parameters to the Doppler spectrum, which are difficult to isolate in experiment.

18.
J Biol Inorg Chem ; 20(3): 475-85, 2015 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-25502146

RESUMO

We have analyzed the influence of anion-π interactions to the stability of Sm/LSm assemblies. The side chain of Glu is more likely to be in anion-π interactions than Asp. Phe has the highest occurrence in these interactions than the other two π residues. Among the anion-π residue pairs, Glu-Phe residue pair showed the maximum number of anion-π. We have found hot-spot residues forming anion-π interactions, and Glu-Phe is the most common hot-spot interacting pair. The significant numbers of anion-π interacting residues identified in the dataset were involved in the formation of multiple anion-π interactions. More than half of the residues involved in these interactions are evolutionarily conserved. The anion-π interaction energies are distance and orientation dependent. It was found that anion-π interactions showed energy less than -15 kcal mol(-1), and most of them have energy in the range -2 to -9 kcal mol(-1). Solvent accessibility pattern of Sm/LSm proteins reveals that all of the interacting residues are preferred to be in buried regions. Most of the interacting residues preferred to be in strand. A significant percentage of anion-π interacting residues are located as stabilization centers and thus might provide additional stability to these proteins. The simultaneous interaction of anions and cations on different faces of the same π-system has been observed. On the whole, the results presented in this work will be very useful for understanding the contribution of anion-π interaction to the stability of Sm/LSm proteins.


Assuntos
Proteínas de Ligação a RNA/química , Ribonucleoproteínas Nucleares Pequenas/química , Simulação por Computador , Estabilidade Proteica , Estrutura Secundária de Proteína , Relação Estrutura-Atividade
19.
Protoplasma ; 252(4): 947-58, 2015 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-25408427

RESUMO

In this work, we have analyzed the influence of cation-π interactions to the stability of Sm/LSm assemblies and their environmental preferences. The number of interactions formed by arginine is higher than lysine in the cationic group, while histidine is comparatively higher than phenylalanine and tyrosine in the π group. Arg-Tyr interactions are predominant among the various pairs analyzed. The furcation level of multiple cation-π interactions is much higher than that of single cation-π interactions in Sm/LSm interfaces. We have found hot spot residues forming cation-π interactions, and hot spot composition is similar for all aromatic residues. The Arg-Phe pair has the strongest interaction energy of -8.81 kcal mol(-1) among all the possible pairs of amino acids. The extent of burial of the residue side-chain correlates with the ΔΔG of binding for residues in the core and also for hot spot residues cation-π bonded across the interface. Secondary structure of the cation-π residues shows that Arg and Lys preferred to be in strand. Among the π residues, His prefers to be in helix, Phe prefers to be in turn, and Tyr prefers to be in strand. Stabilization centers for these proteins showed that all the five residues found in cation-π interactions are important in locating one or more of such centers. More than 50 % of the cation-π interacting residues are highly conserved. It is likely that the cation-π interactions contribute significantly to the overall stability of Sm/LSm proteins.


Assuntos
Aminoácidos/química , Cátions/química , Estrutura Secundária de Proteína , Termodinâmica
20.
Appl Opt ; 53(17): 3723-36, 2014 Jun 10.
Artigo em Inglês | MEDLINE | ID: mdl-24921138

RESUMO

Self-mixing laser sensors show promise for a wide range of sensing applications, including displacement, velocimetry, and fluid flow measurements. Several techniques have been developed to simulate self-mixing signals; however, a complete and succinct process for synthesizing self-mixing signals has so far been absent in the open literature. This article provides a systematic numerical approach for the analysis of self-mixing sensors using the steady-state solution to the Lang and Kobayashi model. Examples are given to show how this method can be used to synthesize self-mixing signals for arbitrary feedback levels and for displacement, distance, and velocity measurement. We examine these applications with a deterministic stimulus and discuss the velocity measurement of a rough surface, which necessitates the inclusion of a random stimulus.

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