Amando Ito - Academia.edu (original) (raw)
Papers by Amando Ito
Bulletin of the American Physical Society, 2019
Journal of Molecular Liquids, 2021
Abstract Brazilian green propolis is a well-known therapeutic product, commonly used in folk medi... more Abstract Brazilian green propolis is a well-known therapeutic product, commonly used in folk medicine. Artepillin C is the major compound of Brazilian green propolis and has received considerable attention owing to its lipophilic affinity and antioxidant activity, enabling the use against lipid oxidation caused by free radicals, which is a first step before degenerative diseases. The protective effect of Artepillin C against lipid oxidation was evaluated here on models of lipid membranes based on Langmuir monolayers and giant unilamellar vesicles (GUVs) formed of 1,2-dioleoyl-sn-glycero-3-phosphocholine DOPC under oxidative stress induced by the photoactivated erythrosin. Our findings show that the lipophilic character of Artepillin C allows the donation of a hydrogen atom of the phenolic hydroxyl group to the lipid radical of both mono and bilayer, avoiding the formation of truncated aldehyde lipids, interrupting oxidative reactions mediated by reactive oxygen species (ROS), therefore playing a role as an antioxidant compound in the lipid environment. The affinity of Artepillin C for lipid structures, together with its antioxidant potential, preclude the lipid peroxidation caused by reactive species.
Current Nanoscience, 2018
In the last 40 years, scientific efforts were focused on the efficiency improvement in organic ph... more In the last 40 years, scientific efforts were focused on the efficiency improvement in organic photovoltaic devices. Bleaching agents were used to absorb UV light and convert it into lower energy radiation appear as potential candidates for further improvements. The present contribution investigated the effect of adding umbelliferone to poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) on its optical and electrical properties. Characterizations were performed under various umbelliferone concentrations. Fluorescence decay lifetimes were obtained using a MicroTime 200 system (PicoQuant). The UV–vis absorption spectra were obtained with a GE Healthcare Ultrospec 2100 pro Spectrometer. The electrical conductivity measurements as a function of temperature using a cryostat model ARS CS202AE-DMX-1AL. The absorbance increases around 325 nm and decreases in the near infrared s the umbelliferone concentration is increased. It also decreases the absorption in the visible spectrum, concomitantly with a significant increase in the UV region. The electrical conductivity for the umbelliferone doped PEDOT:PSS films display an increase with increasing temperature, but does not follow a linear behavior with the increase of umbelliferone concentration in the films. It was shown that the absorbance displays a redshift in doped samples, while photoluminescence experiments demonstrated that UV light is converted to the visible spectrum more efficiently, which is a desirable feature for photovoltaic devices. Also, the electrical conductivity of PEDOT:PSS is increased for moderate umbelliferone concentrations.
Photochemistry and Photobiology, 2019
Brazilian green propolis is one of the bee products most consumed in the world to prevent disease... more Brazilian green propolis is one of the bee products most consumed in the world to prevent diseases, owing antioxidant, antimicrobial, anti-inflammatory and antitumor activities. The major component of Brazilian green propolis is Artepillin C (ArtC), a cinnamic acid derivative with two prenylated groups that improve the affinity of the compound for lipophilic environment. Here we have employed optical absorption and fluorescence techniques to draw conclusions on how ArtC interacts with amphiphilic aggregates commonly used as model membranes having different charges in the polar head group. Optical absorption spectra were representative of the protonation state of ArtC, dictated by the local pH at the surface of micelles and lipid vesicles. Fluorescence results Accepted Article This article is protected by copyright. All rights reserved. showed that, in the presence of micelles and vesicles, the polarizability around ArtC was modified, compared to the value in aqueous medium, and the molecule should be located preferentially on the surface region of the model membranes, with an enhanced interaction with the less ordered state of the lipid vesicles.
Food Science & Nutrition, 2019
Free radicals are atoms or molecules with unpaired electrons that are highly unstable and active ... more Free radicals are atoms or molecules with unpaired electrons that are highly unstable and active toward chemical reactions with other molecules. They are constantly created from cell metabolism and can lead to damage to proteins, lipids, RNA, and DNA, among other molecules (Chan, Gan, & Corke, 2016). An excess of free radicals is related to various severe diseases, including cancer, atherosclerosis, stroke, Alzheimer's, and Parkinson's, among others (Aruoma, 1998; Carocho & Ferreira, 2013). Antioxidants are substances able to prevent or inhibit oxidation processes in human body as well as in food product (Duda-Chodak & Tarko, 2007). Free radicals can be inhibited by antioxidants.
International Journal of Pharmaceutics, 2017
The sesquiterpene nerolidol and the monoterpene limonene are potent skin-permeation enhancers tha... more The sesquiterpene nerolidol and the monoterpene limonene are potent skin-permeation enhancers that have also been shown to have antitumor, antibacterial, antifungal and antiparasitic activities. Because terpenes are membrane-active compounds, we used electron paramagnetic resonance (EPR) spectroscopy of three membrane spin labels combined with the fluorescence spectroscopy of three lipid probes to study the interactions of these terpenes with stratum corneum (SC) intercellular membranes. An experimental apparatus was developed to assess the lipid fluidity of hydrated SC membranes via the fluorescence anisotropy of extrinsic membrane probes. Both EPR and fluorescence probes indicated that the intercellular membranes of neonatal SC rats undergo a main phase transition at approximately 50°C. Taken together, the results indicated that treatment with 1% nerolidol (v/v) caused large fluidity increases in the more ordered phases of SC membranes and that these effects gradually decreased with increasing temperature. Additionally, compared with (+)-limonene, nerolidol was better able to change the SC membrane dynamics. EPR and fluorescence data suggest that these terpenes act as spacers in lipid packaging and create increased lipid disorder in the more ordered regions and phases of SC membranes, notably leading to a population of probes with less restricted motion.
International journal of biological macromolecules, 2017
Glossoscolex paulistus extracellular hemoglobin (HbGp) stability has been followed, in the presen... more Glossoscolex paulistus extracellular hemoglobin (HbGp) stability has been followed, in the presence of urea, using fluorescein isothiocyanate (FITC). Binding of FITC to HbGp results in a significant quenching of probe fluorescence. Tryptophan emission decays present four characteristic lifetimes: two in the sub-nanosecond/picosecond, and two in the nanosecond time ranges. Tryptophan decays for pure HbGp and HbGp-FITC systems are similar. In the absence of denaturant, and up to 2.5mol/L of urea, the shorter lifetimes predominate. At 3.5 and 6.0mol/L of urea, the longer lifetimes increase significantly their contribution. Urea-induced unfolding process is characterized by protein oligomeric dissociation and denaturation of dissociated subunits. FITC emission decays for FITC-HbGp system are also multi-exponential with three lifetimes: two in the sub-nanosecond and one in the nanosecond range with a value similar to free probe in buffer. Increase of urea concentration leads to increase ...
Journal of Apicultural Research, 2017
Propolis is a bee product that results from the mixture of beeswax and resinous compounds. It can... more Propolis is a bee product that results from the mixture of beeswax and resinous compounds. It can scavenge free radicals; therefore, it displays antioxidant activity. Here, we have investigated the antioxidant potential of propolis produced by three Brazilian stingless bee species: Melipona quadrifasciata anthidiodes (Mandaçaia) and Tetragona clavipes (Borá), which inhabit the southeastern region of Brazil (state of São Paulo), and Scaptotrigona spp. (Tubi), which inhabits the northeastern region of Brazil (state of Maranhão). The antioxidant activities of propolis produced by different bee species were compared to the well-known antioxidant activity of green propolis, produced by the honey bee Apis mellifera. The ethanolic extract of propolis produced by Mandaçaia displayed the strongest antioxidant activity. The activity was even stronger than the antioxidant activity of green propolis. The ethyl acetate and aqueous fraction of propolis produced by Mandaçaia presented the highest antioxidant activity. This result agreed with the higher total polyphenol content verified in this propolis. high performance liquid chromatography analysis revealed that the groups of compounds present in propolis produced by Mandaçaia, Tubi, and Borá were not the same as those previously identified as the main constituents of green propolis. In fact, propolis produced by Mandaçaia contained many other polyphenols in the fingerprint, and hence its composition requires further elucidation. Actividad antioxidante de tres tipos de propó leos de abeja sin aguijó n y propó leos verdes El propó leos es un producto de abeja que resulta de la mezcla de cera de abejas y compuestos resinosos. Puede eliminar radicales libres; por lo tanto, muestra actividad antioxidante. En este trabajo se investigó el potencial antioxidante del propó leo producido por tres especies de abejas sin aguijó n: Melipona quadrifasciata anthidiodes (Mandaçaia) y Tetragona clavipes (Borá), que habitan la regió n sureste de Brasil (estado de São Paulo) y Scaptotrigona spp. (Tubi), que habita la regió n noreste de Brasil (estado de Maranhão). Las actividades antioxidantes del propó leos producido por diferentes especies de abejas fueron comparadas con la conocida actividad antioxidante del propó leos verde, producido por la abeja Apis mellifera. El extracto etanó lico de propó leos (EEP) producido por Mandaçaia mostró la mayor actividad antioxidante. La actividad fue aún más fuerte que la actividad antioxidante del propó leos verde. El acetato de etilo y la fracció n acuosa de propó leos producidos por Mandaçaia presentaron la mayor actividad antioxidante. Este resultado coincidió con el mayor contenido de polifenoles totales verificado en este propó leos. El análisis por HPLC reveló que los grupos de compuestos presentes en los propó leos producidos por Mandaçaia, Tubi y Borá no eran los mismos que los previamente identificados como los principales constituyentes del propó leos verde. De hecho, el propó leos producido por Mandaçaia contenía muchos otros polifenoles en la huella, y por lo tanto su composició n requiere una dilucidació n adicional.
Biochimica et biophysica acta, Apr 24, 2017
The study of Acridine Orange (AO) spectral characteristics and the quenching of its singlet and t... more The study of Acridine Orange (AO) spectral characteristics and the quenching of its singlet and triplet excited states by TEMPO radical at its binding to DNA in the function of the DNA concentration and in the absence and presence of NaCl is reported. The study was performed using steady-state and time resolved optical absorption and florescence, fluorescence correlation spectroscopy and resonant light scattering techniques. The presence of different species in equilibrium: AO monomers and aggregates bound to DNA, has been demonstrated, their relative content depending on the DNA and the AO concentrations. At high DNA concentration the AO monomers are protected against the contact with other molecules, thus reducing the AO excited state quenching. The addition of NaCl reduces the AO binding constant to DNA, thus reducing the AO and DNA aggregation. The interaction of AO with DNA is a complex process, including aggregation and disaggregation of both components. This modifies the AO e...
Journal of medicinal chemistry, Oct 26, 2016
The complexes cis-[Ru(phen)2(Apy)2](2+), Apy = 4-aminopyridine and 3,4-aminopyridine are stable i... more The complexes cis-[Ru(phen)2(Apy)2](2+), Apy = 4-aminopyridine and 3,4-aminopyridine are stable in aqueous solution with strong visible absorption. They present emission in the visible region with long lifetime that accumulates in the cytoplasm of Neuro2A cell line without appreciable cytotoxicity. The complexes also serve as mixed-type reversible inhibitors of human AChE and BuChE with high active site contact. cis-[Ru(phen)2(3,4Apy)2](2+) competes efficiently with DMPO by the OH(•) radical. Luminescence, using fluorescence lifetime imaging (FLIM), enables real-time imaging of the conformational changes of the self-aggregation of Aβ with incubation of complexes (0-24 hours) in phosphate buffer at micromolar concentrations. By this technique, we identified protofibrills in the self-assembly of Aβ1-40 and globularstructures in the short fragment Aβ15-21 in aqueous solution.
Applied spectroscopy, Jan 5, 2016
The parathyroid glands are small and often similar to lymph nodes, fat, and thyroid tissue. These... more The parathyroid glands are small and often similar to lymph nodes, fat, and thyroid tissue. These glands are difficult to identify during surgery and a biopsy of the parathyroid for identification can lead to damage of the gland. The use of static and time-resolved fluorescence techniques to detect biochemical composition and tissue structure alterations could help to develop a portable, minimally invasive, and nondestructive method to assist medical evaluation of parathyroid tissues. In this study, we investigated 10 human parathyroid samples by absorbance, fluorescence, excitation, and time-resolved fluorescence measurements. Moreover, we compared the results of time-resolved fluorescence measurements with 59 samples of thyroid tissues. The fluorescence lifetimes with emission at 340 nm were 1.09 ± 0.10 and 4.46 ± 0.06 ns for healthy tissue, 1.01 ± 0.25 and 4.39 ± 0.36 ns for benign lesions, and 0.67 ± 0.36 and 3.92 ± 0.72 ns for malignant lesions. The lifetimes for benign and mal...
Semina: Ciências Sociais e Humanas, 1982
Hyperfine Interactions, 1986
Journal of Biomedical Optics, 2015
Fine-needle aspiration cytology is the standard technique to diagnose thyroid pathologies. Howeve... more Fine-needle aspiration cytology is the standard technique to diagnose thyroid pathologies. However, this method results in a high percentage of inconclusive and false negatives. The use of time-resolved fluorescence techniques to detect biochemical composition and tissue structure alterations could help to develop a portable, minimally invasive, and nondestructive method to assist during surgical procedures. This study aimed to use fluorescence lifetimes to differentiate healthy and benign tissues from malignant thyroid tissue. The thyroid tissue was excited at 298-300 nm and the fluorescence decay registered at 340 and 450 nm. We observed fluorescence lifetimes at 340 nm emission of 0.80 AE 0.26 and 3.94 AE 0.47 ns for healthy tissue; 0.90 AE 0.24 and 4.05 AE 0.46 ns for benign lesions; and 1.21 AE 0.14 and 4.63 AE 0.25 ns for malignant lesions. For 450 nm emissions, we obtain lifetimes of 0.25 AE 0.18 and 3.99 AE 0.39 ns for healthy tissue, 0.24 AE 0.17 and 4.20 AE 0.48 ns for benign lesions, 0.33 AE 0.32 and 4.55 AE 0.55 ns for malignant lesions. Employing analysis of variance, we differentiate malignant lesions from benign and healthy tissues. In addition, we use quadratic discriminant analysis to distinguish malignant from benign and healthy tissues with an accuracy of 76.1%, sensitivity of 74.7%, and specificity of 83.3%. These results indicate that time-resolved fluorescence can assist medical evaluation of thyroid pathologies during surgeries.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2015
h i g h l i g h t s Simulation of the theoretical electronic absorption spectra of orthoaminobenz... more h i g h l i g h t s Simulation of the theoretical electronic absorption spectra of orthoaminobenzoic acid by TD-DFT. Use of microhydration and PCM models to obtain spectra in aqueous medium. Analysis of geometric properties as well as intermolecular and intramolecular hydrogen bonds. When more water molecules surround ortho-aminobenzoic acid, the spectrum resembles the experimental data more closely. Microhydration and PCM models are necessary to fit the spectrum correctly.
Biospectroscopy, 1998
ortho-Aminobenzoic acid (Abz) has been used as a convenient fluorescent donor group in internally... more ortho-Aminobenzoic acid (Abz) has been used as a convenient fluorescent donor group in internally quenched fluorescent peptides, which are employed as substrates for several proteolytic enzymes. As Abz is usually bound to the N-amino terminal of these peptides, it is of interest to investigate the Abz group fluorescent properties bound to different amino acids. We report in this article the optical absorption and fluorescent properties, in aqueous media, of Abz bound to the ␣-amino group of Ala, Gly, Leu, Ile, Val, Pro, Phe, Arg, Glu, Met, Asn, Tyr, and Trp, with monomethylamidated ␣-carboxyl group. In order to explore the origin of the drastic reduction of Abz attached to N ␣ amino group of prolyl-peptides, we also examined the fluorescence properties of Abz-NHCH 3 , Abz-N(CH 3) 2 , and Abz-pyrrolidine. Molecular dynamics simulation and NMR data indicated a lack of periplanarity of the Abz-dimethylamide, which could be the origin of low fluorescence quantum yield of Abz-prolyl-peptides.
Latin America Optics and Photonics Conference, 2010
Page 1. Excited State Studies in Ruthenium Porphyrins Using Z-Scan Technique RN Sampaio, NM Barbo... more Page 1. Excited State Studies in Ruthenium Porphyrins Using Z-Scan Technique RN Sampaio, NM Barbosa Neto Institute of Physics Federal University of Uberlândia João Naves de Ávila Avenue, 2121 - Santa Mônica - Uberlândia ...
Letters in Peptide Science, 1995
A general procedure, using the commonly employed solid-phase peptide synthesis methodology for ob... more A general procedure, using the commonly employed solid-phase peptide synthesis methodology for obtaining internally quenched fluorogenic peptides with ortho-aminobenzoyl/dinitrophenyl groups as donor-acceptor pairs, is presented. The essential feature of this procedure is the synthesis of an N~-Boc or-Fmoc derivative of glutamic acid with the a-carboxyl group bound to N-(2,4-dinitrophenyl)-ethylenediamine (EDDnp), which provides the quencher moiety attached to the C-terminus of the substrate. The fluorescent donor group, ortho-aminobenzoic acid (Abz), is incorporated into the resin-bound peptide in the last coupling cycle. Depending on the resin type used, Abz-peptidyl-Gln-EDDnp or Abz-peptidyl-Glu-EDDnp is obtained. Using the procedure described above, substrates for human renin and tissue kallikreins were synthesised. Spectrofluorimetric measurements of Abz bound to the a-amino group of proline showed that strong quenching of Abz fluorescence occurs in the absence of any acceptor group.
Bulletin of the American Physical Society, 2019
Journal of Molecular Liquids, 2021
Abstract Brazilian green propolis is a well-known therapeutic product, commonly used in folk medi... more Abstract Brazilian green propolis is a well-known therapeutic product, commonly used in folk medicine. Artepillin C is the major compound of Brazilian green propolis and has received considerable attention owing to its lipophilic affinity and antioxidant activity, enabling the use against lipid oxidation caused by free radicals, which is a first step before degenerative diseases. The protective effect of Artepillin C against lipid oxidation was evaluated here on models of lipid membranes based on Langmuir monolayers and giant unilamellar vesicles (GUVs) formed of 1,2-dioleoyl-sn-glycero-3-phosphocholine DOPC under oxidative stress induced by the photoactivated erythrosin. Our findings show that the lipophilic character of Artepillin C allows the donation of a hydrogen atom of the phenolic hydroxyl group to the lipid radical of both mono and bilayer, avoiding the formation of truncated aldehyde lipids, interrupting oxidative reactions mediated by reactive oxygen species (ROS), therefore playing a role as an antioxidant compound in the lipid environment. The affinity of Artepillin C for lipid structures, together with its antioxidant potential, preclude the lipid peroxidation caused by reactive species.
Current Nanoscience, 2018
In the last 40 years, scientific efforts were focused on the efficiency improvement in organic ph... more In the last 40 years, scientific efforts were focused on the efficiency improvement in organic photovoltaic devices. Bleaching agents were used to absorb UV light and convert it into lower energy radiation appear as potential candidates for further improvements. The present contribution investigated the effect of adding umbelliferone to poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) on its optical and electrical properties. Characterizations were performed under various umbelliferone concentrations. Fluorescence decay lifetimes were obtained using a MicroTime 200 system (PicoQuant). The UV–vis absorption spectra were obtained with a GE Healthcare Ultrospec 2100 pro Spectrometer. The electrical conductivity measurements as a function of temperature using a cryostat model ARS CS202AE-DMX-1AL. The absorbance increases around 325 nm and decreases in the near infrared s the umbelliferone concentration is increased. It also decreases the absorption in the visible spectrum, concomitantly with a significant increase in the UV region. The electrical conductivity for the umbelliferone doped PEDOT:PSS films display an increase with increasing temperature, but does not follow a linear behavior with the increase of umbelliferone concentration in the films. It was shown that the absorbance displays a redshift in doped samples, while photoluminescence experiments demonstrated that UV light is converted to the visible spectrum more efficiently, which is a desirable feature for photovoltaic devices. Also, the electrical conductivity of PEDOT:PSS is increased for moderate umbelliferone concentrations.
Photochemistry and Photobiology, 2019
Brazilian green propolis is one of the bee products most consumed in the world to prevent disease... more Brazilian green propolis is one of the bee products most consumed in the world to prevent diseases, owing antioxidant, antimicrobial, anti-inflammatory and antitumor activities. The major component of Brazilian green propolis is Artepillin C (ArtC), a cinnamic acid derivative with two prenylated groups that improve the affinity of the compound for lipophilic environment. Here we have employed optical absorption and fluorescence techniques to draw conclusions on how ArtC interacts with amphiphilic aggregates commonly used as model membranes having different charges in the polar head group. Optical absorption spectra were representative of the protonation state of ArtC, dictated by the local pH at the surface of micelles and lipid vesicles. Fluorescence results Accepted Article This article is protected by copyright. All rights reserved. showed that, in the presence of micelles and vesicles, the polarizability around ArtC was modified, compared to the value in aqueous medium, and the molecule should be located preferentially on the surface region of the model membranes, with an enhanced interaction with the less ordered state of the lipid vesicles.
Food Science & Nutrition, 2019
Free radicals are atoms or molecules with unpaired electrons that are highly unstable and active ... more Free radicals are atoms or molecules with unpaired electrons that are highly unstable and active toward chemical reactions with other molecules. They are constantly created from cell metabolism and can lead to damage to proteins, lipids, RNA, and DNA, among other molecules (Chan, Gan, & Corke, 2016). An excess of free radicals is related to various severe diseases, including cancer, atherosclerosis, stroke, Alzheimer's, and Parkinson's, among others (Aruoma, 1998; Carocho & Ferreira, 2013). Antioxidants are substances able to prevent or inhibit oxidation processes in human body as well as in food product (Duda-Chodak & Tarko, 2007). Free radicals can be inhibited by antioxidants.
International Journal of Pharmaceutics, 2017
The sesquiterpene nerolidol and the monoterpene limonene are potent skin-permeation enhancers tha... more The sesquiterpene nerolidol and the monoterpene limonene are potent skin-permeation enhancers that have also been shown to have antitumor, antibacterial, antifungal and antiparasitic activities. Because terpenes are membrane-active compounds, we used electron paramagnetic resonance (EPR) spectroscopy of three membrane spin labels combined with the fluorescence spectroscopy of three lipid probes to study the interactions of these terpenes with stratum corneum (SC) intercellular membranes. An experimental apparatus was developed to assess the lipid fluidity of hydrated SC membranes via the fluorescence anisotropy of extrinsic membrane probes. Both EPR and fluorescence probes indicated that the intercellular membranes of neonatal SC rats undergo a main phase transition at approximately 50°C. Taken together, the results indicated that treatment with 1% nerolidol (v/v) caused large fluidity increases in the more ordered phases of SC membranes and that these effects gradually decreased with increasing temperature. Additionally, compared with (+)-limonene, nerolidol was better able to change the SC membrane dynamics. EPR and fluorescence data suggest that these terpenes act as spacers in lipid packaging and create increased lipid disorder in the more ordered regions and phases of SC membranes, notably leading to a population of probes with less restricted motion.
International journal of biological macromolecules, 2017
Glossoscolex paulistus extracellular hemoglobin (HbGp) stability has been followed, in the presen... more Glossoscolex paulistus extracellular hemoglobin (HbGp) stability has been followed, in the presence of urea, using fluorescein isothiocyanate (FITC). Binding of FITC to HbGp results in a significant quenching of probe fluorescence. Tryptophan emission decays present four characteristic lifetimes: two in the sub-nanosecond/picosecond, and two in the nanosecond time ranges. Tryptophan decays for pure HbGp and HbGp-FITC systems are similar. In the absence of denaturant, and up to 2.5mol/L of urea, the shorter lifetimes predominate. At 3.5 and 6.0mol/L of urea, the longer lifetimes increase significantly their contribution. Urea-induced unfolding process is characterized by protein oligomeric dissociation and denaturation of dissociated subunits. FITC emission decays for FITC-HbGp system are also multi-exponential with three lifetimes: two in the sub-nanosecond and one in the nanosecond range with a value similar to free probe in buffer. Increase of urea concentration leads to increase ...
Journal of Apicultural Research, 2017
Propolis is a bee product that results from the mixture of beeswax and resinous compounds. It can... more Propolis is a bee product that results from the mixture of beeswax and resinous compounds. It can scavenge free radicals; therefore, it displays antioxidant activity. Here, we have investigated the antioxidant potential of propolis produced by three Brazilian stingless bee species: Melipona quadrifasciata anthidiodes (Mandaçaia) and Tetragona clavipes (Borá), which inhabit the southeastern region of Brazil (state of São Paulo), and Scaptotrigona spp. (Tubi), which inhabits the northeastern region of Brazil (state of Maranhão). The antioxidant activities of propolis produced by different bee species were compared to the well-known antioxidant activity of green propolis, produced by the honey bee Apis mellifera. The ethanolic extract of propolis produced by Mandaçaia displayed the strongest antioxidant activity. The activity was even stronger than the antioxidant activity of green propolis. The ethyl acetate and aqueous fraction of propolis produced by Mandaçaia presented the highest antioxidant activity. This result agreed with the higher total polyphenol content verified in this propolis. high performance liquid chromatography analysis revealed that the groups of compounds present in propolis produced by Mandaçaia, Tubi, and Borá were not the same as those previously identified as the main constituents of green propolis. In fact, propolis produced by Mandaçaia contained many other polyphenols in the fingerprint, and hence its composition requires further elucidation. Actividad antioxidante de tres tipos de propó leos de abeja sin aguijó n y propó leos verdes El propó leos es un producto de abeja que resulta de la mezcla de cera de abejas y compuestos resinosos. Puede eliminar radicales libres; por lo tanto, muestra actividad antioxidante. En este trabajo se investigó el potencial antioxidante del propó leo producido por tres especies de abejas sin aguijó n: Melipona quadrifasciata anthidiodes (Mandaçaia) y Tetragona clavipes (Borá), que habitan la regió n sureste de Brasil (estado de São Paulo) y Scaptotrigona spp. (Tubi), que habita la regió n noreste de Brasil (estado de Maranhão). Las actividades antioxidantes del propó leos producido por diferentes especies de abejas fueron comparadas con la conocida actividad antioxidante del propó leos verde, producido por la abeja Apis mellifera. El extracto etanó lico de propó leos (EEP) producido por Mandaçaia mostró la mayor actividad antioxidante. La actividad fue aún más fuerte que la actividad antioxidante del propó leos verde. El acetato de etilo y la fracció n acuosa de propó leos producidos por Mandaçaia presentaron la mayor actividad antioxidante. Este resultado coincidió con el mayor contenido de polifenoles totales verificado en este propó leos. El análisis por HPLC reveló que los grupos de compuestos presentes en los propó leos producidos por Mandaçaia, Tubi y Borá no eran los mismos que los previamente identificados como los principales constituyentes del propó leos verde. De hecho, el propó leos producido por Mandaçaia contenía muchos otros polifenoles en la huella, y por lo tanto su composició n requiere una dilucidació n adicional.
Biochimica et biophysica acta, Apr 24, 2017
The study of Acridine Orange (AO) spectral characteristics and the quenching of its singlet and t... more The study of Acridine Orange (AO) spectral characteristics and the quenching of its singlet and triplet excited states by TEMPO radical at its binding to DNA in the function of the DNA concentration and in the absence and presence of NaCl is reported. The study was performed using steady-state and time resolved optical absorption and florescence, fluorescence correlation spectroscopy and resonant light scattering techniques. The presence of different species in equilibrium: AO monomers and aggregates bound to DNA, has been demonstrated, their relative content depending on the DNA and the AO concentrations. At high DNA concentration the AO monomers are protected against the contact with other molecules, thus reducing the AO excited state quenching. The addition of NaCl reduces the AO binding constant to DNA, thus reducing the AO and DNA aggregation. The interaction of AO with DNA is a complex process, including aggregation and disaggregation of both components. This modifies the AO e...
Journal of medicinal chemistry, Oct 26, 2016
The complexes cis-[Ru(phen)2(Apy)2](2+), Apy = 4-aminopyridine and 3,4-aminopyridine are stable i... more The complexes cis-[Ru(phen)2(Apy)2](2+), Apy = 4-aminopyridine and 3,4-aminopyridine are stable in aqueous solution with strong visible absorption. They present emission in the visible region with long lifetime that accumulates in the cytoplasm of Neuro2A cell line without appreciable cytotoxicity. The complexes also serve as mixed-type reversible inhibitors of human AChE and BuChE with high active site contact. cis-[Ru(phen)2(3,4Apy)2](2+) competes efficiently with DMPO by the OH(•) radical. Luminescence, using fluorescence lifetime imaging (FLIM), enables real-time imaging of the conformational changes of the self-aggregation of Aβ with incubation of complexes (0-24 hours) in phosphate buffer at micromolar concentrations. By this technique, we identified protofibrills in the self-assembly of Aβ1-40 and globularstructures in the short fragment Aβ15-21 in aqueous solution.
Applied spectroscopy, Jan 5, 2016
The parathyroid glands are small and often similar to lymph nodes, fat, and thyroid tissue. These... more The parathyroid glands are small and often similar to lymph nodes, fat, and thyroid tissue. These glands are difficult to identify during surgery and a biopsy of the parathyroid for identification can lead to damage of the gland. The use of static and time-resolved fluorescence techniques to detect biochemical composition and tissue structure alterations could help to develop a portable, minimally invasive, and nondestructive method to assist medical evaluation of parathyroid tissues. In this study, we investigated 10 human parathyroid samples by absorbance, fluorescence, excitation, and time-resolved fluorescence measurements. Moreover, we compared the results of time-resolved fluorescence measurements with 59 samples of thyroid tissues. The fluorescence lifetimes with emission at 340 nm were 1.09 ± 0.10 and 4.46 ± 0.06 ns for healthy tissue, 1.01 ± 0.25 and 4.39 ± 0.36 ns for benign lesions, and 0.67 ± 0.36 and 3.92 ± 0.72 ns for malignant lesions. The lifetimes for benign and mal...
Semina: Ciências Sociais e Humanas, 1982
Hyperfine Interactions, 1986
Journal of Biomedical Optics, 2015
Fine-needle aspiration cytology is the standard technique to diagnose thyroid pathologies. Howeve... more Fine-needle aspiration cytology is the standard technique to diagnose thyroid pathologies. However, this method results in a high percentage of inconclusive and false negatives. The use of time-resolved fluorescence techniques to detect biochemical composition and tissue structure alterations could help to develop a portable, minimally invasive, and nondestructive method to assist during surgical procedures. This study aimed to use fluorescence lifetimes to differentiate healthy and benign tissues from malignant thyroid tissue. The thyroid tissue was excited at 298-300 nm and the fluorescence decay registered at 340 and 450 nm. We observed fluorescence lifetimes at 340 nm emission of 0.80 AE 0.26 and 3.94 AE 0.47 ns for healthy tissue; 0.90 AE 0.24 and 4.05 AE 0.46 ns for benign lesions; and 1.21 AE 0.14 and 4.63 AE 0.25 ns for malignant lesions. For 450 nm emissions, we obtain lifetimes of 0.25 AE 0.18 and 3.99 AE 0.39 ns for healthy tissue, 0.24 AE 0.17 and 4.20 AE 0.48 ns for benign lesions, 0.33 AE 0.32 and 4.55 AE 0.55 ns for malignant lesions. Employing analysis of variance, we differentiate malignant lesions from benign and healthy tissues. In addition, we use quadratic discriminant analysis to distinguish malignant from benign and healthy tissues with an accuracy of 76.1%, sensitivity of 74.7%, and specificity of 83.3%. These results indicate that time-resolved fluorescence can assist medical evaluation of thyroid pathologies during surgeries.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2015
h i g h l i g h t s Simulation of the theoretical electronic absorption spectra of orthoaminobenz... more h i g h l i g h t s Simulation of the theoretical electronic absorption spectra of orthoaminobenzoic acid by TD-DFT. Use of microhydration and PCM models to obtain spectra in aqueous medium. Analysis of geometric properties as well as intermolecular and intramolecular hydrogen bonds. When more water molecules surround ortho-aminobenzoic acid, the spectrum resembles the experimental data more closely. Microhydration and PCM models are necessary to fit the spectrum correctly.
Biospectroscopy, 1998
ortho-Aminobenzoic acid (Abz) has been used as a convenient fluorescent donor group in internally... more ortho-Aminobenzoic acid (Abz) has been used as a convenient fluorescent donor group in internally quenched fluorescent peptides, which are employed as substrates for several proteolytic enzymes. As Abz is usually bound to the N-amino terminal of these peptides, it is of interest to investigate the Abz group fluorescent properties bound to different amino acids. We report in this article the optical absorption and fluorescent properties, in aqueous media, of Abz bound to the ␣-amino group of Ala, Gly, Leu, Ile, Val, Pro, Phe, Arg, Glu, Met, Asn, Tyr, and Trp, with monomethylamidated ␣-carboxyl group. In order to explore the origin of the drastic reduction of Abz attached to N ␣ amino group of prolyl-peptides, we also examined the fluorescence properties of Abz-NHCH 3 , Abz-N(CH 3) 2 , and Abz-pyrrolidine. Molecular dynamics simulation and NMR data indicated a lack of periplanarity of the Abz-dimethylamide, which could be the origin of low fluorescence quantum yield of Abz-prolyl-peptides.
Latin America Optics and Photonics Conference, 2010
Page 1. Excited State Studies in Ruthenium Porphyrins Using Z-Scan Technique RN Sampaio, NM Barbo... more Page 1. Excited State Studies in Ruthenium Porphyrins Using Z-Scan Technique RN Sampaio, NM Barbosa Neto Institute of Physics Federal University of Uberlândia João Naves de Ávila Avenue, 2121 - Santa Mônica - Uberlândia ...
Letters in Peptide Science, 1995
A general procedure, using the commonly employed solid-phase peptide synthesis methodology for ob... more A general procedure, using the commonly employed solid-phase peptide synthesis methodology for obtaining internally quenched fluorogenic peptides with ortho-aminobenzoyl/dinitrophenyl groups as donor-acceptor pairs, is presented. The essential feature of this procedure is the synthesis of an N~-Boc or-Fmoc derivative of glutamic acid with the a-carboxyl group bound to N-(2,4-dinitrophenyl)-ethylenediamine (EDDnp), which provides the quencher moiety attached to the C-terminus of the substrate. The fluorescent donor group, ortho-aminobenzoic acid (Abz), is incorporated into the resin-bound peptide in the last coupling cycle. Depending on the resin type used, Abz-peptidyl-Gln-EDDnp or Abz-peptidyl-Glu-EDDnp is obtained. Using the procedure described above, substrates for human renin and tissue kallikreins were synthesised. Spectrofluorimetric measurements of Abz bound to the a-amino group of proline showed that strong quenching of Abz fluorescence occurs in the absence of any acceptor group.