Curcumin ((1,7-bis-(4-hidroxi-3-metoxifenil)-1,6-heptadieno-3,5-diona)), is a natural yellow-orange polyphenol dye, obtained from Curcuma longa rhizomes, with vast potential in the biotechnology ...field, such as anti – inflammatory and cancer preventive properties, and a very environmental-sensible structure, mostly resulting in aggregate formations, with low solubility in aqueous solvents and remarkable pH dependence. Hence, it is essential to comprehend its aggregation mechanisms, optical properties and conformational equilibrium to develop curcumin-based drugs and biomaterials for several applications. With the purpose of understand such concepts and its properties, the results presented in this work, obtained through spectroscopic measurements and the Hill's modeling, show a conformational equilibrium, driven by pH, between the enol-enolate and aggregated forms in curcumin, and the respective energy transfer processes between these species. Additionally, the photophysical mechanisms for the energy transfer between aggregated forms, observed with the ellipsometry measurements, showed an “all-or-nothing” character, pointing to a very complex conformation for curcumin aggregates.
pH-driven conformational equilibrium between enol-enolate and aggregated forms in curcumin showing the “all-or-nothing” character for energy transfer photophysical mechanisms. Display omitted
•Basic pH promotes conformational equilibrium between enol-enolate and curcumin aggregated forms.•Coexisting with enol-enolate forms, curcumin showed, at least, two different aggregates species.•Energy transfer between enol-enolate and aggregated forms showed an “all-or-nothing” character.
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Stabilization and electrical contacting of redox enzymes with electrodes are fundamental requirements for bioelectronics devices, including biosensors and enzyme fuel cells (EFCs). In this study, we ...show increased glucose oxidase (GOx) stability by immobilization with Nafion. The immobilization process affected GOx conformation but was not detrimental to its activity, which was maintained for more than 120 days. The GOx/Nafion system was interfaced to a carbon cloth electrode and assembled in a prototypal EFC fed with glucose. Polarization and power density curves demonstrated that GOx/Nafion system was able to generate power, exploiting a Nafion-assisted electron transfer process to the electrode. Our findings are consistent with the onset of pH-dependent conformational equilibrium for the enzyme secondary structure and its active site. Significantly, the protective effect exerted by Nafion on the enzyme structure may be tuned by varying parameters such as the pH to fabricate durable EFCs with good electrocatalytic performance.
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Epoxide hydrolases (EHs) are enzymes that are present in all living organisms and catalyze the hydrolysis of epoxides to the corresponding vicinal diols. EHs have biotechnological potential in chiral ...chemistry. We report the cloning, purification, enzymatic activity, and conformational analysis of the TrEH gene from Trichoderma reesei strain QM9414 using circular dichroism spectroscopy. The EH gene has an open reading frame encoding a protein of 343 amino acid residues, resulting in a molecular mass of 38.2kDa. The enzyme presents an optimum pH of 7.2, and it is highly active at temperatures ranging from 23 to 50°C and thermally inactivated at 70°C (t1/2=7.4min). The Michaelis constants (Km) were 4.6mM for racemic substrate, 21.7mM for (R)-(+)-styrene oxide and 3.0mM for (S)-(−)-styrene oxide. The kcat/Km analysis indicated that TrEH is enantioselective and preferentially hydrolyzes (S)-(−)-styrene oxide. The conformational stability studies suggested that, despite the extreme conditions (high temperatures and extremely acid and basic pHs), TrEH is able to maintain a considerable part of its regular structures, including the preservation of the native cores in some cases. The recombinant protein showed enantioselectivity that was distinct from other fungus EHs, making this protein a potential biotechnological tool.
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The use of ultraviolet (UV) and blue irradiation to sterilize surfaces is well established, but commercial applications would be enhanced if the light source is replaced with ambient light. In this ...paper, it is shown that nanofibers can be explored as an alternative methodology to UV and blue irradiation for bacterial inactivation. It is demonstrated that this is indeed possible using spun nanofibers of polylactic-co-(glycolic acid) (PLGA). This work shows that PLGA spun scaffolds can promote photoinactivation of Staphylococcus aureus and Escherichia coli bacteria with ambient light or with laser irradiation at 630 nm. With the optimized scaffold composition of PLGA85:15 nanofibers, the minimum intensity required to kill the bacteria is much lower than in antimicrobial blue light applications. The enhanced effect introduced by PLGA scaffolds is due to their nanofiber structures since PLGA spun nanofibers were able to inactivate both S. aureus and E. coli bacteria, but cast films had no effect. These findings pave the way for an entirely different method to sterilize surfaces, which is less costly and environmentally friendly than current procedures. In addition, the scaffolds could also be used in cancer treatment with fewer side effects since photosensitizers are not required.
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5.
Ellipsometric Raman Spectroscopy Basilio, Fernando C; Campana, Patricia T; Therézio, Eralci M ...
Journal of physical chemistry. C,
11/2016, Volume:
120, Issue:
43
Journal Article
Peer reviewed
We introduce a new experimental technique referred to as ellipsometric Raman spectroscopy (ERS) to quantify the Raman optical activity (ROA) where ellipsometry is combined with Raman spectroscopy. ...The Stokes parameters were determined for Raman scattered light using Fourier decomposition in measurements with achromatic optical components in a nine-point method. We tested the methodology with ultrapure water, a well-known chiral alcohol, and a chiral polymer, and we show that ERS allows for studying not only the vicinities of chiral carbons but also molecular species coupled to form chiral structures. Furthermore, in ERS, isotropic and anisotropic scattering contribute equally, thus making it possible to analyze the low-wavenumber region in samples such as the chiral polymer studied here, for which the ROA signal probably arises mainly from isotropic scattering.
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The present paper deals with the isolation and purification of a new sialic acid binding lectin from the seed integument of Saraca indica (Ashok) and the purified lectin was designated Saracin II. ...Comparative studies on the interactions of saracin II and another sialic acid specific lectin Sambucus nigra agglutinin (SNA) with N-acetylneuraminic acid (NANA) were made using UV–vis absorption, steady state and time resolved fluorescence along with circular dichroism (CD) spectroscopy to reveal the nature and mechanisms of binding of these two lectins with NANA. The experimental observations obtained from UV–vis, steady state and time resolved fluorescence measurements demonstrated that SNA–NANA system formed relatively stronger ground state complex than saracin II–NANA pair. CD measurements further substantiated the propositions made from steady state and time resolved spectroscopic investigations. It was inferred that during interaction of SNA with NANA, the lectin adopted a relatively looser conformation with the extended polypeptide structures leading to the exposure of the hydrophobic cavities which favoured stronger binding with NANA.
•Of the two lectins, stronger binding of SNA with NANA is observed.•Full exposure of the hydrophobic cavities of SNA favors the stronger interactions.•Saracin II can be used for the new generation of lectin based-therapeutics.
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The catalytic behaviour of alpha-CT (alpha-chymotrypsin) is affected by cationic micelles of CTABr (hexadecyltrimethylammonium bromide). The enzyme-micelle interaction leads to an increase in both ...the V(max) and the affinity for the substrate p -nitrophenyl acetate, indicating higher catalytic efficiency for bound alpha-CT. The bell-shaped profile of alpha-CT activity with increasing CTABr concentrations suggests that the micelle-bound enzyme reacts with the free substrate. Although more active with CTABr micelles, the enzyme stability is essentially the same as observed in buffer only. Enzyme activation is accompanied by changes in alpha-CT conformation. Changes in tertiary structure were observed by the increase in intensity and the red shift in the alpha-CT tryptophan fluorescence spectrum, suggesting the annulment of internal quenching and a more polar location of tryptophan residues. Near-UV CD also indicated the transfer of aromatic residues to a more flexible environment. CTABr micelles also induces an increase in alpha-helix, as seen by far-UV CD and FTIR (Fourier-transform infrared) spectroscopies. The far-UV CD spectrum of alpha-CT shows an increase in the intensity of the positive band at 198 nm and in the negative band at 222 nm, indicating an increased alpha-helical content. This is in agreement with FTIR studies, where an increase in the band at 1655 cm(-1), corresponding to the alpha-helix, was shown by fitting analysis and difference spectroscopy. Spectral deconvolution indicated a reduction in the beta-sheet content in micelle-bound alpha-CT. Our data suggest that the higher catalytic efficiency of micelle-bound alpha-CT results from significant conformational changes.
Angiotensin II (AII) is the active octapeptide product of the renin enzymatic cascade, which is responsible for sustaining blood pressure. In an attempt to establish the AII-receptor-bound ...conformation of this octapeptide, we designed conformationally constrained analogues by scanning the entire AII sequence with an i-(i+2) and i-(i+3) lactam bridge consisting of an Asp-(Xaa)n-Lys scaffold. Most analogues presented low agonistic activity when compared to AII in the different bioassays tested. The exceptions are cyclo(0-1a) Asp0, endo-(Lys1a)-AII (1) and Asp0, endo-(Lys1a)-AII (2), both of which showed activity similar to AII. Based on peptide 1 and the analogue cyclo(3–5)Sar1, Asp3, Lys5-AII characterized by Matsoukas et al., we analyzed the agonistic and antagonistic activities, respectively, through a new monocyclic peptide series synthesized by using the following combinations of residues as bridgehead elements for the lactam bond formation: D- or L-Asp combined with D- or L-Lys or L-Glu combined with L-Orn. Six analogues showed an approximately 20% increase in biological activity when compared with peptide (1) and were equipotent to AII. In contrast, six analogues presented antagonistic activity. These results suggest that the position of the lactam bridge is more important than the bridge length or chirality for recognition of and binding to the angiotensin II AT1-receptor.
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We report the simultaneous observations of the prompt emission in the gamma-ray and hard X-ray bands by the Swift BAT and the Konus-Wind instruments of the short-hard burst, GRB 060313. The ...observations reveal multiple peaks in both the gamma-ray and hard X-ray bands suggesting a highly variable outflow from the central explosion. We also describe the early-time observations of the X-ray and UV/optical afterglows by the Swift XRT and UVOT instruments. The combination of the X-ray and UV/optical observations provides the most comprehensive light curves to date of a short-hard burst at such an early epoch. The afterglows exhibit complex structure with different decay indices and flaring. This behavior can be explained by the combination of a structured jet, radiative loss of energy, and decreasing microphysics parameters occurring in a circumburst medium with densities varying by a factor of approximately two on a length scale of 10 super(17) cm. These density variations are normally associated with the environment of a massive star and inhomogeneities in its windy medium. However, the mean density of the observed medium (n610 super(4) cm super(3)) is much less than that expected for a massive star. Although the collapse of a massive star as the origin of GRB 060313 is unlikely, the merger of a compact binary also poses problems for explaining the behavior of this burst. Two possible suggestions for explaining this scenario are that some short bursts may arise from a mechanism that does not invoke the conventional compact binary model, or that soft late-time central engine activity is producing UV/optical but no X-ray flaring.
The data presented in this article are related to the research article entitled “Epoxide hydrolase of Trichoderma reesei: Biochemical properties and conformational characterization” 1. Epoxide ...hydrolases (EHs) are enzymes that catalyze the hydrolysis of epoxides to the corresponding vicinal diols. This article describes the optimal parameters for the colorimetric red assay to determine the enzymatic activity, with an emphasis on the characterization of the kinetic parameters, pH optimum and thermal stability of this enzyme. The effects of reagents that are not resistant to oxidation by sodium periodate on the reactions can generate false positives and interfere with the final results of the red assay.
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