Search

Known for its tunable conductivity and stability, Polyaniline (PANI) is a valuable polymer for electronics and sensing devices. Challenges in solubility have been addressed by creating sulfonated PANI (SPANI), enhancing its practical use. Synthesizing SPANI from sulfonated aniline is intricate, but laccase biocatalysis offers an eco-conscious solution, effective even against high redox potential obstacles. This research monitored the Trametes versicolor laccase-induced oxidation of 3-ABSa via UV-vis spectroscopy, with a notable peak at 565 nm signifying SPANI synthesis, effective even at suboptimal pH. Mediators further boost this process. Moreover, NMR and spectroelectrochemistry confirm the green synthesis of SPANI by laccase, hinting that pH fine-tuning could improve yields, alongside the concurrent creation of azobenzene derivatives. [ABSTRACT FROM AUTHOR]

The reaction of H2O2 with the enzyme in the absence of substrate is investigated with electron paramagnetic resonance (EPR) spectroscopy. The analysis of the versatile peroxidase (VP) from Bjerkandera adusta shows the presence of a tryptophan residue near to the heme prosthetic group, which is solvent-exposed as in the case of lignin peroxidase (LiP) and other VPs.

The synthetic peptide encompassing residues 106-126 of the human prion protein was considered for its binding properties toward copper(II), manganese(II) and zinc(II) at pH 5.7. The metal-peptide association was described by the paramagnetic effects of Cu(II) and Mn(II) upon 1D and 2D spectra, while Zn (II) was found to yield negligible effects upon any NMR parameter.

Glycated human serum albumin (gHSA) undergoes conformational changes and unfolding events caused by free radicals. The glycation process results in a reduced ability of albumin to act as an endogenous scavenger and transporter protein in diabetes mellitus type 2 (T2DM) patients. Astaxanthin (ASX) in native form and complexed with metal ions (Cu2+ and Zn2+) has been shown to prevent gHSA from experiencing unfolding events. Furthermore, it improves protein stability of gHSA and human serum albumin (HSA) as it is shown through molecular dynamics studies. In this study, the ASX/ASX-metal ion complexes were reacted with both HSA/gHSA and analyzed with electronic paramagnetic resonance (EPR) spectroscopy, rheology and zeta sizer (particle size and zeta potential) analysis, circular dichroism (CD) spectroscopy and UV-Vis spectrophotometer measurements, as well as molecular electrostatic potential (MEP) and molecular docking calculations. The addition of metal ions to ASX improves its ability to act as an antioxidant and both ASX or ASX-metal ion complexes maintain HSA and gHSA stability while performing their functions. [ABSTRACT FROM AUTHOR]

Research has been conducted on the macrocycles which contain cyanomethyl and aminomethyl side chains. The interaction of these compounds with Cu(II) cations have been investigated via the use of (super)1 H NMR and EPR spectrometry and the results are reported.

The structural determinants underlying the instability of plant peroxidases toward H2O2 are unknown. The reaction of the catalytically productive radical Fe(IV)＝O species with excess H2O2 generates a species named compound III, which is known to decay partitioning between ground state restoration and inactivation following catalytical suicide kinetics. To elucidate the structural changes involved in compound III formation and decay, here we report the characterization of two plant peroxidases using catalytic and spectroscopic characterization. Resonance Raman and EPR characterizations reveal that the structure of compound III is more related to the hydroxyl form of other heme proteins and not to the peroxyferryl form as has been previously suggested. [ABSTRACT FROM AUTHOR]

The International Journal of Molecular Sciences has published a special issue on the biotechnological applications of oxidoreductases. Oxidoreductases are enzymes that catalyze redox reactions and have industrial relevance in various fields such as chemical synthesis, fine chemical production, and the development of biomaterials. The special issue covers different aspects of research on oxidoreductases, including the discovery of novel enzymes, structure-activity relationship studies, and their applications in various industries. The use of oxidoreductases in biocatalytic reactions offers shorter reaction routes and potentially reduced environmental impact compared to traditional methods. [Extracted from the article]

Research determined the molecular arrangements of two copper(II) dipeptide complexes with the use of the combined electron paramagnetic resonance spectroscopy, second derivative displays and computer simulation techniques. The ionic and covalent nature of the metal-ligand bonds of the two copper dipeptides, Cu-GlyHis and CuHisGly complexes, are also examined. Results show two different dipeptide arrangements in the first coordination sphere. The combined approaches was also found to be effective in identifying a set of spin Hamiltonian input parameters for the copper dipeptides.

A spin labeling technique coupled with electron paramagnetic resonance (EPR) and circular dichroism (CD) were used to study the structure and dynamics of Humanin (HN) neuroprotective peptide in solution and for the first time in the presence of model cerebral cortex membranes (CCM). The results provide insight into great tendency of HN to aggregate even at low concentrations in water solutions at different ionic strengths and monomerizes in the TFE apolar environment.

Cistus incanus (Cistaceae) is a Mediterranean evergreen shrub. Cistus incanus herbal teas have been used as a general remedy in traditional medicine since ancient times. Recent studies on the antioxidant properties of its aqueous extracts have indicated polyphenols to be the most active compounds. However, a whole chemical characterisation of polyphenolic compounds in leaves of Cistus incanus (C. incanus) is still lacking. Moreover, limited data is available on the contribution of different polyphenolic compounds towards the total antioxidant capacity of its extracts. The purpose of this study was to characterise the major polyphenolic compounds present in a crude ethanolic leaf extract (CEE) of C. incanus and develop a method for their fractionation. Superoxide anion, hydroxyl and DPPH (1,1-diphenyl-2-picrylhydrazyl) radical scavenging assays were also performed to evaluate the antioxidant properties of the obtained fractions. Three different polyphenolic enriched extracts, namely EAC (Ethyl Acetate Fraction), AF1 and AF2 (Aqueos Fractions), were obtained from CEE. Our results indicated that the EAC, enriched in flavonols, exhibited a higher antiradical activity compared to the tannin enriched fractions (AF1 and AF2). These findings provide new perspectives for the use of the EAC as a source of antioxidant compounds with potential uses in pharmaceutical preparations. [ABSTRACT FROM AUTHOR]

ABSTRACT New photocatalytic fibers made of sulfonated polyetheretherketone (SPEEK)/polypropylene (PP) are melt compounded and melt spun, first on laboratory scale and then on a semi-industrial scale. Fiber spinnability is optimized and the fibers are characterized using mechanical testing, electron paramagnetic resonance (EPR) spectroscopy, and scanning electron microscopy (SEM). According to the results, the fiber spinnability remains at a good level up to 10 wt % SPEEK concentration. Optimal processing temperature is 200°C due to the thermal degradation at higher temperatures. EPR measurements show good and long-lasting photoactivity after the initial irradiation but also decay in the radical intensity during several irradiation cycles. Mechanical tenacity of the SPEEK/PP 5:95 fiber is approximately 20% lower than for otherwise similar PP fiber. The fiber is a potential alternative to compete against TiO2-based products but more research needs to be done to verify the real-life performance. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42595. [ABSTRACT FROM AUTHOR]

The mechanisms of industrial dye transformation by versatile peroxidase were elucidated. Purified versatile peroxidase from Bjerkandera adusta was able to decolorize different classes of dyes including azo and phthalocyanines, but unable to transform any of the anthraquinones tested. Kinetic constants for selected dyes were determined and the transformation products were analyzed by EPR spectroscopy and mass spectrometry. The EPR and MS analyses of the enzymatic decolorization products showed the cleavage of the azo bond in azo dyes and the total disruption of the phthalocyaninic ring in phthalocyanine dyes. The EPR analysis on two copper-containing dyes, reactive violet 5 (azo) and reactive blue 72 (phthalocyanine), showed that the transformation can or not break the metal-ion coordination bond according the dye nature. The role of the catalytic Trp172 in the dye transformation by a long-range electron transfer pathway was confirmed and the oxidation mechanisms are proposed and discussed. [ABSTRACT FROM AUTHOR]

Dye-decolorizing peroxidase (DyP) of Auricularia auricula-judae has been expressed in Escherichia coli as a representative of a new DyP family, and subjected to mutagenic, spectroscopic, crystallographic and computational studies. The crystal structure of DyP shows a buried haem cofactor, and surface tryptophan and tyrosine residues potentially involved in long-range electron transfer from bulky dyes. Simulations using PELE (Protein Energy Landscape Exploration) software provided several binding-energy optima for the anthraquinone-type RB19 (Reactive Blue 19) near the above aromatic residues and the haem access-channel. Subsequent QM/MM (quantum mechanics/molecular mechanics) calculations showed a higher tendency of Trp-377 than other exposed haem-neighbouring residues to harbour a catalytic protein radical, and identified the electron-transfer pathway. The existence of such a radical in H2O2-activated DyP was shown by low-temperature EPR, being identified as a mixed tryptophanyl/tyrosyl radical in multifrequency experiments. The signal was dominated by the Trp-377 neutral radical contribution, which disappeared in the W377S variant, and included a tyrosyl contribution assigned to Tyr-337 after analysing the W377S spectra. Kinetics of substrate oxidation by DyP suggests the existence of high- and low-turnover sites. The high-turnover site for oxidation of RB19 (kcat> 200 s-1) and other DyP substrates was assigned to Trp-377 since it was absent from the W377S variant. The low-turnover site/s (RB19 kcat ~20 s-1) could correspond to the haem access-channel, since activity was decreased when the haem channel was occluded by the G169L mutation. If a tyrosine residue is also involved, it will be different from Tyr-337 since all activities are largely unaffected in the Y337S variant. [ABSTRACT FROM AUTHOR]

ABSTRACT Sulfonated polyetheretherketone (SPEEK) was synthesized via a mono-substitution reaction of PEEK in concentrated sulphuric acid and was blended with polypropylene (PP) in 2-10%w/w concentration to be used for the production of photoactive thermoplastic products. SPEEK and SPEEK/PP blends were characterized using FTIR, DSC, TGA, NMR, rheology, SEM, and EPR. Under UV-Vis irradiation, stable benzophenone ketyl (BPK) radicals were generated by hydrogen extraction from PP. By increasing the amount of SPEEK in the polymer blend a linear increase in the BPK radicals was achieved according to the EPR data. DSC and TGA tests indicated weaknesses in the thermal stability of SPEEK but according to the rheological tests this should not have a major effect on processabililty. The optimal amount of SPEEK in the blend was obtained at 5%w/w. This concentration provided a good compromise between radical concentration, material processability, and cost. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41509. [ABSTRACT FROM AUTHOR]

Quantum mechanics/molecular mechanics molecular dynamics simulations have been used to predict the hydrogen-bonding networks in the active site of three double variants ofPleurotus eryngiiversatile peroxidase containing a redox-active tyrosine in place of a tryptophan residue in position 164. The adopted computational strategy has proved to be adequate to correctly reproduce the hydrogen-bonding environment of tyrosyl radical (Tyr√) in the single W164Y variant of the enzyme that has been directly identified by electron paramagnetic resonance spectroscopy. In this study, we have investigated the effect of the mutation of a specific amino acid in the local environment of tyrosine 164. We show that the substitution of arginine 257 with a glutamic acid, a leucine or an alanine residue is able to induce the stabilisation of different hydrogen-bonding networks involving Tyr√that can potentially affect its physico-chemical properties. [ABSTRACT FROM PUBLISHER]