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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]

Laccases are multicopper oxidases which oxidize a wide variety of aromatic compounds with the concomitant reduction of oxygen to water as by-product. Due to their high stability and biochemical versatility, laccases are key enzymes to be used as eco-friendly biocatalyst in biotechnological applications. The presence of copper paramagnetic species in the catalytic site paired with the substrate radical species produced in the catalytic cycle makes laccases particularly attractive to be studied by spectroscopic approaches. In this review, the potentiality of a combined multifrequency electron paramagnetic spectroscopy /computational approach to gain information on the nature of the catalytic site and radical species is presented. The knowledge at molecular level of the enzyme oxidative process can be of great help to model new enzymes with increased efficiency and robustness. [ABSTRACT FROM AUTHOR]

The antioxidant properties of galloyl quinic derivatives isolated from Pistacia lentiscus L. leaves have been investigated by means of Electron Paramagnetic Resonance spectroscopy (EPR) and UV-Vis spectrophotometry. Antioxidant properties have been also estimated using the biologically relevant LDL test. The scavenger activities of gallic acid, 5-O-galloyl, 3,5-Ο-digalloyl, 3,4,5-Ο-trigalloyl quinic acid derivatives, have been estimated against 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, superoxide (O[sub2][sup-]) radical, and hydroxyl (OH) radical. On the whole, the scavenger activity raised as the number of galloyl groups on the quinic acid skeleton increased. The half-inhibition concentrations (IC[sub50]) of di- and tri-galloyl derivatives did not exceed 30 μM for all the tested free radicals. All the tested metabolites strongly reduced the oxidation of low-density lipoproteins (LDL), following a trend similar to that observed for the scavenger ability against OH radical. [ABSTRACT FROM AUTHOR]

An actinobacteria strain was isolated from Algerian Sahara soil and assigned to Streptomyces cyaneofuscatus Pridham et al. 1958 species. This strain was selected for its ability to produce melanin exopigments in liquid and solid media. Melanin synthesis was associated with tyrosinase activity and the enzyme from this strain was isolated and biochemically characterized. Synthetic melanin was then enzymatically produced using the S. cyaneofuscatus Pridham et al. 1958 tyrosinase. As this enzyme showed a higher diphenolase activity, a synthetic melanin from the enzymic oxidation of 3,4-dihydroxyphenylalanine (dopa) was obtained by the use of a Trametes versicolor (L.) Lloyd laccase for comparison. The natural and synthetic pigments were physico-chemically characterized by the use of ultraviolet (UV)-Visible, and Fourier transform infrared (FT-IR) and multifrequency electron paramagnetic resonance (EPR) spectroscopies. All the melanin samples displayed a stable free radical when analyzed by X-band EPR spectroscopy. Once the samples were recorded at Q-band EPR, a copolymer derived from a mixture of different constituents was evident in the natural melanin. All radical species were analyzed and discussed. The use of water-soluble melanin naturally produced by S. cyaneofuscatus Pridham et al. 1958 represents a new biotechnological alternative to commercial insoluble pigments. [ABSTRACT FROM AUTHOR]

In the slow-motion region, ESR spectra cannot be expressed as a sum of simple Lorentzian lines. Studies of Freed and co-workers, on nitroxides in liquids gained information on the microscopic models of rotational dynamics, relying much on computer programs for simulation of ESR spectra based on the stochastic Liouville equation (SLE). However, application of Freed’s method to copper system of biological interest has been for a long time precluded by lack of a full program able to simulate ESR spectra containing more than one hyperfine interaction. Direct extension of the Freed’s approach in order to include superhyperfine interaction is not difficult from a theoretical point of view but the resulting algorithm is problematical because it leads to substantial increase in the dimensions of the matrix related to the spin-hamiltonian operator. In this paper preliminary results of a new program, written in C, which includes the superhyperfine interactions are presented. This preliminary version of the program does not take into account a restoring potential, so it can be used only in isotropic diffusion conditions. A comparison with an approximate method previously developed in our laboratory, based on a post-convolution approach, is discussed. [Copyright &y& Elsevier]

In order to show the importance of conformation of the amino acid side-chains on water binding or water release to the copper(II) in complexes with long aliphatic side-chains, the temperature dependence of Brownian motion of the bis[N,N-dimethyl-l-α-alaninato]copper(II) complex compared with the bis[N,N-dimethyl-l-α-isoleucinato]copper(II) complex dissolved in deuterated methanol is analyzed. The hypothesis is that binding or release of the water molecule from copper(II) in the complex with N,N-dimethyl-l-α-isoleucine may be related to the conformation change of the amino acid side-chains. In the case of bis[N,N-dimethyl-l-α-alaninato]copper(II) the conformation change of the amino acid side-chains (&z.sbnd;CH3) is not possible. If the copper(II) complex retains one conformation in the examined temperature interval, the reorientation correlation time τ2, describing the Brownian motion of the complex will be a linear function of η/T, as is obtained for bis[N,N-dimethyl-l-α-alaninato]copper(II). In the whole temperature interval measured (276–332 K), the electron paramagnetic resonance (EPR) spectra are fitted well with characteristic parameters for the complex with bound water. For bis[N,N-dimethyl-l-α-isoleucinato]copper(II) more complex temperature dependence of τ2 on η/T is obtained. Above 300 K, the EPR spectra could not be fitted with the parameters of the complex with bound water, but are fitted well with the parameters characteristic for a copper(II) complex that does not contain an apical water molecule. [Copyright &y& Elsevier]