Production Of Carbonyl Groups Research Articles

Production of carbonyl groups in the plasma of neonates is inversely associated with gestational age and O2 requirement

Production of carbonyl groups in the plasma of neonates is inversely associated with gestational age and O2 requirement

Anti-Yellowing Property of Polyurethane Improved by the Use of Surface-Modified Nanocrystalline Cellulose

Nanocrystalline cellulose (NCC) was used to improve the anti-yellowing property of polyurethane (PU). The NCC was modified with 3-glycidoxypropyltrimethoxysilane (GPTMS) to enhance its compatibility with PU, and the surface-modified NCC was characterized by contact angle (CA), X-ray powder diffraction (XRD), and thermogravimetric analysis (TG). NCC/PU composite was examined by scanning electron microscopy (SEM), Fourier transform infrared spectrophotometer (FT-IR), and X-ray photoelectron spectroscopy (XPS). Anti-yellowing property of the NCC/PU composite was determined using the Chinese National Standard GB/T 23999-2009. The results showed that the CA between modified NCC and PU was decreased by 26.6% (with 8% GPTMS). The crystal structure of NCC was inconspicuously affected by the surface modification, while the thermal stability of modified NCC was enhanced by 5.5%. The surface-modified NCC particles were homogeneously dispersed in the PU (as shown in the SEM micrographs). FT-IR and O1s XPS survey spectra of NCC/PU composites indicated the oxidation of hydroxyl groups and the production of carbonyl groups, while the photochemical degradation of PU resulting from UV radiation was prevented by the addition of NCC. The anti-yellowing property of the NCC/PU composite with 1.5% surface-modified NCC was increased by 57.7% and the contribution was decreased when the content of modified NCC was 2.0%.

Acetylation of wood causes photobleaching

This paper deals with the photobleaching of acetylated wood. The acetylated spruce wood was irradiated by artificial sunlight emitted from xenon lamp with covering several kinds of band-pass filter. The lightness ( L *) of acetylated wood increased with integral irradiance. The chroma (Δ C *) decreased by light-irradiation with wavelength from 430 nm to 500 nm. However, the light-irradiation including ultraviolet ray region made it decrease after increase with integral irradiance. The visible light made hue angle ( h°) increase, however, the ultraviolet ray made it decrease. The lignin degradation and the production of carbonyl groups were observed by light-irradiation including ultraviolet ray. However, no remarkable changes in IR spectra were observed by visible light-irradiation. Photobleaching of acetylated wood was caused by mainly visible light without modifying the IR spectra of lignin.

Degradation Studies of Polyurethanes Based on Vegetable Oils. Part 2. Thermal Degradation and Materials Properties

Polyurethanes (PUs), produced by cross-linking with a di-isocyanate hydroxylated vegetable oils (rapeseed and sunflower), have been examined from the viewpoints of their thermal degradation and their materials properties, and how both of these aspects are influenced both by the addition of TiO2 filler and by UV irradiation. The thermal decomposition of the PUs was investigated using thermal gravimetric analysis (TGA) and IR spectroscopy: the decomposition of a foam of the PU based on rapeseed oil showed complex kinetics, being apparently single-stage and of the first order at 973 K but with at least two separate stages at other temperatures. Thermolysis of PUs as films resulted in the production of carbonyl groups ( v 1793 cm−1) suggesting formation of an acid anhydride. Pyrolysis in vacuo produced volatiles which could be separated and examined by IR and NMR spectroscopy. Reaction mechanisms for the thermal decomposition of the PUs are proposed. The materials properties of the PUs, with and without TiO2 filler, have been examined by differential scanning calorimetry (DSC), dynamical mechanical thermal analysis (DMTA), tensile testing and measurement of scratch resistance and Shore D hardness. Addition of TiO2 improves systematically the scratch resistance and hardness of the PUs, but the glass transition temperature Tg showed a more complicated dependence on the TiO2 loading, initially falling and then increasing. Prolonged UV irradiation of TiO2-loaded samples increased the value of Tg at all loadings, suggesting increased levels of cross-linking on irradiation. The most dramatic effect of adding TiO2 was on the shape of the stress-strain curves: at 10% loading clear ‘soft-but-tough’ behaviour is evident. The values of tan δ and the storage modulus are also strongly affected by addition of TiO2, with and without UV-irradiation. From the viewpoint of utilisation of these PUs, their thermal stability up to 350°C and the beneficial effects of adding TiO2 make them promising materials.

A fluorescence study of human serum albumin binding sites modification by hypochlorite

A study has been made on the properties of human serum albumin (HSA) binding sites and how they are modified by pre-oxidation of the protein with hypochlorite. The oxidation extent was assessed from changes in the protein intrinsic fluorescence and production of carbonyl groups. HSA retains its solute binding capacity even after exposure to relatively large amounts of hypochlorite (up to 40 oxidant molecules per protein). From an analysis of the binding isotherms of dansyl sarcosine (DS) and dansyl-1-sulfonamide (DNSA) to native and hypochlorite treated albumin it is concluded that pre-oxidation of the protein reduces the number of active sites without affecting the binding capacity of the remaining binding sites. From DS and DNSA fluorescence anisotropy, Laurdan anisotropy and generalized polarization measurements, it is concluded that both Sites I and II in the native protein provide very rigid environments to the bound probes. These characteristics of the sites remain even after extensive treatment with hypochlorite. This stubbornness of HSA could allow the protein to maintain its function along its in vivo lifetime.

NADPH-initiated cytochrome P450-mediated free metal ion-independent oxidative damage of microsomal proteins. Exclusive prevention by ascorbic acid.

In this paper we demonstrate that NADPH-initiated oxidative damage of microsomal proteins occurs in the absence of free metal ions and that this protein oxidation is mediated by cytochrome P450 (cyt P450). Oxidized proteins are rapidly degraded by proteases. Ascorbate (AH2) specifically inhibits free metal ion-independent cyt P450-mediated protein oxidation and thereby prevents subsequent proteolytic degradation. Other scavengers of reactive oxygen species including superoxide dismutase, catalase, and glutathione are ineffective. This is in variance with free metal ion-catalyzed protein oxidation, which is accelerated by AH2 and inhibited by catalase. Oxidative damage of proteins has been assessed by the production of carbonyl groups, bityrosine formation, and tryptophan loss. The mechanism of protein oxidation has been studied using a reconstituted system comprised of purified NADPH-cyt P450 reductase, cyt P450, and isolated microsomal proteins as well as model polypeptides, e.g. poly-L-proline and poly-L-lysine. Cyt P450 Fe3+ is reduced by NADPH-cyt P450 reductase to cyt P450 Fe2+, which consumes oxygen in a stoichiometric proportion to produce cyt P450 Fe2+ O2, the resonance form of which is a perferryl moiety, cyt P450 Fe3+.O2-.. It is proposed that cyt P450 Fe3+.O2-. abstracts hydrogen from amino acid side chains leading to the production of carbonyl derivatives. Tentatively, AH2 prevents protein oxidation by interacting with cyt P450 Fe3+.O2-..

The effects of gamma-irradiation on thermally stimulated discharge current spectra in low-density polyethylene

An investigation has been made of permanent effects of γ-radiation on additive-free low-density polyethylene (LDPE) using thermally stimulated discharge current techniques (TSDC) over the temperature range -100–100°C. In the low temperature regime (-100–0°C) a peak occurring around -30°C was introduced by irradiation in air but not in oxygen-free nitrogen. It was found that this peak is due to dipole orientation of oxidation products such as carbonyl groups. The movement of the peak towards higher temperatures with increasing radiation absorbed dose, is explained in terms of radiation-induced crosslinking which increases with increasing dose. In the high temperature region, (0–100°C) a peak observed at approx. 45°C in pristine samples, is due to the release of charge carriers injected from the electrodes. This peak was marked in irradiated samples by charge carriers created by the radiation. In the latter case, a peak occurred in the temperature range 60–100°C depending on dose and polarisation voltage. This behaviour can be explained by assuming that irradiation in air introduces shallow traps within the material which can be filled from deeper traps by a field assisted process during repeated polarisations associated with successive measurements. The process does not occur for irradiation in nitrogen and it is suggested that the shallow trapping levels are the result of oxidation, particularly with the production of carbonyl groups.