Identification of low level gamma-irradiation of meats by high sensitivity comet assay

The detection of low levels of irradiation in meats (pork, beef, and chicken) using the new comet assay was investigated in order to assess the capability of the procedure. The new assay includes a process that improves its sensitivity to irradiation and a novel evaluation system for each slide (influence score and comet-type distribution). Samples used were purchased at retailers and were irradiated at 0.5 and 2 kGy at 0°C. The samples were processed to obtain comets. Slides were evaluated by typing comets, calculating the influence score and analyzing the comet-type distribution chart of shown on the slide. Influence scores of beef, pork, and chicken at 0 kGy were 287(SD=8.0), 305 (SD=12.9), and 320 (SD=21.0), respectively. Those at 500 Gy, were 305 (SD=5.3), 347 (SD=10.6), and 364 (12.6), respectively. Irradiation levels in food were successfully determined. Sensitivity to irradiation differed among samples (chicken>pork>beef).     

Study of antioxidant properties of flavonoids by voltammetry

Flavonoids are a large group of natural phenolic compounds contained in high concentrations in vegetables, fruits, etc. Antioxidant and redox properties of some flavonoids such as catechin, quercetin, dihydroquercetin, and rutin were investigated in this work. Optimal concentration and time of action of flavonoids were obtained. To determine the more effective range of antioxidant activity, mathematical models and the response surfaces of investigated flavonoids were determined using methods of experiment design. Oxidation potentials of the compounds were also obtained, E?=?0.3?÷?0.4?V. Moreover, the antioxidant activity of flavonoids depends on the redox properties and the structure of the flavonoids. The antioxidant activity of flavonoids, which is correlated to reversible potentials for this compound is good. Finally, the use of these substances as antioxidants with therapeutic effects has been recommended in human diet.     

The effect of high dose of gamma-irradiation on residual radicals concentration in ultra-high molecular weight polyethylene (UHMWPE) in the presence of vitamin E

Powder samples of UHMWPE (GUR 1020) containing 0.1% by wt. vitamin E (??-tocopherol, ??-T) were irradiated at room temperature in air for doses of 30-kGy, 65-kGy or 100-kGy (⁶⁰Co). After irradiation, they were stored at ?78.5°C (dry ice temperature) for one year and then opened to air at room temperature. Following the decay of the primary alkyl and allyl radicals (at room temperature in air), growth of the carbon-centered polyenyl R1 (?^·CH?CH=CH?, m ?? 3), and the oxygen-centered dior tri-enyl R2 (?^·OCH?CH=CH? _m , m ?? 3) residual radicals were measured for eight weeks. An X-band electron spin resonance (ESR) spectrometer was used for radical measurements. The initial relative radical concentrations (R2/R1) were found to be 10.13, 4.6 and 3.7 for the 65-kGy, 30-kGy and 100-kGy samples, respectively. R1 and R2 were both found to grow significantly in the 65-kGy samples while they grew only slightly in the 30-kGy and 100-kGy samples. In 65-kGy sample, R1 grew faster than R2 and the relative concentration R2/R1 was reduced from 10.13 to 2.9 for the 65-kGy sample while that for the 30-kGy and 100-kGy samples reduced only slightly, from 4.6 to 3.5 and 3.7 to 3.2, respectively. The behavior of the residual radicals can be explained by Raman spectroscopic data which suggest that the 65-kGy samples had a higher percentage of amorphous regions when compared to the 30-kGy or 100-kGy (21.7% compared to 15.7% or 17.9%) and also suggest a lower percentage of inter-phase regions (16.4% compared to 25.6% or 17.5%) and a lower level of structural disorder (0.26% compared to 0.44% or 0.27%).     

Evaluation of the antioxidant activity by flow injection analysis method with electrochemically generated ABTS radical cation

A Trolox equivalent antioxidant capacity (TEAC) decolourisation assay was adapted to a flow injection analysis (FIA) system and a simple and rapid method for antioxidant activity evaluation was developed. To avoid the time consuming step of 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid)(ABTS) radical cation preparation by chemical oxidation of ABTS, as in the original TAEC assay, and hence, to shorten the analysis time, the ABTS radical cation was generated on-line by electrochemical oxidation of ABTS in the flow-through electrolysis cell forming a part of the FIA system. The proposed method was optimised with respect to a flow rate, injection volume and ABTS radical cation/carrier ratio. Under the optimised conditions linear calibration graphs for Trolox were obtained over the range 10-100 microM, with a limit of detection 1.6 microM. Good reproducibility (relative standard deviation 1.95%) and sample throughput (32 samples per hour) were achieved. The developed method was applied to the evaluation of the antioxidant activity of pure compounds and samples of some common beverages. In both cases a good correlation between the results obtained by the proposed method and TEAC values evaluated by the classic TAEC decolourisation assay was obtained (r(2)= 0.996 for pure compounds and r(2)= 0.957 for beverage samples).     

Evaluation of the antioxidant properties of spices by cyclic voltammetry

The individual antioxidants of spices (gallic and rosmarinic acids, capsaicin, thymol, and eugenol) are irreversibly oxidized at 0.88–1.25 V at a glassy carbon electrode in 0.1 M LiClO₄ solution in ethanol. Corresponding electrode reactions are proposed. A linear dependence of the oxidation step area on the concentration is observed for all the analytes. The detection limits and the lower limits of quantification vary from 0.57–12 and 1.8–40 μM, respectively. Distinct steps and peaks of oxidation are observed on cyclic voltammograms of the methanolic extracts of spices; the potentials and areas of these peaks depend on the type of spice. The contribution of individual antioxidants to integral responses of spice extracts is evaluated. A method is developed for the voltammetric evaluation of the antioxidant capacity (AOC) of spices based on the oxidation of their antioxidants. The total area of the oxidation steps was selected as a parameter characterizing the antioxidant properties. The AOC of spices was expressed as a weight of gallic acid in milligrams per 1 g of a dry spice. Seventeen different spices were tested. The AOC decreases in the series of clove > juniper berries > nutmeg > cinnamon > rosemary > anise ≥ oregano > black pepper ≥ ginger ≥ basil > turmeric > red pepper ≈ bay leaf ≥ coriander ≈ red sweet pepper > cumin > caraway. A correlation between the AOC obtained by voltammetry and the total AOC, ferric reducing power, antiradical activity, and total content of phenolic compounds and these parameters with each other is found; the correlation coefficients vary in the range 0.8886–0.9615.     

Investigation of antioxidant and catalytic properties of some biologically active substances by voltammetry

Antioxidants play a major role in protecting biological systems against many incurable diseases. The biological activity of 12 plant aqueous-alcohol extracts, some standard antioxidants (vitamin C, glucose, resorcinol, and catechol), Na(2)SO(3), humic acids, phthalocyanines, and chlorophyll have been investigated in this work together with evaluation of their influence on the kinetics of the oxygen electroreduction. Finally the use of these substances for prophylactic purposes has been recommended.     

Two chiral cadmium carboxylate framework isomers generated by spontaneous resolution: synthesis,structures and properties

Two three-dimensional (3-D) chiral coordination polymers, [Cd(NDC)(DMF)]_n (1_L and 1_D: H₂NDC = 1,4-naphthalenedicarboxylic acid and DMF = N,N′-dimethylformamide), have been synthesized by introducing the rigid achiral dicarboxylic acid ligand under solvo-thermal conditions, without chiral template or additives. Both chiral Cd-CPs were characterized by single crystal X-ray crystallography, and structural analysis indicates that 1_L and 1_D are enantiomers based on the zigzag [Cd(COO)₂(DMF)]_n rod secondary building units, featuring the left- or right-hand 2₁ Cd-O-C-O-Cd helix chains and left- or right-hand 4₁ screw [Cd(NDC)]_n columns, respectively. The FT-IR, TGA, powder X-ray diffraction and solid-state luminescence of 1 have been investigated. It is intriguing that the evidence from the circular dichroism spectroscopies confirms enantiomeric excess in the whole spontaneous resolution crystallization.     

Improvements in compressive properties of high modulus fibers by crosslinking

A facile method was developed for crosslinking stiff chain polymer fibers such as Kevlar® and polybenzobisthiazoles (PBZT). The method is based on thermolysis of active aryl halides contained in the polymer unit and coupling of the free radicals formed. The method worked well for the PBZT polymers and improvements in fiber single filament recoil stress and shear modulus were demonstrated. In the case of the polyamides chain cleavage apparently accompanied the crosslinking, limiting improvement in the recoil stress test. The mode of degradation appeared to be rearrangement of the amide linkage to isocyanate.     

Identification by LC-ESI-MS of flavonoids responsible for the antioxidant properties of Mallotus species from Vietnam

Several Mallotus species (Euphorbiaceae) are used in Vietnam as edible plants or as traditional medicines for different indications, some related to the treatment of inflammatory diseases. This study investigated the antioxidant activities of 33 samples from 17 Vietnamese Mallotus species. We also evaluated potential cytotoxic activity against human cervix carcinoma HeLa and human lung fibroblast WI-38 cells. Our aim is to develop safe dietary supplements with a protective effect against various diseases caused by tissue damage and the acceleration of the aging process linked to reactive oxygen species. These tests allowed the identification of non-cytotoxic plant species exhibiting significant antiradical properties. These antioxidant properties may be explained by their polyphenol composition. The antioxidant activity of the most active Mallotus species was further analyzed with and without tannins removal. We also identified by LC-ESI-MS some flavonoids responsible for a part of this activity.     

Perturbation of phospholipid bilayer properties by ethanol at a high concentration

Atomistic molecular dynamics (MD) simulations have been carried out at 30 degrees C on a fully hydrated liquid crystalline lamellar phase of dimyrystoylphosphatidylcholine (DMPC) lipid bilayer with embedded ethanol molecules at 1:1 composition, as well as on the pure bilayer phase. The ethanol molecules are found to exhibit a preference to occupy regions near the upper part of the lipid acyl chains and the phosphocholine headgroups. The calculations revealed that the phosphocholine headgroup dipoles (P- --> N+) of the lipids prefer to orient more toward the aqueous layer in the presence of ethanol. It is noticed that the ethanol molecules modify the dynamic properties of both lipids as well as the water molecules in the hydration layer of the lipid headgroups. Both the in-plane "rattling" and out-of-plane "protrusion" motions of the lipids have been found to increase in the presence of ethanol. Most importantly, it is observed that the water molecules within the hydration layer of the lipid headgroups exhibit faster translational and rotational motions in the presence of ethanol. This arises due to faster dynamics of hydrogen bonds between lipid headgroups and water in the presence of ethanol.     

A study of dose verification and comparison for complex irradiation field with high dose rate radiation by using a 3D N-isopropylacrylamide gel dosimeter

Journal of Radioanalytical and Nuclear Chemistry - This study aimed to investigate dosimeter characteristics by using a photon beam with and without the flattening filter of intensity-modulated...     

Photochromic properties of [2.2]paracyclophane-bridged imidazole dimer with increased photosensitivity by introducing pyrenyl moiety

The photochromic [2.2]paracyclophane-bridged imidazole dimers show instantaneous coloration upon exposure to UV light and rapid fading in the dark. A new [2.2]paracyclophane-bridged imidazole dimer, pseudogem-PPI-DPI[2.2]PC, with high photosensitivity to UVA radiation was developed. To enhance the photosensitivity, we introduced pyrenyl moieties to the [2.2]paracyclophane-bridged imidazole dimer. The localized π-π* transition of pyrenyl moieties appears in the UVA radiation region by introducing a pyrenyl moietiy on the 4-position of the imidazole rings. The expansion of the π-electron system also affects the absorption spectrum of the colored species. The broad absorption band of the colored species covers the whole range of visible light region and its absorbance is approximately equal throughout the visible light region. Thus, pseudogem-PPI-DPI[2.2]PC shows the photochromic reaction coloring black upon light irradiation and successive fast thermal bleaching following the monoexponential kinetics with a time constant of 12 ms at room temperature.     

Ab initio quantum chemistry studies on the coding properties of cytosine derivatives generated by hydroxyl radical in aerobic conditions

The coding properties of four free radicals derived cytosine modifications were characterised by ab initio quantum chemistry method. The dimers geometry was optimised without any restrictions. The analysis was focused on the pairs consisting of a standard DNA base and one of the following cytosine derivatives: 5,6-dihydroxycytosine (1); 5,6-dihydroxyuracil (2); uracil glycol (3); and isodialuric acid (4). The presented data allow to conclude that all studied derivatives are able to form the most stable pairs with guanine. However, other pairs are also possible. In non-polar conditions the 5,6-dihydroxycytosine (1) pair with cytosine in addition to a normal pairing with guanine. This may stand for CG transversion. The significant impact of the environment polarity on the dimers stabilisation energy was observed. The potential mispairing is enriched in the polar conditions The 5,6-dihydroxyuracil (2) and isodialuric acid (4) may form stable pairs also with adenine. This may lead to CT transition. The mispairing of uracil glycol (3) was found as insignificant.     

Study of antioxidant properties of a water-soluble Vitamin E derivative-tocopherol monoglucoside (TMG) by differential pulse voltammetry

Study of antioxidant properties of tocopherol monoglucoside (TMG), a water-soluble Vitamin E derivative, by differential pulse voltammetry has been carried out in this work. The pH influence on the antioxidant properties of TMG has been also investigated. It was observed that the antioxidant activity of TMG is greater at 6.90<pH<9.18. The reactions between the TMG and reactive oxygen species have been considered. Antioxidant activity of some standard antioxidants including Vitamin E was given for comparison. The results indicate that the TMG is an effective antioxidant in neutral solutions. The oxidation potential for TMG at pH 7.31 has been found (E=0.55±0.03 V versus Ag|AgCl|KCl_sat electrode). Finally the use of TMG for protection against oxidative stress has been recommended.