CERTAIN SINGLET OXYGEN QUENCHERS AFFECT THE PHOTOREACTION BETWEEN 8-MOP and DNA

The effect of certain chemicals known as singlet oxygen quenchers on the photoreaction between 8-MOP and DNA has been studied in vitro; sodium azide, l,4-diazabicyclo-(2,2,2)-octane, p-carotene and dimethylsolfoxide (used as a solvent) appeared to be capable of reducing significantly the 8-MOP ability to induce both monoadducts and cross-links in DNA. Therefore, these chemicals seem to be not useful in studying the singlet oxygen implication in the induction of biological effects of 8-MOP sensitization.     

Direct quantitation of volatile organic compounds in packaging materials by headspace solid-phase microextraction-gas chromatography-mass spectrometry

The quantification of volatile organic compounds (VOCs) in flexible multilayer packaging materials using headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) was studied. The analytes imclude 22 compounds such as aldehydes. ketones, carboxylic acids and hydrocarbons formed by thermooxidative degradation of polyethylene during the extrusion coating process in the manufacture of the packaging, and many of them are involved in the unpleasant and undesirable odour of these materials. External standard calibration using a solution of the analytes in an appropriate solvent was the first approach studied. Aqueous solutions of the analytes provided low reproducibility and the reduction of aldehydes to alcohols under the HS-SPME conditions. Hexadecane was chosen as the solvent since its polarity is similar to that of polyethylene and its volatility is lower than that of the analytes. However, hexadecane should be added to the sample before the analysis as it modifies the absorption capacity of the fibre. A 75-microm Carboxen-poly(dimethylsiloxane) fibre was used to extract the VOCs from the headspace above the packaging in a 15-ml sealed vial at 100 degrees C after 5 min of preincubation. The influence of the extraction time on the amount extracted was studied for a standard solution of the analytes in hexadecane, together with the influence of the volume of the standard solution and the amount of the sample placed in the vial. Standard addition and multiple HS-SPME were also studied as calibration methods and the results obtained in the quantitative analysis of a packaging material were compared.     

Fourier Transform Infrared Spectroscopy and Solid Phase Extraction Applied to the Determination of Oil and Grease in Water Matrices

 The solid phase extraction as a solvent-free method for the analysis of oil and grease in waters was studied. The use of a PTFE surface as a solid phase allows the retention of the volatile fraction of oil and grease, and further analysis of carbon–hydrogen bonds using infrared spectroscopy can be done on the surface. Various oils and grease samples were tested: n-hexadecane, n-tetradecane, n-nonadecane, n-docosane, isooctane, diesel oil and gasoline. Temperatures from 25° to 90 °C and a range of heating times were checked for extraction. Precision tests showed relative standard deviation values of around 10% in several samples of the same concentration. Calibration lines of n-hexadecane showed high correlation coefficients from 0.9 to 30 mg/l. Recoveries for the various oils using different calibration lines showed values from 90 to 110%. The method described here is fast and clean, and allows reproducible measurements of oil and grease in water that do not require the use of a solvent. Received March 1, 2001; accepted August 15, 2001; published online July 15, 2002     

Speciation of the new ligand di-isopropyliminodiacetoamide with Cu(II) using computational processing and graphical methods

The importance assigned to chelating agents in diverse areas has impelled studies concerning their development as related to metal ions representing a biological concern. The synthesis of di-isopropyliminodiacetoamide (D) is presented in this work. The acidity constant obtained for D was pKa = 5.79 +/- 0.04 with the aid of program SUPERQUAD. The equilibrium constants for D with Cu(II) were obtained with the aid of program SQUAD for CuD2+ and CuD2(2)+ species giving log beta1 = 4.795 +/- 0.002 and log beta2 = 8.374 +/- 0.004, respectively.     

SO2:H2O surface complex found at the vapor/water interface

A weakly bonded SO2:H2O surface complex is found at the vapor/water interface prior to the reaction and dissolution of SO2 into the aqueous phase. The results have important implications for understanding the formation of atmospheric aerosols and understanding the atmospheric sulfur cycle.     

Generation and reactivity of 3‐carbethoxy‐5‐phenyl‐5H,7H‐thiazolo[3,4‐c]oxazol‐4‐ium‐1‐olate

3‐Carbethoxy‐5‐phenyl‐5H,7H‐thiazolo[3,4‐c]oxazol‐4‐ium‐1‐olate was generated from (2R,4R)‐N‐ethoxyoxalyl‐2‐phenylthiazolidine‐4‐carboxylic acid and its reactivity studied. This münchnone showed low reactivity as dipole although from the reaction with dimethyl acetylenedicarboxylate the corresponding (3R)‐3‐phenyl‐17H,3H‐pyrrolo[1,2‐c]thiazole‐5,6,7‐tricarboxylate could be isolated. The thermolysis of (2R,4R)‐N‐ethoxyoxalyl‐2‐phenylthiazolidine‐4‐carboxylic acid in refluxing acetic anhydride led to the synthesis of N‐(1‐ethoxycarbonyl‐2‐phenylvinyl)‐2‐phenyl‐4‐thioxo‐1,3‐thiazolidine. The structure of methyl (2R,4R)‐N‐ethoxyoxalyl‐2‐phenylthiazoliddine‐4‐carboxylate was determined by X‐ray crystallography.     

Sulle superficie di uno spazio euclideo an dimensioni aventi un campo tangente concircolare

Letx:M ²→E ⁿ be the immersion of a surfaceM ² in ann-dimensional Euclidean space. Letj and μ be the canonical isomorphism defined by the metricg ofM ² and by the canonical volume element ofM ², respectively. IfM ² carries a concircular tangent vector fieldX. then the following properties are proved:

1. The gaussian curvatureK ofM ² is identically zero.
2. X defines an infinitesimal homothety onM ².
3. The vector field (j ^?1 o μ) (X) is a Killing vector field.

Further ifX is alsoconcurrent (in the sense of K. Yano and B. Y. Chen [3]), then the immersion is degenerate (all the Killing-Lipchitz curvatures associated withx vanish).     

Antioxidative Properties and Acrylamide Content of Functional Wheat-Flour Cookies Enriched with Wild-Grown Fruits

This study aimed to evaluate the impact of widely grown fruits (wild roses, elderberries, sea buckthorns, rowans, chokeberries, and hawthorns) as a functional ingredient in wheat-flour cookie formulation on antioxidative properties with a simultaneous reduction of the carcinogen-like compound acrylamide. The organoleptic features of the cookies were assessed by a panel of consumers. The following parameters were measured: chemical composition, total polyphenols, polyphenolic profile, antioxidant activity, and acrylamide content. The overall ratings of the tested cookies with the addition of chokeberries, hawthorns, sea buckthorns, and elderberries were more than satisfactory, while wild rose and rowan cookies were the most widely accepted and best rated by the panelists. The antioxidant activity of the tested cookies was 1.1–15.22 μmol trolox·g⁻¹ dm and 2.46–26.12 μmol Fe (II)·g⁻¹ dm as measured by the ABTS and FRAP methods, respectively. All the fruit-enriched cookies had significantly higher antioxidative properties (p < 0.05) in comparison to the control cookies, but among the fruit-enriched cookies, there were differences in the quality and quantity of particular polyphenols. The acrylamide content was significantly decreased by 59% (hawthorn), 71% (rowan), 87% (wild rose), 89% (sea buckthorn), 91% (elderberry), and 94% (chokeberry) compared with the control cookies (p < 0.05). Cookies enriched with wild-grown fruits could constitute a promising novel snack food.     

Effect of Phenolic Compounds from Cymbopogon citratus (DC) Stapf. Leaves on Micellar Solubility of Cholesterol

Dyslipidemias are one of the risk factors for cardiovascular diseases, the leading cause of death and hospitalization worldwide. One way to control cholesterol levels is to control the exogenous cholesterol intake in the body. Natural polyphenolic compounds, namely theaflavins from plant extracts such as black tea, showed the ability to inhibit the formation of the micellar structure, essential for the absorption of cholesterol in the intestine. There are several methodologies to determine this effect, many of which are expensive and time-consuming. Due to these facts, the main purposes of this work were to optimize an inexpensive colorimetric method to study, in vitro, the micellar solubility of cholesterol and applied it to plant extracts. In this work, Cymbopogon citratus leaf extracts, its phenolic fractions, and flavonoids were evaluated. The non-delipidified infusion (CcI) obtained a maximum percentage of micelle destruction of 59.22% for a concentration of 50 μg/mL and the delipidified infusion (CcdI) obtained a maximum percentage of micelle destruction of 58.01% for a concentration of 200 μg/mL. In the case of the fraction of phenolic acids (CcPAs), 23.85% of maximum micellar destruction was recorded for the concentration of 100 μg/mL, while for the fraction of flavonoids (CcF), the micellar destruction was 92.74% at 1 μg/mL, and for the tannin fraction (CcT) of 99.45% at 25 μg/mL. Luteolin presented a percentage of micelle destruction of 94.83% in the concentration of 1 ng/mL, followed by luteolin-7-O-glucoside with 93.71% and luteo-lin-6-C-glucoside with 91.26% at the concentrations of 25 ng/mL and 50 ng/mL, respectively. These results suggest the capability of polyphenols from Cymbopogon citratus to prevent the cholesterol absorption in the gut by micellar destruction, and its contribution for cholesterol-lowering activity.     

Methods for Elemental Analysis of Size-Resolved PM Samples Collected on Aluminium Foils: Results of an Intercomparison Exercise

Aluminium is the most common substrate in studies using impactors for the measurement of the number or the weight of size-segregated atmospheric particulate matter (PM), as its characteristics perfectly fit impactor requirements. However, its use is not recommended by manufacturers when one of the purposes of the study is the determination of the metal content in the sample. The aim of this work was to develop an efficient analytical procedure for the removal and acid digestion of PM samples collected on aluminium foils by a cascade impactor to perform the determination of metals. The possibility of performing the trace metal analysis of PM samples collected using aluminium foils is of great importance, as it allows the determination of an accurate size distribution and the elemental composition of the PM collected on each impactor stage. Two procedures were optimised by using different digestion and analysis techniques. Both procedures were then applied to the two halves of several Dekati low-pressure impactor (DLPI) samples, and the results were critically compared. The two procedures proved to be effective in the determination of extremely low concentrations of a large suite of analytes in different size fractions of PM emitted by a brake system.