A method for measuring the bioaccessibility of polycyclic aromatic hydrocarbons in cell culture media.

Airborne polycyclic aromatic hydrocarbons (PAHs) and their derivatives are of particular concern for population health due to their abundance and toxicity via inhalation. Lung toxicity testing includes exposing lung epithelial cell lines to PAHs in a culture medium containing inorganic species, lipids, proteins, and other biochemicals where the cell response is influenced among others by the toxic chemical accessibility in the medium. While inhalation bioaccessibility of PAHs and other toxicants was previously studied in surrogate lung fluids, studies measuring bioaccessibility in cell culture media are rare.

Profiling quinones in ambient air samples collected from the Athabasca region (Canada).

This paper presents new findings on polycyclic aromatic hydrocarbon oxidation products-quinones that were collected in ambient air samples in the proximity of oil sands exploration. Quinones were characterized for their diurnal concentration variability, phase partitioning, and molecular size distribution. Gas-phase (GP) and particle-phase (PM) ambient air samples were collected separately in the summer; a lower quinone content was observed in the PM samples from continuous 24-h sampling than from combined 12-h sampling (day and night).

Characterization of the ambient air content of parent polycyclic aromatic hydrocarbons in the Fort McKay region (Canada).

This study presents the characterization of the gas-particle partition and size distribution of seven parent polycyclic aromatic hydrocarbons (PAHs) in ambient air samples collected in the proximity of oil sands exploration and compares their time-integrated concentration levels with nineteen analogous oxidation products - quinones. Gas-phase (GP) and particle-phase (PM) ambient air aerosol samples that were collected separately in summer for either 24 h or 12 h (day and night) revealed a higher PAH partition in the GP than in the PM, with the distribution over tenfold higher for light over heavy PAHs. Diurnal/nocturnal samples demonstrated that night conditions lead to lower concentrations, linking some of the sources of these compounds with daytime activity emissions.

Mechanistic pathways of formation of acrylamide from different amino acids.

Studies on model systems of amino acids and sugars have indicated that acrylamide can be generated from asparagine or from amino acids that can produce acrylic acid either directly such as beta-alanine, aspartic acid and carnosine or indirectly such as cysteine and serine. The main pathway specifically involves asparagine and produces acrylamide directly after a sugar-assisted decarboxylation and 1,2-elimination steps and the second non-specific pathway involves the initial formation of acrylic acid from different sources and its subsequent interaction with ammonia to produce acrylamide. Aspartic acid, beta-alanine and carnosine were found to follow acrylic acid pathway.

The role of creatine in the generation of N-methylacrylamide: a new toxicant in cooked meat.

Investigations of different sources of acrylamide formation in model systems consisting of amino acids and sugars have indicated the presence of two pathways of acrylamide generation; the main pathway specifically involves asparagine to directly produce acrylamide after a sugar-assisted decarboxylation step, and the second, nonspecific pathway involves the initial formation of acrylic acid from different sources and its subsequent interaction with ammonia and/or amines to produce acrylamide or its N-alkylated derivatives. Aspartic acid, beta-alanine, and carnosine were found to follow the acrylic acid pathway. Labeling studies using [(13)C-4]aspartic acid have confirmed the occurrence in this amino acid of a previously proposed sugar-assisted decarboxylation mechanism identified in the asparagine/glucose model system.

Monitoring carbonyl-amine reaction between pyruvic acid and alpha-amino alcohols by FTIR spectroscopy--a possible route to Amadori products.

The carbonyl-amine reaction between pyruvic acid and alpha-amino alcohols was monitored by Fourier transform infrared spectroscopy at a temperature range between 20 and 100 degrees C and under acidic and basic conditions. To avoid interference, the reactions were conducted in the absence of solvent using liquid reactants such as methyl pyruvate, pyruvic acid, ethanolamine, and 1-amino-2,3-propanediol. Analysis of the time- and temperature-dependent spectra indicated that under basic conditions and at room temperature, the initial imine formation and its subsequent isomerization through a 1,3-prototropic shift occur very rapidly and the reaction goes to completion within 12 min.

Why asparagine needs carbohydrates to generate acrylamide.

Structural considerations dictate that asparagine alone may be converted thermally into acrylamide through decarboxylation and deamination reactions. However, the main product of the thermal decomposition of asparagine was maleimide, mainly due to the fast intramolecular cyclization reaction that prevents the formation of acrylamide. On the other hand, asparagine, in the presence of reducing sugars, was able to generate acrylamide in addition to maleimide.