On the solubility of azodicarbonamide in water/DMSO mixtures: an experimental and computational study.

This work aims at studying why azodicarbonamide (ADCA), a formally apolar compound with good hydrogen bond (HB) acceptors, is soluble only in polar aprotic solvents like dimethyl sulfoxide (DMSO) but not in water. Solubility measurements, as well as quantum mechanical and classical molecular dynamics simulations, were employed to tackle the problem. We found that in the liquid phase a polar conformer of ADCA (µ = 8.7 D), unreported to date, is favoured under the enthalpic drive provided by a highly polar solvent. At the same time, the very high hydrogen bond propensity of water with itself prevents this solvent from providing an effective hydrogen bond-mediated solvation. Solvents bearing good HB acceptors, while lacking strong HB donors, contribute to further stabilizing solute-solvent adducts through weak and fluxional HBs that involve the amide groups of ADCA. Implications for the solubility of ADCA down to µM concentrations were evaluated, also with the aid of classical simulations of solution nanodroplets.

Molecular dynamics investigation of benzoic acid in confined spaces.

Classical molecular dynamics simulations are carried out to investigate the aggregation of supercooled benzoic acid in confined spaces. Nanocavities, nanotubes and nanolayers are defined by restricting the periodicity of the simulation to zero, one or two dimensions, with boundaries set by adjustable, general, and computationally cheap van der Waals barriers. The effect of different confinement geometries is explored. It is found that the confinement impacts the liquid collective dynamics, strengthening the correlations that affect the motion of distant molecules. Overall, confinement determines up to a tenfold increase of the viscosity of the liquid and strongly slows down the rotational correlation times. Aggregation mediated by interactions with the walls and partial polarization of the liquid are observed. Additionally, transitions to high-density liquid states occur when stiffer barriers are used. In general, a reduced accessible amount of phase space fosters the struggle for a closer packing to relieve unfavorable atom-atom contacts, while maximizing the attractive ones. In benzoic acid, this implies that the hydrogen bond network is organized more efficiently in high density states.

Recreational inhalation of butane and propane in adolescents: Two forensic cases of accidental death.

The recreational use of inhalants is a fairly widespread habit among adolescents because of the ease of availability and methods of assumption. Their use is however not free of risks, both for direct toxicity on several target organs and for a mechanism of gas replacement with lack of oxygen. The first case concerns a 12-year-old boy who died suddenly after sniffing a mix of butane and propane contained in a can of air freshener. The second case concerns a 14-year-old boy who died by acute poisoning by the same mixture contained in a refill for lighters. High concentrations of the compounds were found in the tissues by analysis with gas chromatography-mass spectrometry. The compounds found in tissues and biological fluids were perfectly compatible with those contained in the containers used for the inhalation. The mechanisms of death were therefore assessed in a combination of the direct toxicity of the compound and oxygen replacement, thus highlighting the crucial help that toxicological analyses can provide in such cases.

The effects of acid and alkaline solutions on cut marks and on the structure of bone: An experimental study on porcine ribs.

Among taphonomical modifications during decomposition processes, little is known about the action of high or low pH to human tissues and bones. Moreover, acid or basic solutions are seldom used to ease decomposition and wrecking of the body. In this study a total of 60 samples of porcine bones on which two cut marks were produced before the beginning of the experiment, were put in six different solutions with different pH (1, 3, 5, 9, 12, 14) and analyzed every five days over a period of 70 days. Surveys were carried out macroscopically, with stereomicroscopy and with light microscopy on thin sections. Only the specimens exposed to extremely acid (<1) or basic (>12) pH showed evident modifications of the bone's structure, as witnessed by the analyses with stereomicroscopy as well. Many samples showed a detachment of the periosteum; cut marks became soon unrecognizable with pH 14 but still detectable in all the other samples. The information gained from the present study can be of great help in detecting the exposure of human tissues to high or low environmental pH and in understanding the effects that these solutions can exert on human bones.

How reliable are parenchymal tissues for the evaluation of carbon monoxide poisoning? A pilot study.

Dealing with burnt bodies, the forensic pathologist must first of all answer the question whether the victim was alive at the moment of the fire. This study aims at clarifying whether some human solid tissues may be reliably used for the forensic diagnosis of Co poisoning on burnt bodies providing no collectable blood during the autopsy. From 34 selected cases, both cardiac blood and parenchymal samples were collected to perform CO-oxymeter, spectrophotometry, and gas chromatography tests: blood CO estimations (blood COHb% and blood[CO]) and parenchymal[CO] values have been compared with special focus on R values. The solid tissues having the best correlations with blood CO amount turned out to be the lung (R 0.84), the liver (R 0.83), the kidney (R 0.79), and the spleen (R 0.92).

Death due to acute tetrachloroethylene intoxication in a chronic abuser.

Volatile substances are used widespread, especially among young people, as a cheap and easily accessible drug. Tetrachloroethylene is one of the solvents exerting effects on the central nervous system with experiences of disinhibition and euphoria. The case presented is that of a 27-year-old female, found dead by her father at home with cotton swabs dipped in the nostrils. She was already known for this type of abuse and previously admitted twice to the hospital for nonfatal acute poisonings. The swabs were still soaked in tetrachloroethylene. Toxicological and histological investigations demonstrated the presence of an overlap between chronic intake of the substance (with high concentrations in sites of accumulation, e.g., the adipose tissue, and contemporary tissue damage, as histologically highlighted) and acute intoxication as final cause of death, with a concentration of 158 mg/L in cardiac blood and 4915 mg/kg in the adipose tissue. No other drugs or medicines were detected in body fluids or tissues, and to our knowledge, this is the highest concentration ever detected in forensic cases. This peculiar case confirms the toxicity of this substance and focuses on the importance of complete histological and toxicological investigations in the distinction between chronic abuse and acute intoxication.

Drug analysis in blowfly larvae and in human tissues: a comparative study.

The present study investigates the correlation between concentrations of drugs in human tissues and Diptera larvae feeding on these tissues. Samples of liver were taken from 18 cases in which preliminary toxicological screening indicated the presence of drugs. Blowfly larvae (Diptera: Calliphoridae) were reared on these samples and subsequently analyzed for drug content. Toxicological analyses were carried out using ONLINE Abuscreen (Roche) and GC/MS for available body fluids (blood, urine and bile) as well as liver samples and maggots. All drugs detected in human tissues were also detected in insect specimens. Opiates, cocaine and barbiturates as well as some antidepressants (clomipramine, amitryptiline, nortryptiline, levomepromezine and tioridazine) were observed. Comparisons of drug concentrations between those in human tissues and blowfly larvae showed different patterns of distribution that may be attributed to differences in physiology. Results confirm the reliability of entomological specimens for qualitative analyses, although quantitative extrapolations are unreliable. All xenobiotics detected were in higher concentrations in human tissues than in maggots. Concentrations in post-feeding maggots were significantly lower than for feeding maggots, suggesting that the feeding state of maggots may affect toxicological analyses as they metabolize and eliminate drugs during development.