Dechlorane Plus and related compounds in aquatic and terrestrial biota: a review

Dechlorane Plus, dechlorane 602, dechlorane 603 and dechlorane 604 are flame retardants that have been used for a long time as a substitute for mirex, but they have not been noticed as environmental contaminants until recently (2006). Regardless of their large molecular size and very high lipophilicity (log K _OW?>?9), Dechlorane Plus and related compounds have been detected in different aquatic and terrestrial species, supporting their bioaccumulation and biomagnification. Moreover, some studies showed different behaviour of the syn-Dechlorane Plus and anti-Dechlorane Plus isomers in the environment and different biomagnification factors in biota. This review describes the different analytical approaches applied to the determination of Dechlorane Plus and related compounds. Moreover, a summary of their levels in aquatic and terrestrial biota, as well as in humans, is presented, showing also current research results on their bioaccumulation and biomagnification potential. Finally, isomer-specific bioaccumulation of Dechlorane Plus is also discussed.     

Synthesis of asymmetrically substituted 1,4,7,10-tetraazacyclododecanes for the triggered near infrared emission from lanthanide complexes

A synthetic strategy to prepare asymmetrically substituted 1,4,7,10-tetrazadodecane derivatives was developed to prepare a novel series of photoactive donor-acceptor quencher triads based on Yb and Nd complexes; a nucleoside quencher is used to regulate the extent of energy transfer between the donor and the acceptor.     

Characterization of the flow of anisotropic colloidal particles using energy-dispersive X-ray diffraction

The technique of energy-dispersive X-ray diffraction to study the orientation of microscopic crystalline particles dispersed in a liquid has been described recently. This complements previous neutron diffraction studies by permitting measurements at higher spatial resolution. Work with synchrotron radiation and high-energy X-rays has allowed studies on liquid dispersions flowing in pipes with a thickness of about 1 cm and a spatial resolution of 100 mum. Kaolinite is often found as a dispersion of monocrystalline, microscopic plates. The crystallographic layer structure is commensurate with the particle shape: the 00l direction is normal to the plane of the plates. Measurements of diffraction of the flowing liquid dispersion in a pipe oriented in various directions to the incident beam can be used to deduce the average orientation and order parameters of the particles. The competing effects of alignment with walls and in flow fields were observed. Further work has measured the orientation near a bend in a pipe.     

Detection of polymorphism in the methlyenetetrahydrofolate reductase gene by Raman spectroscopy

A novel approach using micro‐Raman spectroscopy for the detection of alteration of global DNA methylation levels in human individuals with polymorphism in the methlyenetetrahydrofolate reductase (MTHFR) gene was tested. Comparison of measured Raman spectra from samples with wild type genotype to those with polymorphism (homozygous and heterozygous ) in the MTHFR gene revealed that the intensity of the ~ 2945 cm^–1 peak, representing C–H stretches in the DNA constituents and in the methyl group is sample dependent. The intensity ratios between the area of these peaks in the different samples and the peaks at 1667 cm^–1 were used to assess the extent of methylation, allowing classification of the DNA samples for the common MTHFR polymorphism, MTHFR 677 C > T. These results suggest that improvement of the identification capabilities of Raman spectroscopy for DNA methylation can contribute to disease diagnosis and to a better understanding of the physical and biomolecular processes related to epigenetic regulation of the genome. Copyright © 2012 John Wiley & Sons, Ltd.     

Signal-to-noise ratio and aberration statistics in ocular aberrometry

We define a signal-to-noise ratio (SNR) for eye aberrometry in terms of the sensor geometry, measurement noise, and population statistics. The overall estimation error is composed of three main contributions: the bias in the estimated modes, the truncation error, and the error due to the noise propagation. This last term can be easily parametrized by the proposed SNR. We compute the overall error as well as the magnitude of its three components for a typical sensor configuration, population statistics, and different SNR. We show that there are an optimum number of Zernike aberration modes to be retrieved in each case.     

Bioorthogonally Assisted Phototherapy: Recent Advances and Prospects

Photoresponsive materials offer excellent spatiotemporal control over biological processes and the emerging phototherapeutic methods are expected to have significant effects on targeted cancer therapies. Recent examples show that combination of photoactivatable approaches with bioorthogonal chemistry enhances the precision of targeted phototherapies and profound implications are foreseen particularly in the treatment of disperse/diffuse tumors. The extra level of on-target selectivity and improved spatial/temporal control considerably intensified related bioorthogonally assisted phototherapy research. The anticipated growth of further developments in the field justifies the timeliness of a brief summary of the state of the art.     

Miscibility‐property correlations in blends of glassy amorphous polymers

Blends were prepared from seven polymers in various combinations in the entire composition range. The Flory‐Huggins interaction parameter (χ₁₂) was used for the quantitative estimation of miscibility. The determination of χ₁₂ was attempted by several experimental techniques including the measurement of transparency, glass transition temperature, solvent diffusion and mechanical properties. The relatively simple methods used for the estimation of miscibility work surprisingly well. Solvent absorption can be determined easily for practically all blends, thus the method offers a quantitative measure of component interaction if the solvent is selected properly. After appropriate data reduction, the composition dependence of mechanical properties also supplies a quantitative estimate of compatibility. Although the approach presented in the paper reflects well the general correlation between miscibility and properties, it must be refined and improved in order to obtain a reliable estimate of blend performance.     

Maximum Impact of Ionic Strength on Acid-Catalyzed Reaction Rates Induced by a Zeolite Microporous Environment

The intracrystalline ionic environment in microporous zeolite can remarkably modify the excess chemical potential of adsorbed reactants and transition states, thereby influencing the catalytic turnover rates. However, a limit of the rate enhancement for aqueous-phase dehydration of alcohols appears to exist for zeolites with high ionic strength. The origin of such limitation has been hypothesized to be caused by the spatial constraints in the pores via, e.g., size exclusion effects. It is demonstrated here that the increase in turnover rate as well as the formation of a maximum and the rate drop are intrinsic consequences of the increasingly dense ionic environment in zeolite. The molecularly sized confines of zeolite create a unique ionic environment that monotonically favors the formation of alcohol-hydronium ion complexes in the micropores. The zeolite microporous environment determines the kinetics of catalytic steps and tailors the impact of ionic strength on catalytic rates.