Photoelectrochemical genosensors for the determination of nucleic acid cancer biomarkers

Liquid biopsy consists of a test or a series of tests carried out on a sample of blood to monitor circulating biomarkers, including nucleic acids. In cancer, a liquid biopsy approach can be useful not only for a rapid diagnosis, but also for therapy selection and cancer patient monitoring during treatment. However, the analytical assays need to be very sensitive (capable of detecting very small amounts of circulating analytes) as well as selective.Photoelectrochemistry is a powerful technique of developing an analytical biosensing assay, since it possesses advantages of both optical and electrochemical methods by coupling light excitation and electrochemical detection, and thus resulting in potentially very sensitive measurements due to the low background current. The aim of this review is to describe photoelectrochemical genosensors and to point out the potential of this class of genosensors in determining circulating nucleic acids as well as the challenges in the frame of a liquid biopsy approach.     

Dual column capillary gas chromatographic system for the in situ analysis of volatile organic compounds on a cometary nucleus

Two Wall Coated Open Tubular capillary columns, coated with poly(cyanopropylphenyl-dimethyl)siloxane and poly(diphenyl-dimethyl)siloxane stationary phases, have been selected for use in the COmetary SAmpling and Composition space experiment for the separation and identification of the wide range of volatile organic compounds which could be present in cometary nuclei. This article presents the main characteristics of the tandem column system for the analysis of solutes of cometary interest within the constraints of space instrumental operating conditions. The high efficiency of the columns is demonstrated and the influence of the operating conditions on their separation properties are investigated. The studied columns exhibit complementary retention pattern: their use in a dual column system makes it possible to achieve the separation and the identification of the compounds of interest. Finally, the good analytical behavior of the columns when analyzing samples which include large amounts of water, the main presumed volatile in comets, is demonstrated. The presented results thus show the suitability of the selected tandem columns system for the desired analyses, and their performance on adaptation to in-situ cometary chemical investigation.     

On the density of the splitting of 2 in cubic fields

Summary In this paper we consider all algebraic integers of degree 3 and all possible splittings of the ideal generated by 2 in cubic fields; we determine the density of the 's such that the splitting of 2 inQ() is fixed. We also obtain the density of the integers generating cubic fields of index 2.     

Enantiospecific synthesis of 3-aza-6,8-dioxa-bicyclo[3.2.1]octane carboxylic acids from erythrose

New methodology for the synthesis of enantiopure 3-aza-6,8-dioxa-bicyclo[3.2.1]octane-carboxylic acids belonging to 7-endo-BTAa sub-class of γ/δ amino acids is described. The novelty is the use of 2,3-O-isopropylidene-erythrose instead of meso-tartaric acid derivative, thus allowing us to perform an enantiospecific synthesis. Reductive amination of erythrolactol with aminoacetaldehyde diethylacetal or benzylamine, and subsequent acid cyclisation gave directly the amino alcohol scaffold. Protection of nitrogen as urethane and final alcohol oxidation afforded the Fmoc-, Boc-, and Cbz-amino acids. The new synthetic route was applied to multigram scale, thus resulting in a marked improvement of the synthesis of enantiopure 7-endo-BTG and 7-endo-BTK amino acids.     

Multifrequency EPR study and density functional g-tensor calculations of persistent organorhenium radical complexes

The dinuclear radical anion complexes [(mu-L)[Re(CO)(3)Cl](2)](*)(-), L = 2,2'-azobispyridine (abpy) and 2,2'-azobis(5-chloropyrimidine) (abcp), were investigated by EPR at 9.5, 94, 230, and 285 GHz (abpy complex) and at 9.5 and 285 GHz (abcp complex). Whereas the X-band measurements yielded only the isotropic metal hyperfine coupling of the (185,187)Re isotopes, the high-frequency EPR experiments in glassy frozen CH(2)Cl(2)/toluene solution revealed the g components. Both the a((185,187)Re) value and the g anisotropy, g(1) - g(3), are larger for the abcp complex, which contains the better pi-accepting bridging ligand. Confirmation for this comes also from IR and UV/vis spectroscopy of the new [(mu-abcp)[Re(CO)(3)Cl](2)](o/)(*)(-)(/2)(-) redox system. The g values are reproduced reasonably well by density functional calculations which confirm higher metal participation at the singly occupied MO and therefore larger contributions from the metal atoms to the g anisotropy in abcp systems compared to abpy complexes. Additional calculations for a series of systems [(mu-abcp)[M(CO)(3)X](2)](*)(-) (M = Tc or Re and X = Cl, and X = F, Cl, or Br with M = Re) provided further insight into the relationship between spin density distribution and g anisotropy.     

Application of an optimization procedure in adsorptive stripping voltammetry for the determination of trace contaminant metals in aqueous medium

A procedure for the determination of the contaminant metal In(III) by differential pulse adsorptive stripping voltammetry (DPAdSV) using ammonium pyrrolidine dithiocarbamate (APDC) as a complexing agent, has been optimized. The selection of the experimental conditions was made using experimental design methodology by means of a robust regression method which allows the elimination of anomalous points. The detection limit obtained was 1.3×10⁻⁹ mol dm⁻³. Possible interferences from concomitant metal ions were evaluated. Among all the metals analyzed, only Cd(II) was found to create an interference. This fact made impossible to carry out the determination of In(III) in the presence of Cd(II) using a univariate calibration. This problem was solved using multivariate regression techniques such as partial least squares (PLS). The procedure was successfully applied to the determination of indium in different aqueous samples.     

Synthesis of helical [2.2]paracyclophanes containing carbocyclic and heterocyclic five-membered rings

The preparation of a [2.2]indenoparacyclophane-based diene is described. Diels-Alder cycloadditions of this diene with N-methylmaleimide, N-phenylmaleimide and maleic anhydride occurred in good yields and anti-diastereoselectively only under high pressure conditions. Heterohelicenophanes were prepared by dehydrogenation of the Diels-Alder products with 10% Pd/C catalyst. A new helicenophanequinone was obtained by the reaction between the diene and 1,4-naphthoquinone.