Electrochemically initiated intramolecular cyclization of 2-nitro-2′-isothiocyanatobiphenyl

2-Nitro-2′-isothiocyanatobiphenyl was prepared as a new substance, suitable for the investigation of an electrochemically initiated intramolecular cyclization. If it is reduced at a mercury cathode in acidic media an acid catalysed intramolecular follow-up reaction occurs which leads to the formation of 6-mercaptodibenzo (d, f)-(1,3)-diazepin-5-oxide. The rate of the follow-up reaction decreases in neutral or alkaline media and the reduction of the isothiocyanato group also takes place. The main product is here 5,6-dihydrobenzo(c)cinnoline.     

Metabolism and biochemical/physiological roles of chondroitin sulfates: analysis of endogenous and supplemental chondroitin sulfates in blood circulation

Chondroitin sulfate (CS) is a linear heteropolysaccharide consisting of repeating disaccharide units of glucuronic acid and galactosamine, which is commonly sulfated at C-4 and/or C-6 of galactosamine. The administration of CS as a supplement or a drug for the treatment of osteoarthrosis, the prevention of subsequent coronary events, treatment of psoriasis and ophthalmic diseases has been suggested. Much debate on the metabolism of CS and therefore the effectiveness of these treatments, especially after oral administration, has arisen due to the macromolecular nature of CS. Difficulties in analysing CS in blood due to the low endogenous concentrations and the covalent and anionic complexes with proteins have hampered the resolution of these issues. In this review, the information on the pharmacokinetics of CS obtained from studies in experimental animals and in humans is presented. Emphasis has been given to the analytical methods used for the determination of glycosaminoglycans, intact CS and CS-derived disaccharides in blood serum and plasma.     

The state-dependent <Emphasis Type="Italic">M</Emphasis> / <Emphasis Type="Italic">G</Emphasis> / 1 queue with orbit

We consider a state-dependent single-server queue with orbit. This is a versatile model for the study of service systems, where the server needs a non-negligible time to retrieve waiting customers every time he completes a service. This situation arises typically when the customers are not physically present at a system, but they have a remote access to it, as in a call center station, a communication node, etc. We introduce a probabilistic approach for the performance evaluation of this queueing system, that we refer to as the queueing and Markov chain decomposition approach. Moreover, we discuss the applicability of this approach for the performance evaluation of other non-Markovian service systems with state dependencies.     

Assembly of quantum dots on peptide nanostructures and their spectroscopic properties

We present a chemical process for the decoration of self-assembled two-dimensional peptide fibrils with two different sizes of CdSe@ZnS core–shell quantum dots (Qdots) capped with trioctylphosphine oxide molecules. The attachment of the semiconducting nanoparticles to the fibrils is directed via disulfide bond between the quantum dot and cysteine aminoacids that are deliberately impeded in the peptide structures. A significant red shift in the emission spectra of the quantum dots is observed and attributed to the synergistic interaction between adjacent nanoparticles arranged on peptide film templates extending over hundreds of nanometers.     

Determination of diphenylamine in contaminated air of agricultural buildings using active sampling on solid sorbents

This paper reports the results of a study carried out with solid sorbents in order to establish the optimum procedure for sampling and determination of diphenylamine (DPA), the most widely used post-harvest chemical in apples, in the indoor air of apple storage buildings. Different sorbents (Amberlite XAD-2, Amberlite XAD-4, Supelpak 2, Florisil, and the octadecyl silica bonded sorbent, C-18) were evaluated for their capacity to efficiently retain DPA under different air sampling and storage conditions, whereas a desorption study of all sorbents tested was also performed to optimise a simple extraction procedure using low volumes of organic solvents. In general all sorbents produced acceptable results for DPA air sampling whereas DPA was recovered easily by the use of low volumes of both ethyl acetate and acetone from all sorbents studied thus making DPA a suitable analyte to be used in methods of indoor air analysis for multi-organic pollutants. However, the best results (analytical features, recovery results, and stability results during storage) were obtained by the use of Supelpak 2 as a sorbent for DPA active sampling. Limits of Quantification (LOQs) for the GC-NPD system ranged from 1.0 to 2.0?µg?m^?3 for 120 and 60?L air sampled, respectively. The developed air sampling procedure and analytical methodology was applied with success in the field to measure DPA residues in indoor air of two apple storage plants in Greece and results were further used to calculate the occupational inhalation exposure to DPA and consequently risk characterisation. Since DPA was detected in indoor air (at concentrations ranged from 1.6 to 580?µg?m^?3), there is no zero occupational risk for workers. However, the inhalation exposure of workers to DPA estimated in this study is far below the Acceptable Operator Exposure Level recently reviewed by the European Union and far below the critical exposure level for haematotoxicity systemic effect observed in carcinogenicity studies in rats for long-term inhalation exposure to DPA.     

In Silico Investigation of the Biological Implications of Complex DNA Damage with Emphasis in Cancer Radiotherapy through a Systems Biology Approach

Different types of DNA lesions forming in close vicinity, create clusters of damaged sites termed as “clustered/complex DNA damage” and they are considered to be a major challenge for DNA repair mechanisms resulting in significant repair delays and induction of genomic instability. Upon detection of DNA damage, the corresponding DNA damage response and repair (DDR/R) mechanisms are activated. The inability of cells to process clustered DNA lesions efficiently has a great impact on the normal function and survival of cells. If complex lesions are left unrepaired or misrepaired, they can lead to mutations and if persistent, they may lead to apoptotic cell death. In this in silico study, and through rigorous data mining, we have identified human genes that are activated upon complex DNA damage induction like in the case of ionizing radiation (IR) and beyond the standard DNA repair pathways, and are also involved in cancer pathways, by employing stringent bioinformatics and systems biology methodologies. Given that IR can cause repair resistant lesions within a short DNA segment (a few nm), thereby augmenting the hazardous and toxic effects of radiation, we also investigated the possible implication of the most biologically important of those genes in comorbid non-neoplastic diseases through network integration, as well as their potential for predicting survival in cancer patients.     

Corrole and Porphyrin Amino Acid Conjugates: Synthesis and Physicochemical Properties

A series of conjugates of amino acids with porphyrins and corroles was synthesized. Their self‐assembling ability under defined conditions was investigated by scanning electron microscopy. The morphology and photophysical properties of these molecules were studied by absorption and fluorescence spectroscopy in solid, liquid, and self‐assembled forms. We observed that both corrole and porphyrin conjugated with the l ‐phenylalanine–l ‐phenylalanine peptide to form spherical nanostructures with bathochromic shifts in the emission spectra, indicating the formation of aggregates. These aggregates are characterized by the impressive absorption of light over nearly the whole visible range. The broadening of all bands was particularly strong in the case of corroles. The fluorescence lifetimes of self‐assembled species were longer as compared to the solid‐state form.