NEAR-UV INDUCTION OF SISTER CHROMATID EXCHANGES UNDER AEROBIC AND ANAEROBIC CONDITIONS

Abstract— The induction of sister chromatid exchanges (SCE) and cell sensitivity in mouse myeloma cells (66.2 subclone of MPC11) by irradiation with monochromatic near-UV (365 nm) light were studied under aerobic and anaerobic conditions. Sister chromatid exchanges were studied using the fluorescence-plus-Giemsa technique, and sensitivity was determined by the ability of irradiated and nonirradiated control cells to form colonies in soft agar. Cells were found to be 16 times more sensitive to near-UV light under aerobic exposure, producing an F₃₇ value of 7 × 10⁴ J/m² compared to the F₃₇ value of 11.5 × 10⁵ J/m² under anaerobic conditions. The induction of SCE was also 12 times more efficient for aerobic irradiation than for anaerobic irradiation. The data suggest that the SCE-inducing potential of DNA lesions differs when near-UV irradiation is performed in the presence or absence of air. In addition, the DNA lesions responsible for lethality and also those lesions leading to SCE induction may differ under the two irradiation conditions.     

Effect of solvents on the selectivity of terbutylazine imprinted polymer sorbents used in solid-phase extraction

A solid-phase extraction sample preparation method using a molecularly imprinted polymer (MIP) selective for the triazine type pesticide terbutylazine has been developed. The method involves preconcentration from large volumes of water samples on a C18 disk coupled to selective clean-up on the MIP. The method has been optimised by studying the recovery and retention of terbutylazine and some other structurally related triazine derivates as a function of the selective washing solvent used. The effect of the water content of the selective washing solvent was also investigated on the recovery of the MIP. River water samples were analysed with the coupled technique, and efficient clean-up of the samples was observed.     

DEPENDENCE ON STAGE OF GROWTH OF MAMMALIAN CELL SENSITIVITY TO NEAR-UV IRRADIATION*

Abstract The variable sensitivity of exponentially growing mouse myeloma cells (66.2 subclone of MPC11) to monochromatic near-UV (365 nm) radiation was studied by determination of the relative cloning efficiency (i.e. survival) of cells in soft agar. Maximum sensitivity of the cells to near-UV light was found during the middle and late stages of exponential growth when the survival was only one-tenth of that during the early stage of growth. In addition, the shapes of near-UV survival curves changed with the stage of the cells irradiated. These data indicate that stages of growth can substantially alter the response of mammalian cells to near-UV radiation. These data further suggest the importance of testing the response of the cells throughout the growth employed in the experimental procedure.     

Intercalation of organic dye molecules into double-stranded DNA. Part 2: the annelated quinolizinium ion as a structural motif in DNA intercalators

DNA intercalators represent an important class of compounds with a high potential as DNA-targeting drugs. In this review it is demonstrated that annelated quinolizinium derivatives such as coralyne and derivatives thereof intercalate into DNA and that this structural motif allows several variations of the substitution pattern without loss of intercalating properties. The commonly applied methods for the evaluation of the DNA association, mainly spectroscopic studies, are pointed out. In addition, studies on the biological activities of annelated quinolizinium derivatives, such as topoisomerase poisoning or cell toxicity, are highlighted.     

Synthesis of new optically active acridino-18-crown-6 ligands and studies of their potentiometric selectivity toward the enantiomers of protonated 1-phenylethylamine and metal ions

Starting from commercially available and relatively inexpensive chemicals, new enantiopure diisobutyl- and dioctyl-substituted acridino-18-crown-6 ether-type ligands [(R,R)-3] and [(R,R)-4], respectively were prepared. The two lipophilic isobutyl [(R,R)-3] and octyl [(R,R)-4] groups on the stereogenic centers of these macrocycles made it possible to use them as potentiometric sensor molecules when incorporated into plasticized PVC membrane electrodes. Ligand (R,R)-3 showed appreciable enantioselectivity toward the enantiomers of 1-phenylethylammonium chloride while macrocycle (R,R)-4 exhibited a high selectivity toward the silver ion.     

Oxidant aggregate-induced porosity in vapour-deposited polymer films and correlated impact on electrochemical properties

ABSTRACT

Persistently doped conjugated polymers are integral for energy storage, flexible electronics, and biosensors due to their unique ability to interact with both ionic and electronic currents. To maximise the performance of devices across these fields, research has focused on controlling material properties to optimise conductivities of both types of charge carriers. The challenge lies in improving ionic transport, which is typically the rate-limiting step in redox processes, without sacrificing electronic conductivity or desirable mechanical properties. Here we report on control of nanostructure in vapour deposited conducting polymer films and correlate changes in film structure with resulting electrochemical properties. Structural control is enabled by exploiting the growth of oxidant nanoaggregates during the reactive vapour deposition process. Relative to dense films, porous films exhibit faster response times in electrochemical testing. Scan rate analysis confirms a transition away from diffusion-limited charging kinetics and demonstrates the important role that porosity can play in ion transport through electroactive polymers. Advantageously, continuous polymer networks remain evident in nanostructured films, ensuring that high electronic conductivities are maintained along with high porosity. We find that such enhanced properties are retained even as polymer thickness increases ten-fold. The films reported herein may serve as robust electrodes in flexible electrochemical devices.     

In–CuInS2 nanocomposite film prepared by pulsed laser deposition using a single source precursor

An In–CuInS₂ nanocomposite film has been prepared by Pulsed Laser Deposition applying a single source precursor. X-ray powder diffraction, Raman spectroscopy and transmission electron microscopy observations evidence that the film consists of nanocrystals of elemental In and chalcopyrite type CuInS₂ with sizes of 36 and 17 nm respectively. A detailed analysis of the electrical performance of the film suggests that the nanoparticles are in Ohmic contact and that the resistivity is mainly caused by the CuInS₂ nanocrystals which are less conducting than the pure In metal. Irradiation of the film with light shows a photoconductive effect mainly with wavelengths larger than 515 nm and smaller than 850 nm.     

Induction of apoptosis by photoexcited tetracyclic compounds derivatives of benzo[b]thiophenes and pyridines

The antiproliferative activity, upon UVA irradiation, of two tetracyclic derivatives of benzo[b]thiophenes and pyridines, a benzo[b]thienopyridopyrimidone (1) and a thienocarboline (2), has been investigated in a panel of human tumor cell lines. The two compounds present a remarkable cytotoxicity after UVA irradiation (365 nm), reaching an IC50 of 0.1 microM in the leukaemia cell lines and 0.3-0.5 microM in the solid tumour cell lines. Their effect on the cell cycle was measured by flow cytometry in Jurkat cells. The compounds induce cell cycle perturbations and trigger a massive apoptosis as revealed by the externalisation of Annexin V-targeted residues at the outer plasmatic membrane. Furthermore the drugs induce, upon UVA irradiation significant variations of the mitochondrial potential (Deltapsi(mt)) measured by flow cytometry using the fluorochrome JC-1. In addition we characterized the mitochondrial production of reactive oxygen species (ROS) using the probe dihydroethidine (HE) and the oxidations of the mitochondrial phospholipid cardiolipin using the interacting probe nonyl acridine orange (NAO). Both compounds stimulate the production of ROS, and remarkably induce oxidation of cardiolipin. We have investigated the DNA-binding properties of these two compounds by means of UV-Vis spectroscopy and fluorescence. The two compounds exhibit a low affinity toward the macromolecule. The mode of binding was also investigated by means of flow linear dichroism (LD) which has revealed that the two compounds do not efficiently intercalate into DNA. Finally, the DNA-photocleavaging properties of the test compounds were studied on pBR322 plasmid DNA as a model. Only compound 1 is able to induce a significant production of single strand breaks only after digestion with the base excision repair enzyme Endo III. Altogether these data suggest that DNA is not a preferential target of these molecules and other subcellular structures may be responsible for their high phototoxic activity.     

Funzioni continue da una parte con particolare riguardo alla loro derivabilità unilaterale

Sunto Si estende alle funzioni continue da una parte un teorema fondamentale diDenjoy sui numeri derivati e se ne traggono notevoli conseguenze. Si dimostra che l'aggregato dei punti di discontinuità è numerabile, che sotto determinate condizioni può essere denso e in quest'ultima ipotesi se ne studia la struttura. Si dànno infine degli esempi di funzioni continue verso destra.     

The kinetics of charging and discharging of iridium oxide films in aqueous and non-aqueous media

Cyclic voltammetry and chronocoulometry have been used to investigate the kinetics of oxidation and reduction of electrochenucally generated Ir oxide films in H₂SO₄(aq), basic aqueous LiClO₄ solutions and LiClO₄ + acetonitrile solutions. In acidic aqueous solutions, the scan rate at which the main anodic peak potential begins to shift positively in cyclic voltammetry experiments has been used as a parameter to assess the charging and discharging kinetics of Ir oxide films grown under various conditions. In acidic and basic aqueous solutions, chronocoulometric measurements indicate that electron transport through the oxide is rate limiting for the main redox wave, whereas ion transport probably limits the charging/discharging kinetics in LiClO₄ + CH₃CN solutions. In this non-aqueous medium, it appears that ca. 35% of the oxide sites charge and discharge approximately an order of magnitude more rapidly than the remaining sites.