Tiaprofenic acid-photosensitized damage to nucleic acids: a mechanistic study using complementary in vitro approaches

In order to determine whether or not tiaprofenic acid (TPA) could cause cellular DNA damage, human fibroblasts were irradiated in the presence of the drug and subsequently examined by means of the comet assay. This led to the observation that TPA actually sensitizes cellular DNA to the subsequent irradiation. When TPA was irradiated in the presence of supercoiled plasmid DNA, it produced large amounts of single-strand breaks (SSB); this is consistent with the effects observed on cellular genomic DNA by the comet assay. More importantly, low concentrations of TPA, unable to produce direct SSB, caused photo-oxidative damage to DNA as revealed by the use of excision-repair enzymes. The fact that TPA-irradiated DNA was a substrate of formamidopyrimidine glycosylase as well as endonuclease III revealed that both purine and pyrimidine bases were oxidized. This was further supported by the TPA-photosensitized oxidation of 2'-deoxyguanosine which led to a product mixture characteristic of mixed type-I/II mechanisms. Thymidine was less reactive under similar conditions, but it also decomposed to give a typical type-I product pattern. Accordingly, the TPA triplet was quenched by the two nucleosides with clearly different rate constants (10(8) vs 10(7) M-1 s-1, respectively). As cellular RNA also contains oxidizable bases, it could be the target of similar processes, thus interfering with the biosynthesis of proteins by the cells. Extraction of total RNA from TPA-irradiated human fibroblasts, followed by gel electrophoresis and PCR analysis, confirmed this hypothesis. Finally, photosensitization experiments with Saccharomyces cerevisiae showed that, in spite of an efficient drug-yeast interaction leading to cytotoxicity, neither intergenic recombination nor gene conversion took place. Thus, while TPA-photosensitized damage to nucleic acids can result in genotoxicity, the risk of mutagenicity does not appear to be significant.     

Mesomorphism of a tetrahedral zinc complex

Thermotropic smectic phases have been observed for the first time in a zinc coordination complex with tetrahedral geometry; this complex, which contains the pyrazole dimer bis[3,5-bis(p-decyloxyphenyl)pyrazolyl]ethane as the ligand, exhibits fluorescence.     

Gas chromatographic-mass spectrometric characterization of all acyclic C5-C7 alkenes from fluid catalytic cracked gasoline using polydimethylsiloxane and squalane stationary phases

Published retention indices of acyclic alkenes C5-C7 on squalane and polydimethylsiloxane as stationary phases were investigated, and reliable retention indices of alkenes from various sources were converted to separation systems used in a laboratory. Retention indices measured on available authentic commercial alkenes and on alkenic fraction of gasoline, published retention indices as well as means of GC-MS were used for verification of calculated retention indices. Retention of some gas chromatographic unseparated isomer pairs was obtained by mass spectrometric deconvolution using a specific single-ion monitoring. On the basis of these retention data, C5-C7 alkenes were identified and analyzed in the gasoline from fluid catalytic cracking. In the gasoline all 59 acyclic C5-C7 isomeric alkenes were determined at significantly different concentration levels.     

Electrochemical methods for monitoring of environmental carcinogens

The use of modern electroanalytical techniques, namely differential pulse polarography, differential pulse voltammetry on hanging mercury drop electrode or carbon paste electrode, adsorptive stripping voltammetry and high performance liquid chromatography with electrochemical detection for the determination of trace amounts of carcinogenic N-nitroso compounds, azo compounds, heterocyclic compounds, nitrated polycyclic aromatic hydrocarbons and aromatic and heterocyclic amines is discussed. Scope and limitations of these methods are described and some practical applications based on their combination with liquid-liquid or solid phase extraction are given.     

Screening for defects in tryptophan metabolism

We introduced a two-step procedure for the detection of defects in metabolism of tryptophan: (1) HPTLC (described previously) is suitable when starting the investigation, (2) two HPLC methods with isocratic elution and spectrophotometric detection are used at the next step, when pathological findings are to be confirmed and the individual metabolites quantified. The first method enables the assessment of tryptophan, 5-hydroxyindolylacetic acid, indolylacetic acid, indolylacryloylglycine, indolylacrylic acid and its possible precursors, namely indolyllactic and indolylpropionic acids. The second procedure is intended for the monitoring of anthranilic, 3-hydroxyanthranilic, kynurenic and xanthurenic acids, kynurenine, 3-hydroxykynurenine and indoxyl-sulfate. The same pre-treated sample is used for all methods.     

Tuning first molecular hyperpolarizabilities through the use of proaromatic spacers

In this paper, we describe the second-order nonlinear optical properties of a series of 1,3-dithiole-based electron donor-acceptor systems incorporating proaromatic donor and spacer groups. Modification of the proaromaticity of the quinoid spacer gives rise to NLO-phores with mubeta values ranging from -2000 x 10(-)(48) esu to +3000 x 10(-)(48) esu. Quite surprisingly, compounds with a p-benzoquinoid spacer and a strong acceptor group show negative mubeta values, usually associated to zwitterionic ground states, and yet they are largely quinoid, as evidenced by crystallographic data and theoretical calculations. Progressive benzoannulation of the spacer and introduction of alkylsulfanyl substituents on the dithiole donor unit result in a shift to more positive mubeta values. DFT and ab initio calculations verify these empirical trends.     

Capillary isoelectric focusing with UV-induced fluorescence detection

Low-molecular-mass fluorescent compounds excitable in the near UV region with suitable acidobasic and electrophoretic properties are suggested as isoelectric point (pI) markers for isoelectric focusing (IEF) with UV photometric and UV excited fluorometric detection. The experimental set-up of capillary IEF with UV excited fluorometric detection and properties of new UV-induced fluorescent pI markers are given. The pI values of 18 new pI markers determined independently of IEF methods range from 2.1 to 10.3. The examples of separation of new pI markers together with derivatized proteins by capillary IEF with photometric or fluorometric detection are presented.     

Electroanalytical determination of d(GCGAAGC) hairpin

Hairpins (or hairpin-like structures) may play a major role in expansion events of triplet repeat expansion diseases (X syndrome, Huntington's disease, Friedreich's ataxia). The d(GCGAAGC) fragment has been found in the replication origins of phage phiX 174 and herpes simplex virus, in a promoter region of an Escherichia coli heat-shock gene, and in rRNA genes. The paper deals with the application of electrochemical methods to the determination of the DNA heptamer-d(GCGAAGC) which forms very stable hairpin structure in aqueous solutions. On mercury electrodes, this hairpin provides voltammetric reduction signals of adenine and cytosine, and oxidation signals of guanine. Both signals have been studied by cyclic voltammetry (CV), linear sweep voltammetry (LSV), and elimination voltammetry with linear scan (EVLS) in dependence on pH, accumulation time, scan rate, and loop sequences. The EVLS in combination with the adsorptive stripping was employed to the determination of the detection limit (LD) of this mini-hairpin (2 nM). Multidimensional voltammetric data were worked up by Fourier Transform (FT) and for the first coefficient a confidence ellipse was calculated in order to drop out some outlier data. The same method was used also for detection limit determinations. The values of LD obtained by two approaches were compared.     

Assessment of heavy metals leachability from metallo-organic sorbent-iron humate-with the aid of sequential extraction test

The sequential extraction test, known as a BCR procedure, was used to assess a leachability of heavy metals (Zn, Cd, Pb, Cu) from the metallo-organic sorbent—iron humate—loaded with these metals. The sequential test allowed to discriminate between various fractions of heavy metals, namely the acid-extractable fraction, the fraction bound to Fe oxides, and the fraction bound to organic matter. It was proven that the heavy metals are bound mainly to Fe oxides and organic matter, and thus they may be relatively hardly liberated into the environment. The BCR sequential extraction test exhibited a very good repeatability, when it was applied to the loaded sorbent—relative standard deviations were typically lower than 10%.     

Eu3+ coordination in an organic/inorganic hybrid matrix with methyl end-capped short polyether chains

Fourier Transform mid-infrared (FT-IR), Fourier Transform Raman (FT-Raman) and photoluminescence spectroscopies and Two-Dimensional (2D) Correlation Spectroscopic Analysis were employed to examine the anionic and cationic local environments in mono-urethanesils doped with europium triflate (Eu(CF(3)SO(3))(3)). The hybrid host framework of these materials is composed of a siliceous backbone bonded through urethane linkages to CH(3)-terminated polymer chains containing about 7 OCH(2)CH(2) units. Samples with infinity >/= n (composition) >/=5 (where n = OCH(2)CH(2)/Eu(3+)) were studied. In terms of ionic association, the level of complexity of these xerogels is very high. In all the compounds the triflate ions exist "free", weakly coordinated and forming cross-link separated ion pairs. At 20 >/= n >/= 5, in addition to all these species contact ion pairs occur. In agreement with these conclusions, photoluminescence establishes the presence of three distinct cation local sites (Eu(3+)/O=C(urethane cross-links), Eu(3+)/O-C-C(polyether chains) and weakly coordinated Eu(3+)/CF(3)SO(3)(-) ionic pairs).