On-line identification of diastereomeric dibenzo[a,l]pyrene diol epoxide-derived deoxyadenosine adducts by capillary electrophoresis-fluorescence line-narrowing and non-line narrowing spectroscopy

On the impact of the molecule structure in chemical carcinogenesis

Cancer is as a highly complex and multifactorial disease responsible for the death of hundreds of thousands of people in the western countries every year. Since cancer is clonal and due to changes at the level of the genetic material, viruses, chemical mutagens and other exogenous factors such as short-waved electromagnetic radiation that alter the structure of DNA are among the principal causes. The focus of this present review lies on the influence of the molecular structure of two well-investigated chemical carcinogens from the group of polycyclic aromatic hydrocarbons (PAHs), benzo[a]pyrene (BP) and dibenzo[a,l]pyrene (DBP). Although there is only one additional benzo ring present in the latter compound, DBP exerts much stronger genotoxic and carcinogenic effects in certain tumor models as compared to BP. Actually, DBP has been identified as the most potent tumorigen among all carcinogenic PAHs tested to date. The genotoxic effects of both compounds investigated in mammalian cells in culture or in animal models are described. Comparison of enzymatic activation, DNA binding levels of reactive diol-epoxide metabolites, efficiency of DNA adduct repair and mutagenicity provides some clues on why this compound is about 100-fold more potent in inducing tumors than BP. The data published during the past 20 years support and strengthen the idea that compound-inherent physicochemical parameters, along with inefficient repair of certain kinds of DNA lesions formed upon metabolic activation, can be considered as strong determinants for high carcinogenic potency of a chemical.

New insights in the formation of deoxynucleoside adducts with the heterocyclic aromatic amines PhIP and IQ by means of ion trap MSn and accurate mass measurement of fragment ions

The formation of adducts by reaction of active metabolites of two heterocyclic aromatic amines (NHOH-PhIP and NHOH-IQ) at nucleophilic sites of deoxynucleosides has been studied by LC-MS(n) analyses of the obtained reaction mixtures. Sequential MS(3) experiments were carried out on an ion trap mass spectrometer to gain extensive structural information on each adduct detected in the first MS step. Attribution of ions was supported by accurate mass measurements performed on an Orbitrap mass analyzer. Particular attention was given to ions diagnostic of the linking between the heterocyclic aromatic amine (HAA) and the deoxynucleoside. By this way, the structures of five adducts have been characterized in this study, among which two are new compounds: dG-N7-IQ and dA-N(6)-IQ. No depurinating adduct was found in the reactions investigated therein. As expected, the C8 and N(2) atoms of dG were found as the most reactive sites of deoxynucleosides, resulting in the formation of two different adducts with IQ and one adduct with PhIP. An unusual non-depurinating dG-N7-IQ adduct has been characterized and a mechanism is proposed for its formation on the basis of the reactivity of arylamines. A dA-N(6)-IQ adduct has been identified for the first time in this work, showing that HAAs can generate DNA adducts with bases other than dG.

Solid-liquid extraction fluorescence line narrowing spectroscopy of fluoroquinolones in aqueous samples

We present a simple, selective, and sensitive method for the analysis of fluoroquinolones in water samples without previous separation. Octadecyl silica membranes are used with the dual purpose of sample preconcentration and solid substrate for fluorescence line narrowing spectroscopy. Measurements at liquid helium temperature (4.2 K) are easily made with the aid of a cryogenic fiber-optic probe. The entire procedure takes less than 15 minutes per sample and it consumes only 100 microL of organic solvent. Unambiguous fluoroquinolone determination is accomplished via wavelength-time matrices, which provide simultaneous information on spectral peak purity and fluorescence lifetime. We show that 10 mL of water sample are enough to detect analyte concentrations at parts-per-billion levels. The potential of this approach for the analysis of real world samples is demonstrated with the analysis of a synthetic mixture of seven fluoroquinolones spiked in a heavily contaminated water sample.

Ultra-low-temperature non-aqueous capillary electrophoretic separation--77 K fluorescence spectroscopic detection for the on-line identification of photo-converted analytes of trans-resveratrol

We demonstrate here, for the first time, that non-aqueous capillary electrophoresis (NACE) can be interfaced with any ultra-low-temperature (ULT) separation method and 77 K fluorescence spectroscopy (FS). This novel ULT-NACE-FS system consists of a modular CE system, a dry ice bath, and instrumentation for 77 K fluorescence detection. The ULT-NACE method serves to separate structurally similar molecules by a combination of a low electrophoresis current and a high voltage at approximately -70 degrees C. When the ULT-NACE-separated analytes move into the quartz Dewar flask and traverse into the capillary detection window, liquid nitrogen was added, thus freezing the separating analyte zones, allowing the collection of 77 K fluorescence spectra for on-line spectral fingerprint identification. The first application of the ULT-NACE-FS system is described for the analysis of photo-converted analytes of trans-resveratrol; prospects and future applications of ULT-NACE-FS are also briefly addressed.

Recent advances in capillary electrophoresis and capillary electrochromatography of pollutants

An overview of major developments in capillary electrophoresis and capillary electrochromatography systems in the environmental field is presented, covering relevant publications between the second half of 1999 and early 2001. Contributions are reviewed in relation to developments in detection, sample preparation/preconcentration, precision and applications. Many interesting examples are shown and the influence of important parameters on the performance of developed methods is discussed.

Recent advances in pharmacokinetic applications of capillary electrophoresis

This article reviews recent capillary electrophoresis (CE)-based assays which were published for pharmacokinetic studies. Both the advantages and disadvantages of these CE-based assays are discussed based on their feasibility and the significance towards the better understanding of pharmacokinetics. In addition, as a future outlook, novel assays such as immunoaffinity CE and chip-based CE for analyzing drugs in biological fluids are summarized in view of their potential for pharmacokinetic applications.

On-line identification of 3,4-methylenedioxymethamphetamine in human urine by non-aqueous capillary electrophoresis-fluorescence spectroscopy at 77 K

The analytical profiles for 3,4-methylenedioxymethamphetamine (3,4-MDMA) and related amphetamines in urine samples are described for non-aqueous capillary electrophoresis-fluorescence spectroscopy. 3,4-MDMA was detected and identified on-line, using a cryogenic molecular fluorescence technique at 77 K. Under optimized conditions, baseline separation of the selected compounds was achieved in less than 12 min. Precision was evaluated by measuring the repeatability and intermediate precision of the migration times and corrected peak areas. The non-aqueous CE separation conditions and the spectral characteristics of 3,4-MDMA with respect to solvent and temperature effects are also discussed.

On-line identification of trans- and cis-resveratrol by nonaqueous capillary electrophoresis/fluorescence spectroscopy at 77 K

This work presents a novel method for the accurate determining trans- and cis-resveratrol (3,5,4'-trihydroxystilbene) by nonaqueous capillary electrophoresis/fluorescence spectroscopy at 77 K. The proposed method permits not only the separation of resveratrol isomers, but also ensures that on-line spectra are readily distinguishable and unambiguously assigned. The experimental results also indicate that the effect of nonaqueous capillary electrophoresis buffer and low-temperature technique increase the detection limit by more than 150-fold.

High-performance liquid chromatography interfaced with fluorescence line-narrowing spectroscopy for on-line analysis

We have demonstrated, for the first time, that high-performance liquid chromatography (HPLC) can be interfaced with fluorescence line-narrowing spectroscopy (FLNS) for on-line identification and characterization of analytes. Interfacing centered primarily on the design and construction of a novel liquid helium cryostat that accommodates variable-sized quartz tubes/capillaries suitable for HPLC as well as capillary electrophoresis/electrochromatography. In addition to the high spectral resolution afforded by FLNS, analyzing the separated components at 4.2 K minimizes photodegradation from the excitation source and provides indefinite detection times for signal averaging. The proof-of-principle for the HPLC-FLNS system is first demonstrated with a mixture of four structurally similar polycyclic aromatic hydrocarbons and then applied to the analysis of DNA adducts from mouse skin exposed to the carcinogen dibenzo[a,l]pyrene. With femtomole detection limits, HPLC-FLNS can be used for real-world analyses of complex mixtures.

Monoclonal antibody--gold biosensor chips for detection of depurinating carcinogen--DNA adducts by fluorescence line-narrowing spectroscopy

A new direct readout methodology for detection and quantitation of fluorescent carcinogen-DNA adducts is described. It combines the binding specificity of an immobilized monoclonal antibody (MAb) with high-resolution, low-temperature fluorescence spectroscopy. The MAb, which is covalently bound to a gold surface via a chemisorbed disulfide coupling agent, binds the adduct of interest in an aqueous sample. Laser-induced fluorescence under nonline narrowing (FNLN) and line-narrowing (FLN) conditions was used to detect (benzo[a]pyren-6-yl)guanine (BP-6-N7Gua) bound to immobilized MAb. At room temperature, the BP-6-N7Gua fluorescence was not detected, most likely because of quenching by the gold surface and/or efficient dynamical quenching. However, fluorescence was observed at room temperature when the surface was covered with a thin layer of glycerol, and possible reasons for the fluorescence enhancement are considered. Lowering of the temperature to 77 K led to nearly an order of magnitude increase in fluorescence intensity. Highly structured FLN spectra obtained at 4.2 K allowed for definitive adduct identification. The potential of this methodology for risk assessments of individuals exposed to polycyclic aromatic hydrocarbons is discussed.

Fluorescence line-narrowing detection in chromatography and electrophoresis

A review of the basic aspects of fluorescence line-narrowing spectroscopy (FLNS) and its coupling with thin-layer chromatography (TLC) and polyacrylamide gel electrophoresis (PAGE) for off-line high-resolution low temperature spectral characterization is discussed. This is followed by a description of the on-line interfacing of capillary electrophoresis (CE) and capillary electrochromatography (CEC) with FLN detection. CE/ CEC-FLNS instrumentation and its applications for spectral identification of closely related analytes are also presented. Future prospects of micro and capillary high performance liquid chromatography (HPLC) with on-line high-resolution low temperature spectroscopic identification are considered.

On-line identification of depurinating DNA adducts in human urine by capillary electrophoresis--fluorescence line narrowing spectroscopy

The benzo[a]pyrene (BP)-derived 7-(benzo[a]pyren-6-yl)guanine (BP-6-N7Gua) depurinating one-electron oxidation adduct was identified in the urine extracts of coal-smoke-exposed humans for the first time. Urine samples were prepared by solid-phase extraction and reversed-phase high-performance liquid chromatography. Subsequently, the BP-6-N7Gua adduct was identified on-line with capillary electrophoresis-- fluorescence line narrowing spectroscopy (CE-FLNS) at 4.2 K. The daily excretion of BP-6-N7Gua in human urine of individuals exposed to coal smoke was approximately 226 pmol per micromol of creatinine. Due to the high level of excretion we propose that BP-6-N7Gua adducts found in urine could serve as effective biomarkers for risk assessment of BP exposure. The results demonstrate that CE-FLNS allows for on-line separation and DNA adducts identification in complex fluid extracts.