In fish, metabolites of polycyclic aromatic compounds (PACs) in gall bladder bile can be used as ... more In fish, metabolites of polycyclic aromatic compounds (PACs) in gall bladder bile can be used as biomarkers for recent environmental exposure to PACs. These metabolites in the bile result from hepatic biotransformation processes whereby the lipophilic parent PACs are transformed in two steps (hydroxylation and subsequent conjugation) to more soluble forms and then passed to the gall bladder for elimination from the organism. As a biomarker of exposure, the determination of PAC metabolites in bile has several advantages over other assessment techniques. Several bile PACs are strong fluorophores and can thus be measured semi-quantitatively and very easily by means of straightforward fluorescence detection techniques. For example, fixed fluorescence detection and synchronous fluorescence scanning can be used for this purpose. These techniques are excellent for rapid screening of overall PAC exposure levels, but less suitable for the determination of individual compounds. The next level...
Fluorescence line-narrowing spectroscopy (FLNS) is a cryogenic technique that can be used to obta... more Fluorescence line-narrowing spectroscopy (FLNS) is a cryogenic technique that can be used to obtain high-resolution fluorescence spectra. The technique has mainly been used for fingerprint identification. However, this review focuses on the trend to use FLNS for probing purposes: obtaining information on interactions with the local environment or determining conformations. We briefly discuss the basics of FLNS, solute-matrix interactions and important instrumental aspects. We describe examples from various bioanalytical fields: DNA adducts of the aromatic carcinogen benzo[a]pyrene (BP); binding of BP metabolites to monoclonal antibodies or the estrogen receptor; FLNS studies of porphyrin-containing proteins; and, photosynthetic systems. As an illustration from the field of environmental chemistry, we discuss the use of luminescence line-narrowing spectroscopy-a special mode of FLNS-to study the complexation of lanthanides to humic substances.
The main objective of the EU-network is to bring together scientists with a background in analyti... more The main objective of the EU-network is to bring together scientists with a background in analytical chemistry interested in speciation method development with potential users from industry and representatives from legislative bodies. The network started on 1/10/1997 for a duration of 2 years. A series of meetings are being organised to debate all the important questions for collecting information on environmental, food and occupational health aspects of speciation and to define possible future projects. The findings and conclusions will be summarised as a series of general papers that will be published in the open literature, recapitulating the essential information gathered to date, outlining the state of the art for each topic and recommending legislative actions. A first meeting was held in Überlingen, Germany on 5-6 December 1997. The representatives from industry explained their interest in the network and the participants from the academic and national institutes gave a state-of-the-art
Conference on Lasers and Electro-Optics 2010, 2010
A variety of evanescent-wave cavity-enhanced techniques is used in studying interfacial kinetics ... more A variety of evanescent-wave cavity-enhanced techniques is used in studying interfacial kinetics as well as the performance of anti-biofouling coatings, demonstrating the potential of these techniques in label-free biosensing.
This article appeared in a journal published by Elsevier. The attached copy is furnished to the a... more This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/copyright
Deuteration effects on the vibronic structure of the emission and excitation spectra of triangula... more Deuteration effects on the vibronic structure of the emission and excitation spectra of triangular [4]phenylene (D 3h [4]phenylene) were studied using laser-excited Shpol'skii spectroscopy (LESS) in an octane matrix at 4.2 K. For correct assignment of the vibrational modes, the experimental results were compared with calculated frequencies (B3LYP/6-31G*). CH vibrations were identified by their characteristic isotopic shift in the spectra of deuterated triangular [4]phenylenes. Two CC stretching modes, at 100 cm-1 and 1176 cm-1 , suitable as probes for bond strength changes in the excited state, were identified. The isotope effect on the internal conversion rates of triangular [4]phenylene was evaluated from temperature dependent lifetime measurements. Isotope dependency and the magnitude of the internal conversion rates indicate that internal conversion in triangular [4]phenylene is most likely induced by CH vibrations. The results obtained by LESS and lifetime measurements were compared with PM3 PECI calculations of the excited state structure. The theoretical results and the relation between ground and excited state vibration energies of the 1176 cm-1 probe vibration indicate a reduction of bond alternation of the central cyclohexatriene ring in the excited state.
Vibrationally resolved fluorescence spectra of four angular [N]phenylenes were recorded with lase... more Vibrationally resolved fluorescence spectra of four angular [N]phenylenes were recorded with laser excited Shpol 'skii spectroscopy (LESS) in an n-octane matrix at 10 K. In general, the same vibrational frequencies were observed in the fluorescence excitation and emission spectra, indicating that the geometries of ground and electronically excited state are very similar. Because of intensity borrowing from the S 2 state, vibrations of two different symmetries were observed in the fluorescence excitation spectra of angular [3]phenylene and zigzag [5]phenylene. This finding allowed the location of the S 2 state for these compounds. DFT calculations (RB3LYP/6-31G*) of the ground state vibrational frequencies were made. The calculated vibrational modes were in reasonably good agreement with the experimental data. A new very low-frequency vibration of approximately 100 cm À1 was predicted and experimentally confirmed for all [N]phenylenes investigated. This vibration seems to be unique for [N]phenylenes and is attributed to an in-plane movement of the carbon backbone.
Organic contaminants [polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), polybro... more Organic contaminants [polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), polybrominated diphenylethers (PBDEs), nonylphenols], organotin compounds and trace metals (cadmium, chromium, mercury and zinc) were determined in flounder (Platichthys flesus) liver and sediment from the Amsterdam harbour (North Sea Canal) and Rotterdam harbour (Euromonding) and off the Dutch coast between the Amsterdam and Rotterdam harbour mouths in order to assess the level of contamination in these harbours and to study contamination gradients.
Tranexamic acid (TA) is a synthetic antifibrinolytic agent that is being considered as a candidat... more Tranexamic acid (TA) is a synthetic antifibrinolytic agent that is being considered as a candidate adjuvant drug for site-specific pharmaco-laser therapy of port wine stains. For drug utility studies, a high-performance liquid chromatography (HPLC)-fluorescence method was developed for the quantification of TA in blood. Platelet-poor plasma was prepared, size-separated using 3 kDa cutoff centrifuge filters, and derivatized with naphthalene-2-3-dicarboxaldehyde (NDA) and cyanide. The excess of NDA was quenched after 2 min by adding tryptophan. The derivatives were separated on a 2.1 mm C18 column using an acetate buffer/acetonitrile gradient. Excellent separation from plasma background was obtained at pH 5.5. Quantification was carried out at 440/520 nm. The limit of detection was 0.5 M and the mean ± SD recovery from whole blood was 81.7 ± 10.9%. Derivatized TA samples were stable for at least 36 h at 4 • C. The method was successfully applied to a heat-induced TA release study from thermosensitive liposomes.
With 15 flavonoids as test compounds, the analytical performance of four modes of LC-MS, multiple... more With 15 flavonoids as test compounds, the analytical performance of four modes of LC-MS, multiple MS (MS) and tandem MS operation (atmospheric pressure chemical ionization (APCI), electrospray ionization, positive and negative ionization) was compared for two mass spectrometers, a triple-quadrupole and an ion-trap instrument. Two organic modifiers, methanol and acetonitrile, and two buffers, ammonium acetate and ammonium formate, were used. In general, the use of APCI in the negative ion mode gave the best response, with the signal intensities and the mass-spectral characteristics not differing significantly between the two instruments. The best results were obtained when methanol-ammonium formate (pH 4.0) was used as LC eluent. Under optimum conditions full-scan limits of detection of 0.1-30 mg / l were achieved in the negative APCI mode. Here it needs to be emphasized that up to 2-order response differences were found both between analytes and between modes of ionization. This implies that one should be very cautious when interpreting data on the n screening of real-life samples. The main fragmentations observed in the MS spectra on the ion-trap, or the tandem MS spectra on the triple-quadrupole were generally the same. The advantage of the former approach is the added possibility to ascertain precursor→product ion relationships.
Utilizing the concept of shear-driven chromatography, we have been able to realize reversed-phase... more Utilizing the concept of shear-driven chromatography, we have been able to realize reversed-phase LC separations in flat rectangular nano-channels coated with a C8 monolayer and being as thin as 100 nm. At this scale, the separation kinetics are strongly enhanced, as is witnessed by the extremely short time (< 0.1 s) needed to separate a mixture of coumarin dyes. The observed plate numbers are still relatively small, because the experiments were conducted in ultra-short columns (< or = 1 mm) and under injection band width-limiting conditions.
The environmental impact and recovery associated with the long and uninterrupted disposal of larg... more The environmental impact and recovery associated with the long and uninterrupted disposal of large volumes of moderately contaminated dredged material from the port of Rotterdam was studied at nearby dumping sites in the North Sea. Observations were made on sediment contamination, ecotoxicity, biomarker responses and benthic community changes shortly after dumping at the 'North' site had ceased and at the start of disposal at the new dumping site 'Northwest'. During the period of dumping, very few benthic invertebrates were found at the North site. Concentrations of cadmium, mercury, polychlorinated biphenyls (PCBs), polyaromatic hydrocarbons (PAHs) and tributyltin (TBT) in the fine sediment fraction (< 63 mm) from this site were 2-3 times higher than at the reference site. In four different bioassays with marine invertebrates the sediments showed no acute toxic effects. In tissue (pyloric caeca) of resident starfish Asterias rubens, residual levels of mercury, zinc, PCBs and dioxin-like activity were never more than twice those at the reference site. Four different biomarkers (DNA integrity, cytochrome P450 content, benzo[a]pyrene hydroxylase activity and acetylcholinesterase inhibition) were used on the starfish tissues, but no significant differences were found between North and the reference site. Minor pathological effects were observed in resident dab Limanda limanda. One year after dumping had ceased at the North site, a significant increase in the species richness and abundance of benthic invertebrates and a concomitant decrease in the fine sediment fraction of the seabed were observed. After 8.2 million m 3 of moderately contaminated dredged material had been dumped at the new dumping site Northwest, the species richness and abundance of benthic invertebrates declined over an area extending about 1-2 km eastwards. This correlated with a shift in sediment texture from sand to silt. The contamination of the fine sediment fraction at the Northwest location doubled. It is concluded that marine benthic resources at and around the dumping sites have been adversely affected by physical disturbance (burial, smothering). However, no causal link could be established with sediment-associated contaminants from the dredged spoils.
Thanks are due to Marie-Jos6 Steenwinkel (TNO), Joke Robinson, and Jan Hoekman (RIVM) for excelle... more Thanks are due to Marie-Jos6 Steenwinkel (TNO), Joke Robinson, and Jan Hoekman (RIVM) for excellent technical assistance.
Comparative Biochemistry and Physiology Part C: Toxicology & Pharmacology, 2004
Soil-living invertebrates are exposed to high concentrations of contaminants accumulating in dead... more Soil-living invertebrates are exposed to high concentrations of contaminants accumulating in dead organic matter, such as polycyclic aromatic hydrocarbons (PAHs). The capacity for PAH biotransformation is not equally developed in all invertebrates. In this paper, we compare three species of invertebrates, Porcellio scaber (Isopoda), Eisenia andrei (Lumbricidae) and Folsomia candida (Collembola), for the metabolites formed upon exposure to pyrene. Metabolic products of pyrene biotransformation in extracts from whole animals or isopod hepatopancreas were compared to those found in fish bile (flounder and plaice). An optimized HPLC method was used with fluorescence detection; excitation/emission spectra were compared to reference samples of 1-hydroxypyrene and enzymatically synthesized conjugates. Enzymatic hydrolysis after fractionation was used to demonstrate that the conjugates originated from 1-hydroxypyrene. All three invertebrates were able to oxidize pyrene to 1-hydroxypyrene, however, isopods and collembolans stood out as more efficient metabolizers compared to earthworms. In contrast to fish, none of the invertebrates produced pyrene-1-glucuronide as a phase II conjugate. Both Collembola and Isopoda produced significant amounts of pyrene-1-glucoside, whereas isopods also produced pyrene-1-sulfate. A third, previously unknown, conjugate was found in both isopods and springtails, and was analysed further using electrospray and atmospheric pressure chemical ionisation mass spectrometry. Based on the obtained mass spectra, a new conjugate is proposed: pyrene-1-O-(6&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;-O-malonyl)glucoside. The use of glucose-malonate as a conjugant in animal phase II biotransformation has not been described before, but is understandable in the microenvironment of soil-living invertebrates. In the earthworm, three other pyrene metabolites were observed, none of which was shared with the arthropods, although two were conjugates of 1-hydroxypyrene. Our study illustrates the great variety of the still unexplored metabolic diversity of invertebrate xenobiotic metabolism.
Unfortunately, the last author's name (R.O.) was spelled incorrectly. The correct name is Renata ... more Unfortunately, the last author's name (R.O.) was spelled incorrectly. The correct name is Renata Orinˇa´kova´.
An understanding of the conformational behavior of the stereoisomeric tetrols at the 11,12,13,14-... more An understanding of the conformational behavior of the stereoisomeric tetrols at the 11,12,13,14-positions of dibenzo[a,l]pyrene (DB[a,l]P) is essential for the spectroscopic identification of DNA adducts derived from the biologically highly active fjord region syn-and anti-DB[a,l]P-11,12-diol 13,14-epoxides. Conformational effects are expected to play an important role in DNA-DB[a,l]P diol epoxide reactivity, base-sequence specificity, and conformation dependent repair. The results of conformational studies on trans-anti-, cis-anti-, and cis-syn-DB[a,l]P tetrol isomers are presented and compared to the results obtained previously for trans-syn-DB[a,l]P tetrol (Carcinogenesis 17, 829-837, 1996). Molecular mechanics, dynamical simulations, and semiempirical calculations of electronic transitions are used to interpret the low-temperature fluorescence spectra and 1 H NMR data. Molecular dynamics simulations (in vacuo) identified two conformers (I and II) for each of the tetrol isomers; in all conformations the aromatic ring system is severely distorted. Fluorescence line-narrowing (FLN) spectroscopy identified two distinct conformational species for the transanti isomer, one occurring in ethanol and the other occurring in a glycerol/water matrix. The corresponding structures are assigned based on the S 1 r S 0 transition energies calculated for conformers I and II, respectively. 1 H NMR spectroscopy confirmed the structure of conformer I at room temperature. In contrast to trans-syn-DB[a,l]P tetrol (where the major conformation was identified as a boat structure), both conformations of trans-anti-DB[a,l]P tetrol feature a half-chair structure for the cyclohexenyl ring with different orientations of the hydroxyl groups. For cis-anti-and cis-syn-DB[a,l]P tetrols, only a single conformer is detected by FLN spectroscopy. The NMR results for the latter appear to be most consistent with a mixture of two half-chair conformers I and II, while for the cis-anti isomer a flattened, boatlike conformation was observed. The generally good agreement between the NMR coupling constants and those estimated theoretically indicates that these structures should serve as good starting points for spectroscopic or computational studies of DNA adducts derived from DB[a,l]P diol epoxides.
The nature of stable DNA adducts derived from the very potent carcinogen dibenzo[a,l]pyrene (DB[a... more The nature of stable DNA adducts derived from the very potent carcinogen dibenzo[a,l]pyrene (DB[a,l]P) in the presence of rat liver microsomes in vitro and in mouse skin in vivo has been studied using 32 P-postlabeling and laser-based fluorescence techniques. Analysis of DB[a,l]P-DNA adducts via 32 P-postlabeling has been obtained by comparison of the adduct patterns to those obtained from reactions of synthetic (()-anti-, (+)-anti-, (-)-anti-, and (()-syn-DB[a,l]P-11,12-diol 13,14-epoxide (DB[a,l]PDE) with single nucleotides and calf thymus DNA. anti-DB[a,l]PDE-dA adducts derived from the (-)-enantiomer are the major adducts formed in calf thymus DNA and in mouse skin DNA. The ratio of deoxyadenosine to deoxyguanosine modification is approximately 2:1 in mouse skin exposed to DB[a,l]P; activation by rat liver microsomes leads to a similar profile of adducts but with two additional spots. The conformations of DB[a,l]P adducts in native DNA, as well as the possibility of conformationdependent repair, have been explored by low-temperature fluorescence spectroscopy. These studies have been performed using polynucleotides and calf thymus DNA reacted in vitro with DB[a,l]PDE and native DNA from mouse epidermis exposed to DB[a,l]P. The results show that adducts are heterogeneous, possess different structures, and adopt different conformations. External, external but base-stacked and intercalated adduct conformations are observed in calf thymus DNA and in mouse skin DNA samples. Differences in adduct repair rates are also revealed; namely, the analysis of mouse skin DNA samples obtained at 24 and 48 h after exposure to DB[a,l]P clearly shows that external adducts are repaired more efficiently than intercalated adducts. These results, taken together with those for B[a]P-DNA adducts [Suh et al. (1995) Carcinogenesis 16, 2561-2569], indicate that the repair of DNA damage resulting from PAH diol epoxides is conformation-dependent.
One of the major DNA adducts from the extremely potent aromatic carcinogen dibenzo[a,/]pyrene (DB... more One of the major DNA adducts from the extremely potent aromatic carcinogen dibenzo[a,/]pyrene (DB[a,/]P) is the depurinating adduct syn-DB[a,/]P diolepoxide-14-N7Ade. Low-temperature fluorescence spectra of this adduct (and related derivatives bound to N3-adenine and N7-guanine) showed two distinct (0,0) origin bands with different excited-state vibrational frequencies, as measured by means of fluorescence line narrowing spectroscopy. The relative intensity of the two origin bands was solvent dependent The hypothesis that this phenomenon could be due to a conformational equilibrium was tested using molecular mechanics, dynamical simulations and semi-empirical quantum-mechanical calculations. The hydrolyzed metabolite DB[a,/]P tetraol was also studied for comparison. It was found that the syn-DB[a,/]P diolepoxide-14-N7Ade adduct is formed via trans addition to the epoxide. Exploration of the conformational space indeed produced two potential energy minima; both corresponding to structures in which the aromatic ring system is severely distorted. In conformation I the proximity of the distal ring forces the adenine base into a pseudo-axial position and the cyclohexenyl ring adopts a half-boat structure. In conformation II the distal ring is bent in the opposite direction, allowing the cyclohexenyl ring to adopt a half-chair structure with the base in a pseudo-equatorial position, partially stacked over the distal ring. The difference in (0,0) transition energy calculated for the two conformers agrees very well with the spectroscopic data, and the relative orientations of the hydrogens bound to the cyclohexenyl ring in the major (half-boat) conformation I are in full agreement with the experimentally observed proton NMR coupling constants.
The formation and repair of benzo[a]pyrene diol epoxide-N2-deoxyguanosine adducts (BPDE-N2-dG) in... more The formation and repair of benzo[a]pyrene diol epoxide-N2-deoxyguanosine adducts (BPDE-N2-dG) in DNA isolated from the skin of mice treated topically with benzo[a]pyrene (BP) was studied by 32P-postlabeling and by low-temperature fluorescence spectroscopy under low resolution and under high resolution fluorescence line narrowing (FLN) conditions. In agreement with earlier studies, total BP-DNA binding reached a maximum at 24 h after treatment (dose: 1 mumol/mouse), then declined rapidly until 4 days after treatment and much more slowly thereafter. An HPLC method was developed which resolved the 32P-postlabeled (-)-trans- from (-)-cis-anti-BPDE-N2-dG, and (+)-trans-from (+)-cis-anti-BPDE-N2-dG. High performance liquid chromatography analysis of the major TLC adduct spot (containing &gt; 80% of the total adducts) obtained by postlabeling BP-modified mouse skin DNA showed that it consisted of a major component that coeluted with (-)-cis-/(+)-trans-anti-BPDE-N2-dG and a minor component that coeluted with (-)-trans-/(+)-cis-anti-BPDE-N2-dG and that the minor component was repaired at a slower rate than the major component. Low-temperature fluorescence spectroscopy of the intact DNA identified the major adduct as (+)-trans-anti-BPDE-N2-dG and the minor adduct fraction consisted mainly of (+)-cis-anti-BPDE-N2-dG. In agreement with the 32P-postlabeling results it was observed by fluorescence spectroscopy that the (+)-cis-adducts were repaired more slowly than most other adducts. Moreover, the (+)-trans-adducts exhibited a broad distribution of base-stacked, partially base-stacked and helix-external conformations. Mouse skin DNA samples obtained at early timepoints (2-8 h) after treatment with BP contained substantially more of the &#39;external&#39; adducts, while samples at later timepoints (24-48 h) contained relatively more adducts in the base-stacked conformation, indicating also that the latter adducts are repaired less readily than the former. The possible biological significance of these novel observations of conformation-dependent rates of DNA adduct repair and their possible dependence on DNA sequence, are discussed.
In fish, metabolites of polycyclic aromatic compounds (PACs) in gall bladder bile can be used as ... more In fish, metabolites of polycyclic aromatic compounds (PACs) in gall bladder bile can be used as biomarkers for recent environmental exposure to PACs. These metabolites in the bile result from hepatic biotransformation processes whereby the lipophilic parent PACs are transformed in two steps (hydroxylation and subsequent conjugation) to more soluble forms and then passed to the gall bladder for elimination from the organism. As a biomarker of exposure, the determination of PAC metabolites in bile has several advantages over other assessment techniques. Several bile PACs are strong fluorophores and can thus be measured semi-quantitatively and very easily by means of straightforward fluorescence detection techniques. For example, fixed fluorescence detection and synchronous fluorescence scanning can be used for this purpose. These techniques are excellent for rapid screening of overall PAC exposure levels, but less suitable for the determination of individual compounds. The next level...
Fluorescence line-narrowing spectroscopy (FLNS) is a cryogenic technique that can be used to obta... more Fluorescence line-narrowing spectroscopy (FLNS) is a cryogenic technique that can be used to obtain high-resolution fluorescence spectra. The technique has mainly been used for fingerprint identification. However, this review focuses on the trend to use FLNS for probing purposes: obtaining information on interactions with the local environment or determining conformations. We briefly discuss the basics of FLNS, solute-matrix interactions and important instrumental aspects. We describe examples from various bioanalytical fields: DNA adducts of the aromatic carcinogen benzo[a]pyrene (BP); binding of BP metabolites to monoclonal antibodies or the estrogen receptor; FLNS studies of porphyrin-containing proteins; and, photosynthetic systems. As an illustration from the field of environmental chemistry, we discuss the use of luminescence line-narrowing spectroscopy-a special mode of FLNS-to study the complexation of lanthanides to humic substances.
The main objective of the EU-network is to bring together scientists with a background in analyti... more The main objective of the EU-network is to bring together scientists with a background in analytical chemistry interested in speciation method development with potential users from industry and representatives from legislative bodies. The network started on 1/10/1997 for a duration of 2 years. A series of meetings are being organised to debate all the important questions for collecting information on environmental, food and occupational health aspects of speciation and to define possible future projects. The findings and conclusions will be summarised as a series of general papers that will be published in the open literature, recapitulating the essential information gathered to date, outlining the state of the art for each topic and recommending legislative actions. A first meeting was held in Überlingen, Germany on 5-6 December 1997. The representatives from industry explained their interest in the network and the participants from the academic and national institutes gave a state-of-the-art
Conference on Lasers and Electro-Optics 2010, 2010
A variety of evanescent-wave cavity-enhanced techniques is used in studying interfacial kinetics ... more A variety of evanescent-wave cavity-enhanced techniques is used in studying interfacial kinetics as well as the performance of anti-biofouling coatings, demonstrating the potential of these techniques in label-free biosensing.
This article appeared in a journal published by Elsevier. The attached copy is furnished to the a... more This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/copyright
Deuteration effects on the vibronic structure of the emission and excitation spectra of triangula... more Deuteration effects on the vibronic structure of the emission and excitation spectra of triangular [4]phenylene (D 3h [4]phenylene) were studied using laser-excited Shpol'skii spectroscopy (LESS) in an octane matrix at 4.2 K. For correct assignment of the vibrational modes, the experimental results were compared with calculated frequencies (B3LYP/6-31G*). CH vibrations were identified by their characteristic isotopic shift in the spectra of deuterated triangular [4]phenylenes. Two CC stretching modes, at 100 cm-1 and 1176 cm-1 , suitable as probes for bond strength changes in the excited state, were identified. The isotope effect on the internal conversion rates of triangular [4]phenylene was evaluated from temperature dependent lifetime measurements. Isotope dependency and the magnitude of the internal conversion rates indicate that internal conversion in triangular [4]phenylene is most likely induced by CH vibrations. The results obtained by LESS and lifetime measurements were compared with PM3 PECI calculations of the excited state structure. The theoretical results and the relation between ground and excited state vibration energies of the 1176 cm-1 probe vibration indicate a reduction of bond alternation of the central cyclohexatriene ring in the excited state.
Vibrationally resolved fluorescence spectra of four angular [N]phenylenes were recorded with lase... more Vibrationally resolved fluorescence spectra of four angular [N]phenylenes were recorded with laser excited Shpol 'skii spectroscopy (LESS) in an n-octane matrix at 10 K. In general, the same vibrational frequencies were observed in the fluorescence excitation and emission spectra, indicating that the geometries of ground and electronically excited state are very similar. Because of intensity borrowing from the S 2 state, vibrations of two different symmetries were observed in the fluorescence excitation spectra of angular [3]phenylene and zigzag [5]phenylene. This finding allowed the location of the S 2 state for these compounds. DFT calculations (RB3LYP/6-31G*) of the ground state vibrational frequencies were made. The calculated vibrational modes were in reasonably good agreement with the experimental data. A new very low-frequency vibration of approximately 100 cm À1 was predicted and experimentally confirmed for all [N]phenylenes investigated. This vibration seems to be unique for [N]phenylenes and is attributed to an in-plane movement of the carbon backbone.
Organic contaminants [polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), polybro... more Organic contaminants [polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), polybrominated diphenylethers (PBDEs), nonylphenols], organotin compounds and trace metals (cadmium, chromium, mercury and zinc) were determined in flounder (Platichthys flesus) liver and sediment from the Amsterdam harbour (North Sea Canal) and Rotterdam harbour (Euromonding) and off the Dutch coast between the Amsterdam and Rotterdam harbour mouths in order to assess the level of contamination in these harbours and to study contamination gradients.
Tranexamic acid (TA) is a synthetic antifibrinolytic agent that is being considered as a candidat... more Tranexamic acid (TA) is a synthetic antifibrinolytic agent that is being considered as a candidate adjuvant drug for site-specific pharmaco-laser therapy of port wine stains. For drug utility studies, a high-performance liquid chromatography (HPLC)-fluorescence method was developed for the quantification of TA in blood. Platelet-poor plasma was prepared, size-separated using 3 kDa cutoff centrifuge filters, and derivatized with naphthalene-2-3-dicarboxaldehyde (NDA) and cyanide. The excess of NDA was quenched after 2 min by adding tryptophan. The derivatives were separated on a 2.1 mm C18 column using an acetate buffer/acetonitrile gradient. Excellent separation from plasma background was obtained at pH 5.5. Quantification was carried out at 440/520 nm. The limit of detection was 0.5 M and the mean ± SD recovery from whole blood was 81.7 ± 10.9%. Derivatized TA samples were stable for at least 36 h at 4 • C. The method was successfully applied to a heat-induced TA release study from thermosensitive liposomes.
With 15 flavonoids as test compounds, the analytical performance of four modes of LC-MS, multiple... more With 15 flavonoids as test compounds, the analytical performance of four modes of LC-MS, multiple MS (MS) and tandem MS operation (atmospheric pressure chemical ionization (APCI), electrospray ionization, positive and negative ionization) was compared for two mass spectrometers, a triple-quadrupole and an ion-trap instrument. Two organic modifiers, methanol and acetonitrile, and two buffers, ammonium acetate and ammonium formate, were used. In general, the use of APCI in the negative ion mode gave the best response, with the signal intensities and the mass-spectral characteristics not differing significantly between the two instruments. The best results were obtained when methanol-ammonium formate (pH 4.0) was used as LC eluent. Under optimum conditions full-scan limits of detection of 0.1-30 mg / l were achieved in the negative APCI mode. Here it needs to be emphasized that up to 2-order response differences were found both between analytes and between modes of ionization. This implies that one should be very cautious when interpreting data on the n screening of real-life samples. The main fragmentations observed in the MS spectra on the ion-trap, or the tandem MS spectra on the triple-quadrupole were generally the same. The advantage of the former approach is the added possibility to ascertain precursor→product ion relationships.
Utilizing the concept of shear-driven chromatography, we have been able to realize reversed-phase... more Utilizing the concept of shear-driven chromatography, we have been able to realize reversed-phase LC separations in flat rectangular nano-channels coated with a C8 monolayer and being as thin as 100 nm. At this scale, the separation kinetics are strongly enhanced, as is witnessed by the extremely short time (&lt; 0.1 s) needed to separate a mixture of coumarin dyes. The observed plate numbers are still relatively small, because the experiments were conducted in ultra-short columns (&lt; or = 1 mm) and under injection band width-limiting conditions.
The environmental impact and recovery associated with the long and uninterrupted disposal of larg... more The environmental impact and recovery associated with the long and uninterrupted disposal of large volumes of moderately contaminated dredged material from the port of Rotterdam was studied at nearby dumping sites in the North Sea. Observations were made on sediment contamination, ecotoxicity, biomarker responses and benthic community changes shortly after dumping at the 'North' site had ceased and at the start of disposal at the new dumping site 'Northwest'. During the period of dumping, very few benthic invertebrates were found at the North site. Concentrations of cadmium, mercury, polychlorinated biphenyls (PCBs), polyaromatic hydrocarbons (PAHs) and tributyltin (TBT) in the fine sediment fraction (< 63 mm) from this site were 2-3 times higher than at the reference site. In four different bioassays with marine invertebrates the sediments showed no acute toxic effects. In tissue (pyloric caeca) of resident starfish Asterias rubens, residual levels of mercury, zinc, PCBs and dioxin-like activity were never more than twice those at the reference site. Four different biomarkers (DNA integrity, cytochrome P450 content, benzo[a]pyrene hydroxylase activity and acetylcholinesterase inhibition) were used on the starfish tissues, but no significant differences were found between North and the reference site. Minor pathological effects were observed in resident dab Limanda limanda. One year after dumping had ceased at the North site, a significant increase in the species richness and abundance of benthic invertebrates and a concomitant decrease in the fine sediment fraction of the seabed were observed. After 8.2 million m 3 of moderately contaminated dredged material had been dumped at the new dumping site Northwest, the species richness and abundance of benthic invertebrates declined over an area extending about 1-2 km eastwards. This correlated with a shift in sediment texture from sand to silt. The contamination of the fine sediment fraction at the Northwest location doubled. It is concluded that marine benthic resources at and around the dumping sites have been adversely affected by physical disturbance (burial, smothering). However, no causal link could be established with sediment-associated contaminants from the dredged spoils.
Thanks are due to Marie-Jos6 Steenwinkel (TNO), Joke Robinson, and Jan Hoekman (RIVM) for excelle... more Thanks are due to Marie-Jos6 Steenwinkel (TNO), Joke Robinson, and Jan Hoekman (RIVM) for excellent technical assistance.
Comparative Biochemistry and Physiology Part C: Toxicology & Pharmacology, 2004
Soil-living invertebrates are exposed to high concentrations of contaminants accumulating in dead... more Soil-living invertebrates are exposed to high concentrations of contaminants accumulating in dead organic matter, such as polycyclic aromatic hydrocarbons (PAHs). The capacity for PAH biotransformation is not equally developed in all invertebrates. In this paper, we compare three species of invertebrates, Porcellio scaber (Isopoda), Eisenia andrei (Lumbricidae) and Folsomia candida (Collembola), for the metabolites formed upon exposure to pyrene. Metabolic products of pyrene biotransformation in extracts from whole animals or isopod hepatopancreas were compared to those found in fish bile (flounder and plaice). An optimized HPLC method was used with fluorescence detection; excitation/emission spectra were compared to reference samples of 1-hydroxypyrene and enzymatically synthesized conjugates. Enzymatic hydrolysis after fractionation was used to demonstrate that the conjugates originated from 1-hydroxypyrene. All three invertebrates were able to oxidize pyrene to 1-hydroxypyrene, however, isopods and collembolans stood out as more efficient metabolizers compared to earthworms. In contrast to fish, none of the invertebrates produced pyrene-1-glucuronide as a phase II conjugate. Both Collembola and Isopoda produced significant amounts of pyrene-1-glucoside, whereas isopods also produced pyrene-1-sulfate. A third, previously unknown, conjugate was found in both isopods and springtails, and was analysed further using electrospray and atmospheric pressure chemical ionisation mass spectrometry. Based on the obtained mass spectra, a new conjugate is proposed: pyrene-1-O-(6&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;-O-malonyl)glucoside. The use of glucose-malonate as a conjugant in animal phase II biotransformation has not been described before, but is understandable in the microenvironment of soil-living invertebrates. In the earthworm, three other pyrene metabolites were observed, none of which was shared with the arthropods, although two were conjugates of 1-hydroxypyrene. Our study illustrates the great variety of the still unexplored metabolic diversity of invertebrate xenobiotic metabolism.
Unfortunately, the last author's name (R.O.) was spelled incorrectly. The correct name is Renata ... more Unfortunately, the last author's name (R.O.) was spelled incorrectly. The correct name is Renata Orinˇa´kova´.
An understanding of the conformational behavior of the stereoisomeric tetrols at the 11,12,13,14-... more An understanding of the conformational behavior of the stereoisomeric tetrols at the 11,12,13,14-positions of dibenzo[a,l]pyrene (DB[a,l]P) is essential for the spectroscopic identification of DNA adducts derived from the biologically highly active fjord region syn-and anti-DB[a,l]P-11,12-diol 13,14-epoxides. Conformational effects are expected to play an important role in DNA-DB[a,l]P diol epoxide reactivity, base-sequence specificity, and conformation dependent repair. The results of conformational studies on trans-anti-, cis-anti-, and cis-syn-DB[a,l]P tetrol isomers are presented and compared to the results obtained previously for trans-syn-DB[a,l]P tetrol (Carcinogenesis 17, 829-837, 1996). Molecular mechanics, dynamical simulations, and semiempirical calculations of electronic transitions are used to interpret the low-temperature fluorescence spectra and 1 H NMR data. Molecular dynamics simulations (in vacuo) identified two conformers (I and II) for each of the tetrol isomers; in all conformations the aromatic ring system is severely distorted. Fluorescence line-narrowing (FLN) spectroscopy identified two distinct conformational species for the transanti isomer, one occurring in ethanol and the other occurring in a glycerol/water matrix. The corresponding structures are assigned based on the S 1 r S 0 transition energies calculated for conformers I and II, respectively. 1 H NMR spectroscopy confirmed the structure of conformer I at room temperature. In contrast to trans-syn-DB[a,l]P tetrol (where the major conformation was identified as a boat structure), both conformations of trans-anti-DB[a,l]P tetrol feature a half-chair structure for the cyclohexenyl ring with different orientations of the hydroxyl groups. For cis-anti-and cis-syn-DB[a,l]P tetrols, only a single conformer is detected by FLN spectroscopy. The NMR results for the latter appear to be most consistent with a mixture of two half-chair conformers I and II, while for the cis-anti isomer a flattened, boatlike conformation was observed. The generally good agreement between the NMR coupling constants and those estimated theoretically indicates that these structures should serve as good starting points for spectroscopic or computational studies of DNA adducts derived from DB[a,l]P diol epoxides.
The nature of stable DNA adducts derived from the very potent carcinogen dibenzo[a,l]pyrene (DB[a... more The nature of stable DNA adducts derived from the very potent carcinogen dibenzo[a,l]pyrene (DB[a,l]P) in the presence of rat liver microsomes in vitro and in mouse skin in vivo has been studied using 32 P-postlabeling and laser-based fluorescence techniques. Analysis of DB[a,l]P-DNA adducts via 32 P-postlabeling has been obtained by comparison of the adduct patterns to those obtained from reactions of synthetic (()-anti-, (+)-anti-, (-)-anti-, and (()-syn-DB[a,l]P-11,12-diol 13,14-epoxide (DB[a,l]PDE) with single nucleotides and calf thymus DNA. anti-DB[a,l]PDE-dA adducts derived from the (-)-enantiomer are the major adducts formed in calf thymus DNA and in mouse skin DNA. The ratio of deoxyadenosine to deoxyguanosine modification is approximately 2:1 in mouse skin exposed to DB[a,l]P; activation by rat liver microsomes leads to a similar profile of adducts but with two additional spots. The conformations of DB[a,l]P adducts in native DNA, as well as the possibility of conformationdependent repair, have been explored by low-temperature fluorescence spectroscopy. These studies have been performed using polynucleotides and calf thymus DNA reacted in vitro with DB[a,l]PDE and native DNA from mouse epidermis exposed to DB[a,l]P. The results show that adducts are heterogeneous, possess different structures, and adopt different conformations. External, external but base-stacked and intercalated adduct conformations are observed in calf thymus DNA and in mouse skin DNA samples. Differences in adduct repair rates are also revealed; namely, the analysis of mouse skin DNA samples obtained at 24 and 48 h after exposure to DB[a,l]P clearly shows that external adducts are repaired more efficiently than intercalated adducts. These results, taken together with those for B[a]P-DNA adducts [Suh et al. (1995) Carcinogenesis 16, 2561-2569], indicate that the repair of DNA damage resulting from PAH diol epoxides is conformation-dependent.
One of the major DNA adducts from the extremely potent aromatic carcinogen dibenzo[a,/]pyrene (DB... more One of the major DNA adducts from the extremely potent aromatic carcinogen dibenzo[a,/]pyrene (DB[a,/]P) is the depurinating adduct syn-DB[a,/]P diolepoxide-14-N7Ade. Low-temperature fluorescence spectra of this adduct (and related derivatives bound to N3-adenine and N7-guanine) showed two distinct (0,0) origin bands with different excited-state vibrational frequencies, as measured by means of fluorescence line narrowing spectroscopy. The relative intensity of the two origin bands was solvent dependent The hypothesis that this phenomenon could be due to a conformational equilibrium was tested using molecular mechanics, dynamical simulations and semi-empirical quantum-mechanical calculations. The hydrolyzed metabolite DB[a,/]P tetraol was also studied for comparison. It was found that the syn-DB[a,/]P diolepoxide-14-N7Ade adduct is formed via trans addition to the epoxide. Exploration of the conformational space indeed produced two potential energy minima; both corresponding to structures in which the aromatic ring system is severely distorted. In conformation I the proximity of the distal ring forces the adenine base into a pseudo-axial position and the cyclohexenyl ring adopts a half-boat structure. In conformation II the distal ring is bent in the opposite direction, allowing the cyclohexenyl ring to adopt a half-chair structure with the base in a pseudo-equatorial position, partially stacked over the distal ring. The difference in (0,0) transition energy calculated for the two conformers agrees very well with the spectroscopic data, and the relative orientations of the hydrogens bound to the cyclohexenyl ring in the major (half-boat) conformation I are in full agreement with the experimentally observed proton NMR coupling constants.
The formation and repair of benzo[a]pyrene diol epoxide-N2-deoxyguanosine adducts (BPDE-N2-dG) in... more The formation and repair of benzo[a]pyrene diol epoxide-N2-deoxyguanosine adducts (BPDE-N2-dG) in DNA isolated from the skin of mice treated topically with benzo[a]pyrene (BP) was studied by 32P-postlabeling and by low-temperature fluorescence spectroscopy under low resolution and under high resolution fluorescence line narrowing (FLN) conditions. In agreement with earlier studies, total BP-DNA binding reached a maximum at 24 h after treatment (dose: 1 mumol/mouse), then declined rapidly until 4 days after treatment and much more slowly thereafter. An HPLC method was developed which resolved the 32P-postlabeled (-)-trans- from (-)-cis-anti-BPDE-N2-dG, and (+)-trans-from (+)-cis-anti-BPDE-N2-dG. High performance liquid chromatography analysis of the major TLC adduct spot (containing &gt; 80% of the total adducts) obtained by postlabeling BP-modified mouse skin DNA showed that it consisted of a major component that coeluted with (-)-cis-/(+)-trans-anti-BPDE-N2-dG and a minor component that coeluted with (-)-trans-/(+)-cis-anti-BPDE-N2-dG and that the minor component was repaired at a slower rate than the major component. Low-temperature fluorescence spectroscopy of the intact DNA identified the major adduct as (+)-trans-anti-BPDE-N2-dG and the minor adduct fraction consisted mainly of (+)-cis-anti-BPDE-N2-dG. In agreement with the 32P-postlabeling results it was observed by fluorescence spectroscopy that the (+)-cis-adducts were repaired more slowly than most other adducts. Moreover, the (+)-trans-adducts exhibited a broad distribution of base-stacked, partially base-stacked and helix-external conformations. Mouse skin DNA samples obtained at early timepoints (2-8 h) after treatment with BP contained substantially more of the &#39;external&#39; adducts, while samples at later timepoints (24-48 h) contained relatively more adducts in the base-stacked conformation, indicating also that the latter adducts are repaired less readily than the former. The possible biological significance of these novel observations of conformation-dependent rates of DNA adduct repair and their possible dependence on DNA sequence, are discussed.
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Papers by F. Ariese