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PubMed1998

Ability of 16 priority PAHs to be directly cytotoxic to a cell line from the rainbow trout gill.

Sixteen polycyclic aromatic hydrocarbons (PAHs) were screened for their ability to be directly cytotoxic to a cell line from the rainbow trout gill, RTgill-W1. Exposure times of 2 h or less were sufficient for direct cytotoxicity to be detected, which appeared to be caused by a common mechanism, the general perturbation of membranes. This was judged by the similarity of results obtained for three fluorescent indicator dyes, alamar Blue, 5-carboxyfluorescein diacetate acetoxymethyl ester (CFDA-AM) and neutral red. Among the 16 PAHs tested, just two- and three-ring PAHs were found to be directly cytotoxic. These were naphthalene approximately = acenaphthylene approximately = acenaphthene > fluorene approximately = phenanthrene. The results suggest that water solubility and lipophilicity are the critical properties determining the direct cytotoxicity of PAHs and that they do so by influencing PAH accumulation in membranes. Only naphthalene was effective at concentrations well below its water solubility limit. Therefore, direct cytotoxicity is likely to be most environmentally relevant only with naphthalene.

Acenaphthenes↗
PubMed1997

Alterations in epidermal growth factor binding to hepatic membranes following dietary exposure of rats to known hepatocarcinogens.

Administration of the chemical carcinogen 2-acetylaminofluorene (2-AAF) has previously been shown to lower hepatic epidermal growth factor (EGF) binding levels during chemically induced hepatocarcinogenesis. To further characterize the specificity of this response, EGF binding levels for liver microsomes were determined after a 3-week administration of subacute doses of 2-AAF and five other known hepatocarcinogens: 3'-methyl-4-dimethylaminoazobenzene (3'Me-DAB), 2-AAF, aflatoxin B1 (AFB1), thioacetamide (TA), ethionine, benzidine (Benz), as well as four non-hepatocarcinogens: fluorene, p-aminoazobenzene, 4-acetylaminofluorene (4-AAF), and 3-methylcholanthrene. Five of six of the hepatocarcinogens tested (3'Me-DAB, 2-AAF, TA, AFB1 and Benz) caused significant lowering of EGF binding levels, and one of the four non-hepatocarcinogens (4-AAF) caused significant lowering of EGF binding levels. Paired feeding studies indicated that the decreases in EGF binding levels were not a result of differences in net diet consumption. These findings show that decreases in EGF binding capacity are caused by a diverse group of known hepatocarcinogenic compounds at an early stage in the carcinogenesis process.

2-Acetylaminofluorene↗
PubMed1988

Direct absorptiometric quantitation in high-performance liquid chromatography in the absence of concomitant reference standards.

A method for absorptiometric quantification in high-performance liquid chromatography that utilizes the known molar absorption coefficients of the individual components of a mixture of analytes to enable a series of determinations to be carried out without the concomitant use of reference standards is described. An equation is derived that describes the dependence of the molar amount of a defined analyte on the parameters influencing the detector response and on the peak area of the analyte in the chromatogram. The equation can be used for the direct calculation of the molar amount of individual analytes in a well resolved mixture. A method for the analysis of two analytes, the peaks of which totally overlap but which differ by their molar absorption coefficients, is also described. The validity of the equations and the applicability of the proposed method was examined in the analysis of 5-(2-dimethylaminoethoxy)-7-oxo-7H-benzo[c]fluorene hydrochloride (benflurone) and its metabolites. Some examples of the application of this approach are considered.

Chemical Phenomena↗
PubMed2001

Detection of drug-induced, superoxide-mediated cell damage and its prevention by antioxidants.

The mode of the cytotoxic activity of three benzo(c)fluorene derivatives was characterized. The observed morphological changes of lysosomes or variations of mitochondrial activity are assumed to be the consequence of cell protection against oxidative damage and/or the part of the damage process. To establish the relationship between the quantity of superoxide (O2*-) generated and the degree of damage resulting from O2*-, a simple system based on measurement of 3-(4-iodophenyl)-2-(4-nitrophenyl)-5-phenyltetrazolium chloride (INT) reductase activity in the presence of superoxide dismutase (SOD) was used. The functionality of the chosen battery of in vitro tests was proved using several known superoxide inducers: cyclosporin A (CsA) and benzo(a)pyrene (BP), as well as noninducers: citrinin (CT) and cycloheximide (CH). From the results followed that the cell growth tests are much better indices of toxicity than the other tests. The model system for the evaluation of the protective capacity of antioxidants against superoxide-induced cytotoxicity included simultaneous exposure of HeLa cells to cytotoxic drugs and to quercetin (Qe), an antioxidant of plant origin. The complete abolishment of the inhibition of cell proliferation and clonogenic survival was concluded to be due to the protective effect of the antioxidant. These observations correlated with the decrease of superoxide content as estimated by the INT-reductase assay in the presence of SOD using the same model system, as well as with the increase of intracellular SOD content and its activity.

Antioxidants↗
PubMed1999

Transplantation of fetal liver tissue suspension into the spleens of adult syngenic rats: effects of various mitogens and cytotoxins on cytochrome P450 (P450) isoforms expression and on P450 mediated monooxygenase functions.

Syngenic fetal liver tissue suspensions were transplanted into the spleens of adult male Fisher 344 inbred rats. Four months after surgery, transplant recipients and age matched control rats were treated with various mitogens (fluorene [FEN], fluorenone [FON] and 2-acetylaminofluorene [AAF]) or cytotoxins (allyl alcohol [AAL], bromobenzene [BBZ] and carbon tetrachloride [CCl4]) or the respective solvents 24 or 48 hours before sacrifice. The expression of three cytochrome P450 (P450) isoforms, 1A1, 2B1 and 3A2, within spleens and livers was assessed by immunohistochemistry and P450 mediated monooxygenase functions in spleen and liver 9000 g supernatants by the model reactions ethoxyresorufin O-deethylation (EROD), ethoxycoumarin O-deethylation (ECOD), and ethylmorphine N-demethylation (EMND). The orthotopic livers of both solvent treated transplant recipients and control rats displayed only in few lobules a slight P450 1A1, but in all lobules a moderate P450 2B1 and 3A2 expression, all mainly located in the hepatocytes around the central veins. Correspondingly, regular EROD, ECOD and EMND activities were observed. Each of the three mitogens increased the P450 1A1 expression in the hepatocytes of the perivenous zones of the liver lobules. FON administration caused an additional P450 1A1 immunostaining in the periportal areas, and AAF treatment a P450 1A1 expression in bile duct epithelia. Also the staining for P450 2B1 and 3A2 in the hepatocytes of the perivenous and intermediate zones of the liver lobules was intensified after treatment with any of the mitogens. The three model reactions were significantly increased within the livers after FEN and FON administration, whereas after AAF treatment only ECOD was enhanced, EROD remained unaffected and EMND was decreased. The cytotoxin AAL caused small lesions and fatty degeneration of hepatocytes only in some periportal areas. BBZ only produced a perivenous necrosis of single cells, whereas CCl4 caused complete necrosis of the centrilobular parenchyma. Immunohistochemically, AAL administration led to an increase in the P450 2B1 expression in the perivenous hepatocytes, whereas the staining for P450 1A1 was not affected and that for P450 3A2 was even decreased in the periportal areas. Due to AAL treatment EROD and EMND activities were not affected and ECOD activity was increased. BBZ administration caused a P450 1A1 expression in the periportal hepatocytes but a decrease in this staining of the perivenous cells. The number of hepatocytes positively stained for P450 2B1 and 3A2 in the perivenous and intermediate zones was diminished in comparison to the livers of solvent treated rats. After BBZ treatment, EROD and EMND activities were decreased, ECOD activity was not affected. CCl4 administration caused a strong reduction in the expression of all three P450 isoforms and in the activity of all three model reactions. Spleens of control rats displayed almost no P450 isoforms expression and P450 mediated monooxygenase functions, without as well as after treatment with the mitogens or cytotoxins. Similar to adult liver, the hepatocytes in the transplant containing spleens showed nearly no P450 1A1, but a noticeable P450 2B1 and 3A2 expression. No staining was observed within the bile duct cells of the intrasplenic transplants.

2-Acetylaminofluorene↗
PubMed1999

Use of rat hepatocytes immobilized in agarose gel threads for biosynthesis of metabolites of potential cytostatics.

The aim of this work was to evaluate possibility of use of the rat isolated hepatocytes immobilized in agarose gel and continuously perfused for production of needed metabolites of two potential cytostatics, benfluron (5-(2-dimethylamino-ethoxy)-7-oxo-7H-benzo[c]fluorene) and oracin (6-[2-(hydroxyethyl) amino-ethyl]-5,11-dioxo-5,6-dihydro-11H-indeno [1,2-c]isoquinoline). The rat isolated hepatocytes obtained by two-step collagenase perfusion method were immobilized in agarose threads and perfused in a small bioreactor under a recirculation regimes. Biosynthesis of 9-hydroxybenfluron and 3-hydroxyoracin in immobilized rat hepatocytes was studied. Yields of the metabolites of interest in hepatocytes in immobilized and perfused rat hepatocytes was compared to production of metabolites in hepatocyte suspension and in rats in vivo. 9-hydroxybenfluron was presented during perfusion of immobilized rat hepatocytes in a relatively high amounts but total recovery all forms of benfluron was very low due to especially high binding to components of the perfusion system. More effective method remains the production of 9-hydroxybenfluron in rats in vivo. A considerable biosynthesis of 3-hydroxyoracin by immobilized rat hepatocytes in the bioreactor was found. Concentration of the metabolite in the perfusate rose continuously during 6 hours of perfusion. 3-hydroxyoracin production was increased several times with use of immobilized hepatocytes from rats treated for three days with methylcholanthrene. The yield of 3-hydroxyoracin in rats in vivo was comparably high but an advantage of in vitro synthesis is a much shorter interval to obtain the same amount of the metabolite of interest. In spite of some limitations in compounds exerting high trapping in the perfusion system, the method of the immobilized and perfused hepatocytes can be very useful and effective for production of some drug metabolites in biochemistry and pharmacology.

Animals↗
PubMed2001

Structure-activity relationships and optimisation of the selective MDR modulator 2-(3,4-dimethoxyphenyl)-5-(9-fluorenylamino)-2-(methylethyl) pentanenitrile and its N-methyl derivative.

Several ring-substituted derivatives of previously studied MDR inhibitors 2-(3,4-dimethoxyphenyl)-5-(9-fluorenylamino)-2-(methylethyl)pentanenitrile and 2-(3,4-dimethoxyphenyl)-5-[(9-fluorenyl)-N-methylamino]-2-(methylethyl)pentanenitrile have been synthesised and studied with the aim of optimising activity and selectivity. The results show that MDR inhibition is scarcely sensitive to modulation of the electronic properties of the fluorene ring. Even if dramatic improvement was not obtained, one of the compounds (2) showed improved potency and selectivity with respect to the leads and appears to be a better candidate for drug development.

Animals↗
PubMed2001

[Theoretical simulation of UV absorption spectra of carbazole and some homocyclic analogs].

The UV absorption spectra structures of carbazole, fluorene and dibenzofurane are studied using the atom monopole-dipole interaction (AMDI) model and atomic dipolar polarisabilities and effective charge given by Fraga. The absorption spectra corresponding to these molecules and their self-associations are presented. The original obtained results are discussed and compared to previous works.

Benzofurans↗
PubMed2001

Laboratory spectra of cold gas phase polycyclic aromatic hydrocarbon cations, and their possible relation to the diffuse interstellar bands.

A novel laboratory technique is described, combining the use of supersonic expansion, laser excitation and small aromatic-rare gas van der Waals (vdW) clusters properties, which was developed to access the electronic absorption spectra of the polycyclic aromatic hydrocarbon (PAH) cations in the visible. It consists in preparing vdW complexes of the PAH molecule with a rare gas in a molecular beam, to photoionize it by resonant selective two-photon ionization, then to photodissociate this ionic complex by means of a delayed laser pulse in a time-of-flight mass spectrometer. The method is illustrated by presenting the visible spectra of the Naphthalene, Phenanthrene, Fluorene and Phenylacetylene cations. Such spectra can be unambiguously compared to the astronomical spectra of reddened stars, which exhibit the so-called diffuse interstellar bands (DIBs) in absorption. An interesting feature of the technique is its ability to measure the absolute absorption cross-sections. The large values of the oscillator strengths of the transitions, which are derived, are discussed in the astrophysical context which consists in considering that the PAH cations could be carriers for some of the DIBs.

Acetylene↗
PubMed2006

UV excitation thermal lens microscope for sensitive and nonlabeled detection of nonfluorescent molecules.

An ultrasensitive and nonlabeled detection method of nonfluorescent molecules on a microchip was developed by realizing a thermal lens microscope (TLM) with a 266-nm UV pulsed laser as an excitation light source (UV-TLM). Pulsed laser sources have advantages over continuous-wave laser sources in more compact size and better wavelength tuning, which are important for microchip-based analytical systems. Their disadvantage is difficulty in applying a lock-in amplifier due to the high (>10(4)) duty ratio of pulse oscillation. To overcome this problem, we realized a quasi-continuous-wave excitation by modulating the pulse trains at approximately 1 kHz and detecting the synchronous signal with a lock-in amplifier. The optimum pulse repetition frequency was obtained at 80 kHz, which was reasonable considering thermal equilibrium time. Furthermore, a permissible flow velocity in the range of 6.6-19.8 mm/s was found to avoid sensitivity decrease due to photochemical reactions and thermal energy dissipation. Under these conditions, we detected adenine aqueous solutions on a fused-silica microchip without labeling and obtained a sensitivity that was 350 times higher than that in a spectrophotometric method. The sensitivity was enough for detection on a microchip with an optical path length that was 2-3 orders shorter than that in conventional cuvettes. Finally, the UV-TLM method was applied to liquid chromatography detection. Fluorene and pyrene were separated in a microcolumn and detected in a capillary (50-microm inner diameter) with 150 times higher sensitivity than a spectrophotometric method. Our method provides highly sensitive and widely applicable detections for various analytical procedures and chemical syntheses on microchips.

Adenine↗
PubMed2006

Determination of the structure and orientation of organic molecules tethered to flat graphitic carbon by ATR-FT-IR and Raman spectroscopy.

Mono- and multilayers of nitroazobenzene (NAB), azobenzene (AB), nitrobiphenyl (NBP), biphenyl (BP), and fluorene (FL) were covalently bonded to flat pyrolyzed photoresist films (PPF) by electrochemical reduction of their diazonium derivatives. The structure and orientation of the molecular layers were probed with ATR-FT-IR and Raman spectroscopy. A hemispherical germanium ATR element used with p-polarized light at 65 degrees incidence angle yielded high signal/noise IR spectra for monolayer coverage of molecules on PPF. The IR spectra are dominated by in-plane vibrational modes in the 1000-2000-cm(-1) spectral range but also exhibit weaker out-of-plane deformations in the 650-1000-cm(-1) region. The average tilt angle with respect to the surface normal for the various molecules varied from 31.0 +/- 4.5 degrees for NAB to 44.2 +/- 5.4 degrees for FL with AB, NBP, and BP exhibiting intermediate adsorption geometries. Raman intensity ratios of NAB and AB for p- and s-polarized incident light support the conclusion that the chemisorbed molecules are in a predominantly upright orientation. The results unequivocally indicate that molecules electroreduced from their diazonium precursors are not chemisorbed flat on the PPF surface, but rather at an angle, similar to the behavior of Au/thiol self-assembled monolayers, Langmuir-Blodgett films, and porphyrin molecules chemisorbed thermally on silicon and PPF from alkyne and alkene precursors.

Azo Compounds↗
PubMed1995

Solution conformation of [AF]dG opposite a -1 deletion site in a DNA duplex: intercalation of the covalently attached aminofluorene ring into the helix with base displacement of the C8-modified Syn guanine into the major groove.

This paper reports on the solution structure of the [AF]dG adduct positioned opposite a deletion site in a DNA oligomer duplex that defines the alignment of the covalent aminofluorene--C8-guanine adduct relative to the deletion site. The combined NMR molecular mechanics computational studies were undertaken on the [AF]dG adduct embedded in the d(C5-[AF]G6-C7).d(G16-G17) sequence context in a duplex containing 11 residues on the modified strand and 10 on the partner, with no base opposite the modification. The exchangeable and nonexchangeable protons of the aminofluorene moiety and the nucleic acid were assigned following analysis of two-dimensional NMR data sets in H2O and D2O solution. The solution conformation of the [AF]G.del 11-mer duplex has been determined by incorporating intramolecular and intermolecular proton-proton distances defined by lower and upper bounds deduced from NOESY spectra as restraints in molecular mechanics computations in torsion angle space. The aminofluorene ring of [AF]dG6 is intercalated between intact Watson-Crick dC5.dG17 and dC7.dG16 base pairs with the guanine base of [AF]dG6 in a syn alignment displaced into the major groove. The syn glycosidic torsion angle at [AF]dG6 is supported by both carbon and proton chemical shift data for the sugar resonances of the modified guanine residue. The long axis of the aminofluorene ring is parallel to the long axis of the flanking dG.dC base pairs with the AF ring undergoing rapid 180 degrees flips on the NMR time scale. The intercalation site is wedge shaped with a pronounced propeller-twisting and buckling of the dC5.dG17 base pair. The guanine base of [AF]dG6, which is positioned in the major groove, is inclined relative to the helix axis and stacks over the 5'-flanking dC5 residue in the solution structure. The intercalative-base displacement structure of the [AF]dG.del 11-mer duplex exhibits several unusually shifted proton resonances that can be readily accounted for by the ring current contributions of the guanine purine and carcinogen fluorene aromatic rings of the [AF]dG6 adduct. There are similarities between this structure of the AF-C8-dG covalent adduct positioned opposite a deletion site and the (+)-trans-anti-BP-N2-dG covalent adduct positioned opposite a deletion site in the same sequence context reported previously from this laboratory [Cosman et al. (1994) Biochemistry 33, 11507-11517]. The chromophores are intercalated into the helix opposite the deletion site with displacement of the modified guanine into the major groove in both cases.(ABSTRACT TRUNCATED AT 400 WORDS)

Base Sequence↗
PubMed1995

Solution conformation of [AF]dG opposite a -2 deletion site in a DNA duplex: intercalation of the covalently attached aminofluorene ring into the helix with base displacement of the C8-modified syn guanine and adjacent unpaired 3'-adenine into the major groove.

This paper reports the solution conformation of the covalent aminofluorene-C8-deoxyguanosine [AF]dG adduct positioned opposite a -2 deletion site in a DNA oligomer duplex. The combined NMR and molecular mechanics computational studies were undertaken on the [AF]dG adduct embedded in the d(C5-[AF]G6-A7-C8).d(G17-G18) sequence context in a duplex containing 12 residues on the modified strand and 10 on the partner strand, with no bases opposite the [AF]dG6-dA7 segment. The exchangeable and nonexchangeable protons of the aminofluorene moiety and the nucleic acid were assigned following analysis of two-dimensional NMR data sets in H2O and D2O solution. The solution conformation of the [AF]dG.2del 12-mer duplex has been determined by incorporating intramolecular and intermolecular proton-proton distances defined by upper and lower bounds deduced from NOESY spectra as restraints in molecular mechanics computations in torsion angle space. The aminofluorene ring of [AF]dG6 is intercalated between intact Waston-Crick dC5.dG18 and dC8.dG17 base pairs with the deoxyguanosine base of [AF]dG6 in a syn alignment displaced into the major groove. The syn glycosidic torsion angle at [AF]dG6 is supported by both carbon and proton chemical shift data for the sugar resonances of the modified deoxyguanosine residue. The unpaired dA7 base is also looped out of the helix into the major groove with the purine rings of [AF]dG6 and dA7 stacking on each other in the groove. The long axis of the intercalated aminofluorene ring is parallel to the long axis of the flanking dG.dC base pairs. The intercalation site is wedge shaped with a pronounced propeller-twisting and buckling of the dC5.dG18 base pair. The deoxyguanosine base of [AF]dG6, which is positioned in the major groove, is inclined relative to the helix axis and stacks over the 5'-flanking dC5 residue in the solution structure. The intercalative base displacement structure of the [AF]dG.2del 12-mer duplex exhibits several unusually shifted proton resonances that can be readily accounted for by the ring current contributions of the deoxyguanosine purine and carcinogen fluorene aromatic rings of the [AF]dG6 adduct. We note similarities between the present conformation of [AF]dG positioned opposite a -2 deletion site with our earlier conformational studies of [AF]dG positioned opposite a -1 deletion site [Mao, B., Cosman, M., Hingerty, B. E., Broyde, S., & Patel, D. J. (1995) Biochemistry 34, 6226-6238]. For both conformations, the aminofluorene carcinogen inserts into the helix at the deletion site through base displacement of the modified deoxyguanosine in a syn alignment into the major groove and directed toward its 5'-neighbor in the sequence. These structures provide a molecular explanation of how transient strand slippage of the lesion-containing segment can be accommodated by a double helix following translesion synthesis.

Base Sequence↗
PubMed1992

Fluorenyl fatty acids as fluorescent probes for depth-dependent analysis of artificial and natural membranes.

The main objective of depth-dependent fluorescent probes is to provide information at a distinct position in the membrane hydrophobic core. We report here a series of fluorenyl fatty acids which can probe both artificial and natural membranes at different depths. Long-chain acids (C4, C6, and C8) are attached to fluorene chromophore on one side, and a hydrophobic tail (C4) is attached on the other side, so that on incorporation in membranes the carboxyl end of the molecule is oriented toward the membrane-water interface and the hydrophobic tail points toward the membrane interior. These acids can be readily partitioned into membranes. The disposition of these fluorenyl fatty acids in membranes was studied by fluorescence quenching using iodide as a water-soluble and 9,10-dibromostearic acid as a lipid-soluble quencher. The results obtained indicate that attachment of a hydrophobic tail is essential for effective alignment of depth-dependent fluorescent probes. The length of the hydrophobic tail was varied and an n-butyl chain was found to be most effective. In all cases, the compounds with a hydrophobic tail were found to be probing the membrane deeper than their counterparts with no hydrophobic tail. Further, the compounds with hydrophobic tails were more strongly immobilized in the membrane as indicated by fluorescence polarization studies. However, the effect of such a tail varied with membrane type. Thus in artificial membranes an n-butyl chain was found to be extremely important for effective monitoring by shallow probes like 4-(2'-fluorenyl)butyric acid, whereas in erythrocyte ghost membranes the same n-butyl tail was found to be more desirable for deeper probes like 8-(2'-fluorenyl)octanoic acid.(ABSTRACT TRUNCATED AT 250 WORDS)

Erythrocyte Membrane↗
PubMed1991

Full replacement of the function of the secondary electron acceptor phylloquinone(= vitamin K1) by non-quinone carbonyl compounds in green plant photosystem I photosynthetic reaction centers.

One-carbonyl quinonoid compounds, fluorenone (fluoren-9-one), anthrone, and their derivatives are introduced into spinach photosystem (PS) I reaction centers in place of the intrinsic secondary electron acceptor phylloquinone (= vitamin K1). Anthrone and 2-nitrofluorenone fully mediated the electron-transfer reaction between the reduced primary electron acceptor chlorophyll A0- and the tertiary electron acceptor iron-sulfur centers. It is concluded that the PS I phylloquinone-binding site has a structure that enables various compounds with different molecular structures to function as the secondary acceptor and that the reactions of incorporated compounds are mainly determined by their redox properties rather than by their molecular structure. Carbonyl groups increase the binding affinity of the quinone/quinonoid compounds but do not seem to be essential to their function. The quinonoid compounds as well as quinones incorporated into the PS I phylloquinone-binding sites are estimated to function at redox potentials more negative than in organic solvents.

Anthracenes↗
PubMed1988

Design, synthesis, and fluorescence studies of fluorenyl fatty acids as new depth-dependent fluorescent probes for membranes: getting over the looping-back problem.

Fluorescent fatty acids have proved very useful in studying the membrane hydrophobic core. They readily partition into membranes or can be converted to phospholipids, which form integral components of membranes. By attaching the fluorescent chromophore to different positions along the alkyl chain of fatty acids, e.g., an anthroyloxy group attached via an ester linkage to n-hydroxystearic acid, membranes have been probed at different depths. While this is an interesting approach and has been extensively used, relatively little attention has been paid to the molecular design of these probes in order to have minimal membrane perturbation. In the present study we have looked into the general problem of design of such depth-dependent membrane probes. We report here a series of fluorenyl fatty acids with varying fatty acid chain lengths, i.e., (2-fluorenyl)acetic acid, -butyric acid, -hexanoic acid, and -octanoic acid, in order to obtain information at different depths in the membrane hydrophobic core. To see the effect of attachment of a hydrophobic tail on the orientation of such fatty acids in membranes, an n-butyl group was linked to the C-7 position of fluorene in (2-fluorenyl)butyric acid to get 4-(7-n-butylfluoren-2-yl)butyric acid. Further, to assess their ability to act as depth-dependent fluorescent probes, these fatty acids were incorporated in vesicles prepared from egg phosphatidylcholine, and their fluorescence quenching was studied with potassium iodide, Cu(II), 9,10-dibromostearic acid, and 12-bromostearic acid.(ABSTRACT TRUNCATED AT 250 WORDS)

Cell Membrane↗
PubMed2006

The FDAM method: determination of carboxyl profiles in cellulosic materials by combining group-selective fluorescence labeling with GPC.

A novel method for accurate determination of the carboxyl content in cellulosic materials by fluorescence labeling with 9H-fluoren-2-yl-diazomethane (FDAM) has been developed. The procedure can readily be implemented into a GPC system with RI and MALLS detectors, requiring additional fluorescence detection. The labeling conditions were optimized by means of sugar acid model compounds and were transferred to the cellulose case. Kinetics of the labeling and the influence of reaction parameters were comprehensively studied. For the first time, carboxyl profiles of cellulosics, i.e., the carboxyl content relative to the molecular weight distribution, were obtained.

Carboxylic Acids↗