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At least 865 records · Page 48Linked to original sources
PubMed2006

DNA damage caused by benzo(a)pyrene in MCF-7 cells is increased by verapamil, probenecid and PSC833.

The aim of this study was to clarify whether pharmaceutical drugs capable of inhibiting ABC-transporters affect the toxicity of benzo(a)pyrene (BP). MCF-7 breast adenocarcinoma cells were cultured for 24 and 48 h with benzo(a)pyrene (1 microM) and the transporter inhibitors verapamil (0.125-100 microM), PSC833 (0.05-5 microM) or probenecid (0.05-2 mM). DNA binding of benzo(a)pyrene-7,8-diol-9,10-epoxide (BPDE) was analyzed by synchronous fluorescence spectrophotometry and p53 protein by immunoblotting. BP metabolism was studied using thin layer chromatography (TLC). MTT assay and ATP quantitation were used for the analysis of cell viability. At 24 h there was no statistically significant increase in the DNA-adduct formation by any of the used inhibitors. However, at 48 h all of the inhibitors, in concentrations known to effectively block ABC transporters, increased the BPDE-DNA adduct formation 1.5 to 2-fold compared to adduct formation with BP only. PSC833 and verapamil also increased p53 protein expression at 48 h (p<0.05). Probenecid decreased glucuronidation of (3)H-BP metabolites. Other inhibitors did not decrease statistically significantly the overall formation of water-soluble metabolites. BP alone slightly decreased viability of cells at 48 h according to ATP quantitation as compared to vehicle treated controls (86.4+/-16.4%). Even though the used inhibitors showed some cytotoxicity, the combination of BP and inhibitors did not decrease cell viability in synergistic manner. According to these results certain pharmaceutical drugs may increase DNA damage caused by benzo(a)pyrene in MCF-7 cells at least partly through the inhibition of transporters. Taking into account the complex metabolism of BP and lack of specificity of the inhibitors used, it is likely that increased DNA damage seen in this study was the result of multiple interactions between the inhibitors, BP metabolism and the efflux of the compounds.

ATP Binding Cassette Transporter, Subfamily B↗
PubMed1988

Metabolism of benzo(a)pyrene by a dioxygenase enzyme system of the freshwater green alga Selenastrum capricornutum.

The green alga Selenastrum capricornutum was incubated with benzo(a)-pyrene under an atmosphere of 20% (18)O2: 80% N2. The cis-11,12-dihydro-11,12-dihydroxybenzo(a)pyrene, cis-7,8-dihydro-7,8-dihydroxybenzo(a)pyrene and cis-4,5-dihydro-4,5-dihydroxybenzo(a)pyrene, were isolated by HPLC and analyzed by mass spectrometry. The metabolites produced molecular ions at m/z 290 and 286. Elemental analysis of the ion at m/z 290 gave an elemental composition of C20H14(18)O2 with 13% (18)O2 incorporation. The results indicate that S. capricornutum produces cis vicinal dihydrodiols from molecular oxygen via a dioxygenase enzyme pathway. The dioxygenase enzymes are characteristic of the bacterial metabolic pathway and unlike those of eukaryotic organisms which involve monooxygenase enzymes.

Benzo(a)pyrene↗
PubMed1997

Monitoring the myosin ATPase reaction using a sensitive fluorescent probe: pyrene-labeled ATP.

A pyrene-labeled ATP (Pyr-ATP) in which a pyrene fluorophore is linked to the ribose moiety of ATP with a butyryl chain has been synthesized, together with the corresponding analog of ADP. The spectroscopic properties of two fluorescent analogs were found to be similar to those of 1-pyrenebutyric acid, making them photostable and highly sensitive probes for detecting changes in conformations around the nucleotide binding sites of proteins. Binding of Pyr-ADP to myosin subfragment-1 (S-1) resulted in a fluorescence quenching of about 70%. This binding was tight, with a dissociation constant (0.9 microM) similar to that of ADP itself. Formation of the stable ternary complex of Pyr-ADP with S-1 and orthovanadate could be monitored from the quench in pyrene fluorescence with a rate constant of 0.01 s-1. The final fluorescence intensity was about 20% of that for Pyr-ADP alone. Pyr-ATP was hydrolyzed by S-1 1.3 times faster than was ATP. Hydrolysis of Pyr-ATP was accompanied by an initial quenching of pyrene fluorescence with a subsequent recovery of the fluorescence. The fluorescence changes could be used to monitor the hydrolysis reaction continuously and measure the turnover rates of the analog. The fluorescence assay was sensitive, particularly under single turnover conditions, allowing hydrolysis reactions to be monitored at concentrations of S-1 and the analog as low as 50 nM.

Adenosine Diphosphate↗
PubMed2003

Characterization of the solvation environment provided by dilute aqueous solutions of novel siloxane polysoaps using the fluorescence probe pyrene.

Solubilization environment afforded by several of the novel allyl glycidyl ether-modified methylhydrosiloxane polymers are investigated using a common polycyclic aromatic hydrocarbon fluorescence probe, pyrene. The backbone of the polymer has been modified by the addition of an alkyl chain of varying length (either C8, C12, or C18) and to differing degrees of substitution. The nomenclature adopted for the purposes of these studies is as follows: "AGENT" represents the backbone polymer with no alkyl substitution, and "OAGENT", "DAGENT", and "SAGENT" are substituted with n-octyl, n-dodecyl, and n-octadecyl, respectively. The percentage of alkyl substitution is designated as 10, 15, and 20%. The pyrene polarity scale (defined as the ratio of the intensity of peak I to peak III) was used to determine the relative dipolarity of the cybotactic region provided by approximately 1 w/w% aqueous polymer solutions compared to 10 mM sodium dodecylsulfate (SDS) micellar solution. Results indicate that 10-15% DAGENT afforded the most hydrophobic solubilization site, followed by 15% OAGENT and 15% SAGENT. In addition, as the degree of alkyl substitution of DAGENT increased from 10 to 20%, the cybotactic region appeared to become more hydrophobic. Furthermore, a deeper investigation into the relative size of the solubilization site revealed that all alkyl-substituted polymers promoted excimer formation at relatively low pyrene concentrations, indicating the possibility of localized concentration enhancement within the solvation pockets and/or compartmentalization of the solute molecules. The pyrene fluorescence excitation data strongly indicates ground-state heterogeneity that is most prominent in AGENT and decreases as the alkyl chain length is increased. This provides a relative sense of the size and shape of the solvation pockets afforded by each polymer solution. An overall analysis of the collected data indicated that these alkyl-substituted polymers may provide a more selective and efficient pseudostationary phase in electrokinetic chromatography with better solvation capacity for hydrophobic compounds compared to SDS.

Chromatography, Micellar Electrokinetic Capillary↗
PubMed2001

Trans- and cis-DNA adduct concentration in epidermis from mouse and rat skin treated ex vivo with benzo[a]pyrene diol epoxide and its corresponding chlorohydrin.

Benzo[a]pyrene diol epoxide, a metabolite of benzo[a]pyrene (BaP), and chlorohydrin, the reaction product of chloride and the epoxide, form in vitro the same trans- and cis-stereoisomeric DNA adducts, but in different proportions. In this study, we asked whether the DNA adduct concentration can be kept the same by applying the appropriate dose of (+/-)-7r,8t-dihydroxy-9t,10t-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (anti-BPDE)and (+/-)-7r,8t,9t-trihydroxy-10c-chloro-7,8,9,10-tetrahydrobenzo[a]pyrene (trans-BPDCH) to rodent skin and whether the DNA adducts formed differ only in their trans- and cis-stereoisomerism. Skin from C57Bl6 mice, spontaneous hypertension rats (SHR) and Sprague-Dawley (SD) rats was treated ex vivo immediately after the death of the animals with anti-BPDE and its corresponding bay region chlorohydrin trans-BPDCH and the epidermis was analyzed for DNA adducts 1h after the application. We found that adduct formation at the exocyclic amino groups of deoxyguanosine and deoxyadenosine in epidermal DNA followed a linear dose-response within 6--100 nmol/cm(2) with both chemicals. In order to achieve the same adduct concentration in mouse, spontaneous hypertension rat (SHR), and Sprague-Dawley (SD) rat skin, respectively, a 37-, 23- and 10-fold lower dose of anti-BPDE than of trans-BPDCH had to be applied. The order of 2'-deoxyguanosine (dGuo) adduct concentration with anti-BPDE was similar to what has been reported, but the order with trans-BPDCH was (+)-cis-BPDE-N(2)-dGuo adduct>(+)-trans-BPDE-N(2)-dGuo=(-)-trans-BPDE-N(2)-dGuo>(-)-cis-BPDE-N(2)-dGuo in mouse skin. Irrespective of species or strain, a significantly higher proportion of cis-adducts was obtained after treatment with trans-BPDCH than after treatment with anti-BPDE. Therefore, DNA adduct concentration can be kept the same by applying the appropriate dose of anti-BPDE and trans-BPDCH to rodent skin and the DNA adducts formed differ only in their trans- and cis-stereoisomerism.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed2001

Fate of pyrene in contaminated soil amended with alternate electron acceptors.

Creosote-contaminated soil samples from the Libby Ground Water Contamination Superfund Site in Libby, MT, were amended with the potential alternate electron acceptors (AEA) nitrate (KNO3), manganese oxide (MnO2), and amorphous iron oxyhydroxide (FeOOH) and incubated at low oxygen tensions (0-6% O2). The fate of 14C-pyrene was evaluated with respect to the different soil amendments. The fate of 14C from the radiolabeled pyrene with regard to mineralization and bound residue formation within soil humic fractions was not significantly different from controls for the iron and manganese amended soils. Nitrate amendments appeared to stimulate 14C-pyrene mineralization at a level of 170 mg NO3-N kg(-1), and inhibit mineralization at 340 mg NO3-N kg(-1). The stimulatory effect did not appear to be the result of nitrate serving as an electron acceptor. Although AEA amendments did not significantly affect the rate or extent of 14C-pyrene mineralization, results of oxygen-deprived incubations (purged with N2) indicate that AEA may be utilized by the microbial community in the unsaturated contaminated soil system.

Biodegradation, Environmental↗
PubMed2001

Liquid chromatography study of pyrene degradation by two micromycetes in a freshwater sediment.

Pyrene biodegradation in a freshwater sediment without fungi supply, or inoculated with two sediment micromycetes, Mucor racemosus var. sphaerosporus and Phialophora alba was studied after 0, 5, 13, 28, 60 and 90 days. The influence of glucose addition was estimated, and a liquid chromatographic method for simultaneous quantitative determination of residual anthracene, fluoranthene and pyrene in the sediment was developed. Samples with PAHs were extracted in Soxhlet with ethyl acetate, and LC analysis was performed on a 5 microm Supelcosil column (150 x 4.6 mm I.D.) with gradient elution (2 ml min(-1)) of acetonitrile-water and UV detection at 254 nm. Recoveries of anthracene, fluoranthene and pyrene were 90.3%+/-1.1%, 93.2%+/-0.9% and 90.42%+/-1.9%, respectively, without interference. The native sediment microorganisms (with or without glucose added) have shown 35% pyrene degradation and sediment with glucose inoculated by the strains revealed 40%.

Biodegradation, Environmental↗
PubMed2000

Biodegradation of pyrene by sediment fungi.

Micromycetes were isolated from PAHS-contaminated sediment and identified. They were investigated for pyrene degradation (10 mg l-1) in liquid synthetic medium for two days. Among the 41 strains isolated, 10 highly degraded pyrene (> 2.4 mg g-1 dry weight): two Zygomycetes (Mucor racemosus, M. racemosus var. sphaerosporus), 6 Deuteromycetes (Gliocladium virens, Penicillium simplicissimum, P. janthinellum, Phialophora alba, P. hoffmannii, Trichoderma harzianum), a Dematiaceae (Scopulariopsis brumptii) and a Sphaeropsidale (Coniothyrium fuckelii). Zygomycetes appeared as one of the most efficient taxonomic groups, especially with Mucor racemosus. Penicillium crustosum was the only strain that did not degrade pyrene. Among the 10 fungi which were performant for pyrene degradation, nine were not yet reported in the literature and showed a real value for PAH remediation.

Aspergillus↗
PubMed2000

Effects of metabolites of benzo(a)pyrene on unschedule DNA synthesis in BALB/3T3 cell line.

In order to explore the damage from metabolites of benzo(a)pyrene on DNA of mammalian cells, the effects of four metabolites of benzo(a)pyrene (anti-BPDE, syn-BPDE, 3-OH-BP and 9-OH-BP) on synthesis of DNA and unschedule DNA synthesis (UDS) in BALB/3T3 cells were assayed, by methods of single-labeling and double-labeling. The results showed that all of the four agents were able to increase the synthesis of DNA, but only three of them (apart from syn-BPDE) induced UDS in BALB/3T3 cells. The above indicates that the metabolites of benzo(a)pyrene are able to damage DNA in BALB/3T3 cells, and that this effect may be relative to the sterical structure of metabolites of benzo(a)pyrene.

3T3 Cells↗
PubMed2000

Fluorescence imaging of pyrene-labeled lipids in living cells.

Microscopic imaging of fluorescent lipid derivatives is a powerful tool to study membrane organization and lipid trafficking but it is complicated by cellular autofluorescence background and photobleaching of the fluorophore as well as by the difficulty to selectively image membranes stacked on top of each other. Here we describe protocols that strongly alleviate such problems when pyrene-labeled lipids are being used. First, photobleaching of these lipids is virtually eliminated when oxygen is depleted from the medium by using a gentle and simple enzymatic method. Second, an image practically free of cellular autofluorescence contribution can be obtained simply by subtracting from the pyrene image the background image obtained at a slightly different excitation wavelength. This type of background subtraction more properly accounts for the typically uneven distribution of cellular background fluorescence than other, commonly used methods. Third, it is possible to selectively image the pyrene lipids in the plasma membrane by using plasma membrane-specific quencher trinitrophenyl lysophosphatidylethanolamine and image subtraction. Importantly, either the outer or the inner leaflet can be selectively imaged by labeling the cells with pyrene phosphatidylcholine or phosphatidylserine, respectively. These protocols should be of considerable help when studying organization of the plasma membrane or intracellular lipid trafficking.

Cell Membrane↗
PubMed1998

Determination of albumin adducts of (+)-anti-benzo[a]pyrene-diol-epoxide using an high-performance liquid chromatographic column switching technique for sample preparation and gas chromatography-mass spectrometry for the final detection.

A novel method has been developed for the determination of (+)-anti-benzo[a]pyrene-diol-epoxide [(+)-anti-BPDE] albumin adducts in the low-picogram range. Blood from rats and humans was investigated for the validation of the method. Instead of the usual acid hydrolysis we used alkaline conditions for the cleavage of the esters formed with asparagic or glutamic acid residues of albumin. Alkaline hydrolysis gave rise to benzo[a]pyrene-r-7,t-8,t-9,c-10-tetrahydrotetrol (BT I-1) which was separated from the matrix by HPLC with a column switching technique. The analytes were collected by an automated fraction collector and after silylation determined with GC-MS using negative chemical ionization. Adduct concentrations were calculated by the internal standard method. Benzo[a]pyrene-r-7,t-8,c-9,c-10-tetrahydrotetrol (BT-II-2) was used as an internal standard because of its similar physicochemical properties and its absence from human samples. To determine the recovery of the analytical procedure benzo[a]pyrene-r-7,t-8,t-9,t-10-tetrahydrotetrol (BT I-2) was added at the end of the sample clean-up. Single ion recording mode was applied for the detection of the analyte and the standards using the abundant fragment ion m/z 284 for quantitation of the three tetrols. The mean recovery of the internal standard BT II-2 was about 50%. The limit of detection was 0.15 pg per injection corresponding to 0.01 fmol/mg albumin. Regression coefficients of the calibration curves were r2=0.99 and r2=0.98 for BT I-1 concentration ranges of 4-400 ng/l and 4-40 ng/l, respectively. The mean coefficient of variation for duplicate analyses of human albumin samples was found to be 22%.

Animals↗
PubMed2003

Spontaneous and benzo[a]pyrene-induced micronuclei in the embryos of the black-headed gull (Larus ridibundus L.).

The spontaneous levels of micronuclei in erythrocytes were established in embryos of the black-headed gull of two natural populations. In total 216 blood samples from the same number of individuals were examined. A statistically significant decrease in the number of spontaneous micronucleated erythrocytes was found after 13 days of incubation. We found no statistically significant difference in the spontaneous frequencies of micronucleated erythrocytes in the embryos of the two colonies studied, although they differed in anthropogenic load. Results of analysis of variance indicated that egg incubation time was the only variable significantly (P=0.0001) affecting spontaneous frequency of micronucleated erythrocytes in the embryos of black-headed gulls. We also took 78 eggs of different developmental stages from both colonies and exposed them for a further 24h to a dose of benzo[a]pyrene (30 microg per egg). After exposure to benzo[a]pyrene, the frequency of micronucleated erythrocytes was not increased in the embryos incubated for a total period of 13 days. A statistically significant increase in the number of micronucleated erythrocytes was recorded in the benzo[a]pyrene-treated embryos incubated for a total period of 14 days. Decrease in numbers of spontaneous micronucleated erythrocytes after the 13 day of incubation and increased levels of benzo[a]pyrene-induced micronuclei after the 13 day of incubation were discussed to be caused by changes in spleen and liver function in advanced developmental stages of the embryo.

Animals↗
PubMedDate not supplied

Synthesis and properties of an oligodeoxynucleotide modified with a pyrene derivative at the 5'-phosphate.

The synthesis of an oligonucleotide (ODN) modified with pyrene (pyr) on the 5'-phosphate is described. The ODN and pyrene are joined through a linker composed of four methylene groups. Modification of the oligonucleotide was effected via condensation of the 2-cyanoethyl N,N-diisopropylphosphoramidite of 4-(1-pyrenyl)butanol (pyr-m4OPAm, 2) with the 5'-OH of an ODN. This derivative is suitable for incorporation into automated solid-phase DNA synthesis and was attached to the 5' terminus of the DNA chain through a phosphodiester linkage. The properties of the 5'-(pyr-m4)d(T)15 (3) and the duplex it formed with d(A)15 were investigated by fluorescence and absorbance spectroscopy. The pyrene fluorescence in the modified duplex was quenched 96.3% relative to an identical concentration of free 4-(1-pyrenyl)butanol. The ultraviolet spectrum of the 5'-(pyr-m4)-d(T)15 and 5'-(pyr-m4)-d(T)15-d-(A)15 modified duplex, in the 320-360-nm region, was red-shifted 6 nm relative to the free 4-(1-pyrenyl)-butanol. The Tm values of the unmodified and modified duplexes at 0.1 M NaCl were 34.9 and 41.9 degrees C, respectively. The pyrene-induced stabilization corresponds to a free energy change (delta delta G degrees) of -2.6 kcal/mol.

Oligonucleotides↗
PubMedDate not supplied

Biotin-pyrene conjugates with poly(ethylene glycol) spacers are convenient fluorescent probes for avidin and streptavidin.

Conventional biotin-fluorophore conjugates with approximately 14 atom spacers are strongly quenched when bound to avidin or streptavidin, whereas fluorescence becomes insensitive to receptor binding if typical fluorophores are linked to biotin via poly(ethylene glycol) (PEG) chains (Gruber et al., see the second of three papers in this issue). In the present study the antagonism between PEG-PEG repulsion and fluorophore interaction was examined more closely, using biotin-PEG-pyrene conjugates as model compounds. The antagonistic tendencies between hydrophilic PEG chains and hydrophobic pyrene labels were about balanced in the PEG1900 derivative since quenching was approximately 50% in 4:1 complexes with avidin or streptavidin. In contrast, strong quenching and concomitant excimer fluorescence was seen with the biotin-PEG800-pyrene conjugate, providing for a new fluorescence assay to accurately measure avidin and streptavidin concentrations at > or = 40 and > or = 10 nM, respectively. Association/ dissociation kinetics were analyzed from pyrene fluorescence changes, and dissociation constants were deduced. About 3-fold affinities were observed for streptavidin as compared to avidin, and little influence of PEG chain length was seen. All affinities were increased by a factor of approximately 3 when biotin-PEG-tetramethylrhodamine conjugates were used. The observed effect of fluorophore variation upon biotin binding is unexpectedly small; thus, the kinetic/thermodynamic data appear to be representative for biotin-PEG conjugates in general.

Avidin↗
PubMed1985

Interactions of pyrene derivatives with lipid bilayers and with (Ca2+-Mg2+)-ATPase.

The intensities of fluorescence emission for pyrene and a number of its derivatives increase on binding to lipid bilayers and to the (Ca2+-Mg2+)-ATPase purified from rabbit muscle sarcoplasmic reticulum. The effect is particularly marked for the less water-soluble derivatives. Changes in intensity for monomer and excimer emission as a function of lipid concentration can be fitted to a simple model to obtain binding parameters. The number of binding sites per lipid is 0.2-0.4. For the ATPase system, at least two classes of sites are necessary to fit the data, one corresponding to the lipid component and one to sites on the ATPase. Excimer emission from the postulated sites on the ATPase is less marked than that from lipid. Pyrene-dodecanoic acid and pyreneundecyltrimethylammonium bromide, which bind to a large number of sites on the ATPase, cause marked inhibition of ATPase activity at high concentration. Pyrene and a number of water-soluble derivatives cause stimulation of the ATPase reconstituted with dimyristoleoylphosphatidylcholine and little inhibition and bind to a small number of sites on the ATPase. It is concluded that excimer emission from pyrene derivatives in systems containing proteins cannot be used to obtain reliable information about rates of diffusion in the lipid component of the membrane.

Animals↗
PubMed1990

Pyrene eximer mapping in cultured fibroblasts by ratio imaging and time-resolved microscopy.

The kinetics of pyrene eximer formation provide a measure of lateral diffusibility in bilayer membranes. Swiss 3T3 fibroblasts were labeled with pyrene, pyrenedecanoic acid (PDA) and 1,3-bis(1 pyrene) propane (BPP) by incubation in the presence of Pluronic F127. Single-cell emission spectra obtained by epifluorescence microscopy (excitation 350 nm) with photodiode array detection showed monomer (380-420 nm) and eximer (475 nm) peaks. The eximer-to-monomer fluorescence ratio (E/M) increased with increasing temperature and loading time. Time-resolved microscopy studies of fibroblasts labeled with PDA for 15 min gave monomer and eximer lifetimes of 101 and 78 ns, respectively, with a monomer-to-eximer conversion rate of 0.02 ns-1. E/M ratio images were obtained with a microchannel plate intensifier and CCD camera at 350-nm excitation and 405 +/- 5 nm (monomer) and greater than 470-nm (eximer) emission wavelengths. E/M ratios of PDA showed spatial variation across the cell with highest ratios at the peripheral plasma membrane. These results establish the methodology to label cells with pyrene eximer-forming probes and to image eximer distributions in membranes of intact cultured cells. Eximer-to-monomer fluorescence ratios are sensitive to maneuvers that alter the membrane physical state and should be of utility in examining the cellular regulation of membrane fluidity.

Animals↗
PubMed1997

Triple helix formation and homologous strand exchange in pyrene-labeled oligonucleotides.

The orientations of the symmetrical third strands (G3A4G3) and (G3T4G3) within the triplexes (C3T4C3) - (G3A4G3) x (G3A4G3) and (C3T4C3) - (G3A4G3) x (G3T4G3) were investigated by fluorescence spectroscopy and thermal denaturation using pyrene-labeled oligodeoxynucleotides. In the two triplex structures, both parallel and antiparallel orientations of the third strand with respects to the purine Watson-Crick one were identified by means of pyrene excimer formation. The pyrene labels do not modify the melting temperature of the (C3T4C3) - (G3A4G3) x (G3T4G3) triplex but somewhat stabilize the corresponding duplex against thermal denaturation. The absorption melting profiles of the (C3T4C3) - (G3A4G3) x (G3A4G3) triplex are monophasic in agreement with previous reports. In contrast, the melting of this structure, when monitored by the pyrene excimer band, reveals a biphasic behavior. These data, together with kinetics measurements, strongly suggest exchange mechanisms between the homologous oligomers (G3A4G3), Hoogsteen, and Watson-Crick strands.

DNA↗
PubMed2005

Conformational changes of pyrene-labeled polyelectrolytes with pH: effect of hydrophobic modifications.

Structural changes of pyrene-labeled and unlabeled poly(maleic acid/octyl vinyl ether) (PMAOVE) and poly(maleic acid/methyl vinyl ether) (PMAMVE) with changes in pH have been investigated in this study. The changes in the photophysical properties of pyrene are interpreted to investigate uncoiling or swelling of the polymeric chains with pH. The vibrational fine structure of the pyrene fluorescence (I(3)/I(1)) and the ratio between excimer and monomer fluorescence (I(e)/I(m)) of both pyrene-labeled and unlabeled PMAMVE and PMAOVE suggest that, at pH 4, the polymers are in the coiled form and PMAOVE forms hydrophobic nanodomains. An increase in pH ionizes a number of COOH groups on both PMAMVE and PMAOVE, which leads to the stretching or swelling of the polymers.

Hydrogen-Ion Concentration↗