Clear and simple detection of asbestos stained with two dyes for building materials collected from disaster and demolition sites using a stereomicroscope.

Whenever houses are demolished or disasters occur, large quantities of building materials are discharged, which may contain asbestos. To prevent the damage caused by asbestos exposure, a rapid asbestos presence confirmation method is required at demolition sites or temporary disaster storage sites. It is difficult to confirm the presence of asbestos in waste building materials by simple observation. However, it can be confirmed by staining the materials with two dyes: methylene blue (MB) with positive charge, and erythrosine (RED-3) with negative charge, and using a stereomicroscope. The method was applied to samples collected from disaster and demolition sites. Asbestos was stained violet or reddish-purple, and the base material of the building materials remained blue. Using this method, even amateur workers can detect asbestos by means of an image in a different color than the building substrate. Furthermore, the present method detected asbestos more explicitly than the official method (JIS A 1482, 1483; detection limit is < 0.1%) recommended by the Japanese government. This cost-effective method is suitable for detecting asbestos at disaster and demolition sites. The mixture of MB and RED-3 formed nanoparticles of size 151 nm and surface charge of -34 mV that selectively stained asbestos. The staining mechanism was discussed.

On-site detection of asbestos at the surface of building materials wasted at disaster sites by staining.

We have developed a method to detect asbestos by staining the surface of building materials in order to quickly detect asbestos-containing building materials at disaster sites. After staining, asbestos was easily detected by the color and characteristic shape of the images observed under a stereomicroscope. The type of asbestos was confirmed to be chrysotile by polarized light microscopy, X-ray diffraction patterns, and Raman spectra. The percentage of the area of asbestos at the surface of building materials was also determined by an image analyzer after the dye staining, and the distribution percentage of asbestos increased with its total concentration in the building material. Three-dimensional X-ray computed tomography images showed that asbestos was mainly distributed at the surface of building materials. This result suggests that the asbestos at the surface of debris of building materials is more easily and sensitively detected than total asbestos analysis by pulverization. The present method was applied to detect and determine asbestos in debris of building materials wasted at temporary storage sites after disaster and on the wall of a building in use. Therefore, this method can contribute to the classification of asbestos-containing and non-asbestos-containing building materials at disaster sites and demolition sites, as well as to preliminary inspections for the detection of asbestos-containing building materials before demolition of houses and buildings.

Kinetics and mechanism of formation of nickel(II)porphyrin and its interaction with DNA in aqueous medium.

Kinetics between 5,10,15,20-tetrakis(N-methylpyridium-4-yl)porphyrin and Ni2+ species were investigated in aqueous solution at 25 ±1 °C in I = 0.10 M (NaNO3). Speciation of Ni2+ was done in I = 0.10 M (NaNO3) for knowing distribution of Ni2+ species with solution pH. Experimental data were compared with speciation diagram constructed from the values of hydrolysis constants of Ni2+ ion. Speciation data showed that hexaaquanickel(II) ions took place in hydrolysis reactions through formation of [Ni(OH2)6-n(OH)n]2-n species with solution pH. According to speciation of Ni2+ and pH dependent rate constants, rate expression can be written as: d[Ni(TMPyP)4+]/dt = (k 1[Ni2+ (aq)] + k 2[Ni(OH)+ (aq)] + k 3[Ni(OH)2 o (aq)] + k 4[Ni(OH)3 - (aq)])[H2TMPyP4+], where k 1, k 2, k 3 and k 4 were found to be k 1 = (0.62 ± 0.22) × 10-2; k 2 = (3.60 ± 0.40) × 10-2; k 3 = (2.09 ± 0.52) × 10-2, k 4 = (0.53 ± 0.04) × 10-2 M-1s-1 at 25 ±1 °C, respectively. Formation of hydrogen bonding between [Ni(H2O)5(OH)]+ and [H2TMPyP]4+ causes enhanced reactivity. Rate of formation of [Ni(II)TMPyP]4+ complex was to be 3.99 × 10-2 M-1s-1 in I = 0.10 M, NaNO3 (25 ± 1 °C). UV-Vis and fluorescence data suggested that [Ni(II)TMPyP]4+ and [H2(TMPyP)]4+ interact with DNA via outside binding with self-stacking and intercalation, respectively. SYNOPSIS. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s12039-021-01945-y.

Effect of emulsifiers on the discoloration of chlorophyll and their potential for use in green beverages.

The discoloration of chlorophyll (Chl) by light is an ongoing issue for green beverages in the food industry. To suppress the discoloration of Chl in aqueous solution, the effects of different emulsifiers were investigated on the discoloration of Chl under ultraviolet (UV) irradiation to determine their potential application for use as food additives. Sucrose fatty acid ester (SE), sorbitan fatty acid ester (TW), and quillaja saponin (QS) were used as emulsifiers, while Triton X-100 (TX) was used for reference. The discoloration of Chl was measured using a color difference meter. The species of Chl in solution were determined using ultraviolet-visible (UV-Vis), fluorescence, and circular dichroism (CD) spectroscopy, and the particle size of Chl in solution was determined using dynamic light scattering. The Chl aggregates were observed by the observation of increased peak areas at longer wavelengths in the UV spectra of Chl, in addition to a reduced fluorescence intensity. The CD spectra showed that the Chl aggregates were arranged in a random structure. Furthermore, the average particle size of the Chl aggregates was determined to be approximately 100 nm. SE and QS were found to significantly enhance the formation of self-aggregates due to their high hydrophilicities compared to those of TW and TX. As a result, SE and QS protect themselves from light to suppress the discoloration of Chl. The present results therefore suggest that SE and QS are suitable emulsifiers to address the problem of Chl discoloration in beverages, such as green tea and vegetable juices. PRACTICAL APPLICATION: Chlorophyll (Chl), a green pigment present in vegetables and green tea, is discolored by light. In this study, it was found that emulsifiers (sucrose fatty acid ester and quillaja saponin) suppress the discoloration of Chl. The implementation of these emulsifiers as food additives would enable green tea or green vegetable juices to maintain their colors for long periods and could contribute significantly to the beverage industry.

Physico-chemical chlorophyll-a species in aqueous alcohol solutions determine the rate of its discoloration under UV light.

Chlorophyll-a (Chl-a) discolors when it is exposed to light, and such discoloration decreases food quality. To elucidate the discoloration mechanism of Chl-a, we determined discoloration rate in different Chl-a chemical species and assessed the size of Chl-a aggregates in mixed aqueous solutions of methanol and ethanol. Chl-a existed as monomer, J-aggregate, and random aggregate in solutions with different alcohol concentrations. The predominant species depended on the alcohol concentration. Monomeric Chl-a and J-aggregates discolored quickly, whereas random aggregates discolored slowly. Particle sizes of J-aggregates were 319 and 2305 nm in diameter in aqueous solutions of methanol and ethanol, respectively. The sizes of random aggregates were 51 and 79 nm in 10% (v/v) aqueous solutions of methanol and ethanol, respectively. The size of Chl-a aggregates positively correlated with the rate of Chl-a discoloration under UV light. Based on the results obtained, we propose a mechanism of Chl-a discoloration.

Simple analysis of total mercury and methylmercury in seafood using heating vaporization atomic absorption spectrometry.

This study aimed to develop a simpler method for determining total mercury (T-Hg) and methylmercury (MeHg) in biological samples by using methyl isobutyl ketone (MIBK) in the degreasing step. The fat in the samples was extracted by MIBK to the upper phase. T-Hg transferred into the water phase. This was followed by the extraction of MeHg from the water phase using HBr, CuCl2 and toluene. The MeHg fraction was reverse-extracted into L-cysteine-sodium acetate solution from toluene. The concentrations of T-Hg and MeHg were determined by heating vaporization atomic absorption spectrometry. Certified reference materials for T-Hg and MeHg in hair and fish were accurately measured using this method. This method was then applied to determine T-Hg and MeHg concentrations in the muscle, liver and gonads of seafood for the risk assessment of MeHg exposure. The mean T-Hg and MeHg concentrations in squid eggs were 0.023 and 0.022 µg/g, and in squid nidamental glands 0.052 and 0.049 µg/g, respectively. The MeHg/T-Hg ratios in the eggs and nidamental glands of squid were 94.4% and 96.5%, respectively. The mean T-Hg and MeHg concentrations in the gonads of sea urchins were 0.043 and 0.001 µg/g, respectively, with a MeHg/T-Hg ratio of 3.5%. We developed an efficient analytical method for T-Hg and MeHg using MIBK in the degreasing step. The new information on MeHg concentration and MeHg/T-Hg ratios in the egg or nidamental glands of squid and gonads of sea urchin will also be useful for risk assessment of mercury in seafood.

Hydrodechlorination/detoxification of PCDDs, PCDFs, and co-PCBs in fly ash by using calcium polysulfide.

Dioxins like polychlorinated dibenzo-p-dioxins (PCSDDs), polychlorinated dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs) are mainly emitted from waste incinerators (WIs) and have become an international research focus because of its serious concerns over the adverse health effects. The detoxification of PCCDs/Fs and PCBs is very difficult because of their stable chemical structure. A significant hydrodechlorination/detoxification of polychlorinated 1-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs) were achieved in fly ash by using an aqueous mixture of calcium hydroxide and sulfur. Two different fly ashes were studied: originating from municipal waste incinerator (FA1) and industrial waste incinerator (FA2). They were heated with the aqueous mixture at 150°C for 30 or 60 min with agitation. Higher decomposition (87%) and detoxification (87.7%) of PCDD/Fs and PCBs were achieved at 150°C with two runs; every run was for 30 min, compared to one run for 60 min. FA2 gave higher decomposition and detoxification as compared to FA1, which might be due to higher metal content that played a catalytic role to decompose and detoxify the PCDDs, PCDFs and PCBs. The decomposition and detoxification of PCDFs in fly ash was higher than PCDDs and was augmented with increasing number of chlorides on aromatic compounds. As the highly significant decomposition and detoxification of higher concentration of PCDD/Fs and PCBs were achieved in 1 hour without additive catalyst and at low temperature of 150°C, therefore, the developed method is cost effective and most suitable to apply on commercial/industrial level. The detail results of hydrodechlorination/detoxification of PCDD, PCDFs at different conditions are described and its mechanism is discussed.

Effects of metal ions (Cu²âº, Fe²âº and Fe³âº) on HPLC analysis of catechins.

Catechins [(-)-epicatechin (EC), (-)-epigallocatechin (EGC), (-)-epicatechin gallate (ECG) and (-)-epigallocatechin gallate (EGCG)] were analysed by HPLC using an ODS column, an electrochemical detector (0.75V vs. Ag/AgCl) and an eluting solvent composed of water containing buffer (84% v/v), acetonitrile (12% v/v) and ethylacetate (4% v/v) in the presence of metal ions (Cu(2+), Fe(2+) and Fe(3+)). HPLC peaks were affected by metal ions: the peak intensities of ECG and EGCG decreased, but the peak intensities of EC and EGC were not affected seriously. Fe(2+) most markedly decreased the peak intensities of EGCG. EDTA was added to mask metal ions and an optimum condition was proposed. The effects of the metal ions on HPLC analysis are discussed from the viewpoints of metal complex formation with catechins and oxidation of catechins on the basis of ultraviolet-visible (UV-vis) spectrophotometry, electrospray ionisation mass spectrometry (ESI-MS) and cyclic voltammetry (CV).

Dechlorination/detoxification of aromatic chlorides using fly ash under mild conditions.

An efficient dechlorination/detroxification method for p-nitrochlorobenzene, p-chloroanisole and 1-chloronaphthalene on municipal waste incinerator fly ash in presence of reducing agents with water/alcohol mixtures was developed. Dechlorination% was higher in water/isopropanol mixture at temperature <100 degrees C. Metal contents of fly ash played a vital role in enhancing dechlorination at low temperature. Moreover, the fly ash particles provided the surface to accomplish reduction and substitution reactions by adsorbing the chlorinated aromatic compound, hydrogen and hydroxyl ions. The mechanism of dechlorination was envisaged.

Micro-solvent cluster extraction using aqueous mixed solvents of ionic liquid.

Organic compounds (2-naphthol, phenol, 4-chlorophenol, 4-nitrophenol, and 1,3,5-naphthalenetrisulfonic acid) were sufficiently separated from mixtures during flow in a fused silica capillary tube (50 microm in i.d. and 45 cm in length) with an aqueous mixed solvent of an ionic liquid, 1-butyl-3-methylimidazolium chloride (BMIM(+)Cl(-)), without a specific separation column. The method is based on micro-solvent cluster formation in aqueous mixed solvents of ionic liquid and preferential solvation of solvent clusters to analytes. The measurement of large angle X-ray scattering (LAXS) of aqueous mixed solvents with an ionic liquid of tetrafluoroborate (BMIM(+)BF(4)(-)) indicated the formation of micro-solvent clusters of water and ionic liquid in the mixed solvent. A neutral polymer (polyvinylpyrrolidone, PVP) enhanced the separation. Polarized or ionic molecules eluted slowly. The theoretical plate numbers were 6320, 22907, 63645, and 37184 for 2-naphthol, phenol, 4-chlorophenol, and 4-nitrophenol, respectively, under the conditions of 1.0 M of BMIM(+)Cl(-) and 0.1 M of PVP; the flow rate was 1 microL min(-1). The separation mechanism is discussed from the viewpoint of the partition of analytes between micro-solvent clusters of water and organic solvent molecules.

Extraction of chromium(VI) by salting-out with a homogeneous, mixed solvent of water and 2-propanol: a laboratory study.

BACKGROUND, AIMS AND SCOPE: Chromium enters into the aquatic environment as a result of effluent discharge from steel works, electroplating, leather tanning industries and chemical industries. As the Cr(VI) is very harmful to living organisms, it should be quickly removed from the environment when it happens to be contaminated. Therefore, the aim of this laboratory research was to develop a rapid, simple and adaptable solvent extraction system to quantitatively remove Cr(VI) from polluted waters. METHODS: Aqueous salt-solutions containing Cr(VI) as CrO4(2-) at ppm level (4-6 ppm) were prepared. Equal volumes (5 ml) of aqueous and organic (2-PrOH) phases were mixed in a 10 ml centrifuge tube for 15 min, centrifuged and separated. Concentrations of Cr(VI), in both the aqueous and organic phases, were determined by atomic absorption spectrometry. The effects of salt and acid concentrations, and phase-contact time on the extraction of Cr(VI) were investigated. In addition, the extraction of Cr(VI) was assessed in the presence of tetramethylammonium chloride (TMAC) in 2-PrOH phase. Effects of some other metals, (Cd(II), Co(II), Cu(II), Ni(II) and Zn(II)), on the extraction of Cr(VI) were also investigated. RESULTS AND DISCUSSION: The Cr(VI) at ppm level was extracted quantitatively by salting-out the homogeneous system of water and 2-propanol(2-PrOH) using chloride salts, namely CaCl2 or NaCl, under acidic chloride media. The extracted chemical species of Cr(VI) was confirmed to be the CrO3Cl-. The ion-pair complex extracted into the organic phase was rationalized as the solvated ion-pair complex of [2-PrOH2+, CrO3Cl-]. The complex was no longer stable. It implied the reaction between extracted species. Studies revealed that salts and acid directly participated in the formation of the above complex. Use of extracting agents (TMAC) didn't show any significant effect on the extraction of Cr(VI) under high salting-out conditions. There is no significant interference effect on the extraction of Cr(VI) by the presence of other metals. The Cr(VI) in the organic phase was back-extracted using an aqueous ammonia solution (1.6 mol dm(-3)) containing 3 mol dm(-3) NaCl. The extraction mechanism of Cr(VI) is also discussed. CONCLUSIONS: Salting-out of homogeneous mixed solvent of 2-propanol can be employed to extract Cr(VI) quantitatively, as an ion-pair of [2-PrOH2+ * CrO3Cl-] solvated by 2-PrOH molecules. Then, the complex becomes 'solvent-like' and is readily separated into the organic phase. The increase of Cl- ion concentration in the aqueous phase favors the extraction. The 2-PrOH, salts and acid play important roles in the extraction process. There is no need to use an extracting agent at a high salting-out condition. RECOMMENDATIONS AND PERSPECTIVES: Chromium(VI) must be quickly removed before it enters into the natural cycle. As the 2-PrOH is water-miscible in any proportion, ion-pairing between 2-PrOH2+ and CrO3Cl- becomes very fast. As a result, Cr(VI) can easily be extracted. Therefore, the method is recommended as a simple, rapid and adaptable method to quickly separate Cr(VI) from aqueous samples.

An attempt to discriminate between the hydrophobic and aromatic pi-pi interactions in the copper(II) ternary complexes CuLA with L=1,10-phenanthroline or 2,2'-bipyridyl and A=para-X-substituted phenylalaninates.

For the title complexes, the value of formation constant K(CuL+A) is higher than that of K1(CuA2). According to the mechanistic consideration, log K(CuL+A) is calculated for regular Cu(II) complexes with neither special enhancement nor diminution of the stability constant. Then, the difference of log K(CuL+A)(obs)-log K(CuL+)(calc) represents extrastabilization due to the hydrophobic interactions and the aromatic pi-pi interactions. The former has been found to be proportional to the free energy of the transfer of side chains of aminocarboxylates A. The discrimination between the hydrophobic and the aromatic pi-pi interactions has been attempted.

Electrochemical behaviors of sulfhydryl compounds in the presence of elemental mercury.

In the expression of bioaccumulated elemental mercury (Hg 0) toxicity, the first Hg 0 oxidation step is crucial. Therefore, to clarify the mechanism underlying the interactions of sulfhydryl (SH) compounds and Hg 0 in the present study, we analyzed the oxidation of reduced glutathione (GSH) and L-cysteine (Cys) in the presence of Hg 0 in aqueous solution by cyclic voltammetry (CV). Production of Hg2+ in the reaction mixture was found to increase along with a decrease in free SH residues. CV showed that the oxidation of Cys increased after a 4-h incubation in the presence of Hg(0), but the oxidation of Cys after a 24-h incubation was suppressed. Conversely, GSH oxidation increased with incubation time in the absence of Hg(0). In the presence of Hg(0), the oxidation of GSH was suppressed. The different reactivities of Cys and GSH with Hg(0) may arise from differences in their oxidation/reduction potentials and pH. The important SH compound interactions with Hg(0) oxidation were as follows: (i) oxidation of Hg(0) to form either mercurous ion (Hg+) or mercuric ion (Hg2+) which both form stable complexes in aqueous solution as Hg I (RS) or Hg II(RS)2; (ii) catalyzed oxidation of SH compounds in the presence of Hg 0; and (iii) suppression of the oxidation of SH compounds due to the reduced concentration of free SH compounds through the binding of SH compounds with Hg+ or Hg2+ The present results demonstrate the chemical reaction processes by which Hg 0 dissolves in aqueous solution in the presence of SH compounds, and contribute to our understanding of SH compounds in non-enzymatic Hg 0 oxidation in vivo.

Electrochemical behaviors of native and thermally denatured fish DNA in the presence of cytosine derivatives and porphyrin by cyclic voltammetry using boron-doped diamond electrode.

The electrochemical behaviors of native and thermally denatured fish DNA was investigated using boron-doped diamond (BDD) film electrode by cyclic voltammetry. The BDD electrode afforded us to measure weak current less than muA for the DNA solution in 100 microl. The mixture of acetic acid and sodium acetate solution (0.2 M) was used as a supporting electrolyte. Two oxidation peaks were observed at about +1.1 V and +1.3 V at pH 4.6 for thermally denatured fish DNA. This is due to the oxidation of guanine and adenine in the denatured fish DNA, respectively. In contrast, the native fish DNA showed ill-defined peaks at +1.1 V. Furthermore, the electrochemical behaviors of thermally denatured fish DNA were studied in the presence of cytosine, cytidine, cytidine-5-monophosphate, tetrakis(1-methypyridinium-4-yl)porphyrin (H(2)(TMPyP)(4+)) and Ru(II)(TMPyP)(4+). The oxidation peak intensity at +1.1 V gradually decreased with the increase of the concentrations of the above compounds. Based on the above studies, electrochemical behaviors of the thermally denatured fish DNA at BDD electrode is discussed.

Spectrophotometric titration of cobalt(II) with CaCl2 in mixed solvents of 2-propanol and water for the analysis of the extraction mechanism of cobalt(II) by salting-out in the presence of CaCl2.

The spectrophotometric titration of cobalt(II) with CaCl2 was carried out in mixed solvents of 2-propanol and water at different solvent compositions of 2-propannol, water and CaCl2 to analyze the salting-out extraction mechanism of Co(II) by the addition of CaCl2 from the mixed solvents. The formation constants of betaCoCl4(2-) = [CoCl4(2-)][Co2+](-1)[Cl-](-4) in both the organic and aqueous phases were determined thorough non-linear regression of the spectrophotometric titration data by a computer program SPECFIT/32. The values of log betaCoCl4(2-) in the aqueous phases were -4.26 +/- 0.03, -4.03 +/- 0.07, -3.83 +/- 0.04, -3.69 +/- 0.03 and -3.46 +/- 0.01 at mole fractions of 2-propanol of 0.026, 0.023, 0.017, 0.014 and 0.012, respectively, and at [CaCl2]/mol dm(-3) values of 3.555 (I = 10.6), 4.276 (I = 12.8), 4.916 (I = 14.7) and 5.444 (I = 16.3), respectively. The formation constants of [CoCl4(2-)] in the organic phase were 5.70 +/- 0.06, 5.44 +/- 0.03, 5.36 +/- 0.06, 5.10 +/- 0.04 and 4.84 +/- 0.05 at mole fractions of water of 0.431, 0.441, 0.444, 0.447 and 0.451, respectively, and at [CaCl2]/mol dm(-3) of 0.941 (I = 2.8), 0.943 (I = 2.8), 1.013 (I = 3.0), 1.090 (I = 3.3) and 1.165 (I = 3.5), respectively. These results suggest the formation of [CoCl4(2-)] of 23-90% in the aqueous phase at the above mole fractions and the quantitative formation of [CoCl4(2-)] in the organic phase. The extraction percentage of [CoCl4(2-)] increased with an increase in [CaCl2]. The distribution constant, KD (= [CoCl4(2-)]org/[CoCl4(2-)]aq), however, decreased and became constant with [CaCl2]. The detailed extraction mechanism of Co(II) is discussed.

Toluene/ter-butanol mixed solvent for the selective extraction of Cr(VI) from divalent heavy metals.

A solvent-extraction system comprising toluene/ter-butanol (ter-BuOH) mixed solvent as the organic phase was developed to selectively extract Cr(VI) from acidic chloride media in the presence of divalent metals, namely Cd(II), Co(II), Cu(II), Ni(II) and Zn(II) under 5 M CaCl2 salting-out conditions. Chromium(VI) was selectively extracted as a solvated ion-pair of [ter-BuOH2+ x CrO3Cl-] at ter-BuOH mole fractions of between 0.1 and 0.6 (9.0-57.2% in volume). Divalent metals were extracted at ter-BuOH mole fraction over 0.6 with extraction percents of Co (< 20%), Cu (< 15%), Ni (< 10%) and Zn (< 20%). The concentrations of Ca2+, water and ter-BuOH in the organic phase and ter-BuOH in the aqueous phase were determined to find out the effects on the extraction of Cr(VI). The chemical species of Cr(VI) in acidic chloride media containing 5 M CaCl2 and 0.1 M HCl was confirmed to be the CrO3Cl- species. The effects of the acid, salt concentrations in the aqueous phase and the solvent composition of a mixed organic solvent on the extraction of Cr(VI) were evaluated. Based on the above studies, the extraction mechanism was elucidated and the optimum extraction conditions were determined.

Oxidative DNA damage induced by HEPES (2-[4-(2-hydroxyethyl)-1-piperazinyl]ethanesulfonic acid) buffer in the presence of Au(III).

Oxidative DNA damage was investigated by free radicals generated from HEPES (2-[4-(2-hydroxyethyl)-1-piperazinyl]ethanesulfonic acid) buffer, which is widely used in biochemical or biological studies, in the presence of Au(III). The effect of free radicals on the DNA damage was ascertained by gel electrophoresis, electron spin resonance (ESR) spectroscopy and circular dichroism (CD) spectroscopy. ESR results indicated the generation of nitrogen-centered cationic free radicals from the HEPES in the presence of Au(III) which cause the DNA damage. No ESR spectra were observed for phosphate, tris(hydroxymethyl)aminomethane (Tris-HCl) and acetate buffers in the presence of Au(III) or for HEPES buffer in the presence of other metal ions such as Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and Pd(II) or [Au(III)(TMPyP)](5+) and [Pd(II)(TMPyP)](4+), where [H(2)(TMPyP)](4+) denotes tetrakis(1-methylpyridium-4-yl)porphyrin. Consequently, no DNA damage was observed for these buffer agents (e.g., phosphate, Tris-HCl or acetate) in the presence of Au(III) or for HEPES in the presence of other metal ions or the metalloporphyrins mentioned above. No detectable inhibitory effect on the DNA damage was observed by using the typical scavengers of reactive oxygen species (ROS) ()OH, O(2)(-) and H(2)O(2). This non-inhibitory effect indicated that no reactive oxygen species were generated during the incubation of DNA with HEPES and Au(III). The drastic change in CD spectra from positive ellipticity to negative ellipticity approximately at 270 nm with increasing concentration of Au(III) also indicated the significant damage of DNA. Only HEPES or Au(III) itself did not damage DNA. A mechanism for the damaging of DNA is proposed.

In vitro toxicity of palladium(II) and gold(III) porphyrins and their aqueous metal ion counterparts on Trypanosoma brucei brucei growth.

The trypanocidal effects of aqueous gold(III) and palladium(II) and their metalloporphyrin derivatives on Trypanosoma brucei brucei growth in culture have been studied using an Alamar Blue indicator assay. All the experiments were conducted in the dark. As previously described for mercury(II), cadmium(II) and lead(II) porphyrins [Chem.-Biol. Interact. 139 (2002) 177], the toxicity of the metalloporphyrin complex of palladium(II) to T. b. brucei parasites was much higher compared to the aqueous free palladium(II) and free base porphyrin. Palladium(II) porphyrin, free palladium(II), and the free base porphyrin were trypanocidal to T. b. brucei at concentrations >1.5 x 10(-6), >6.1 x 10(-6) and >1.9 x 10(-5) M, respectively. While gold(III) porphyrin was effective against the parasites at concentrations >4.8 x 10(-6) M, its aqueous gold(III) was toxic at concentrations as low as 2.0 x 10(-7) M due to the generation of free radicals in the presence of this metal ion which enhanced its toxicity to the T. b. brucei parasites. Although some cell division was observed in some of the cells treated with palladium(II) porphyrin, some dividing cells had no nucleus due to unequal division and delivery of the nuclei into the daughter cells. As a result, the rate of cell division decreased with time and cell death occurred within 24 h. Interestingly, trypanosomes treated with metalloporphyrin complexes displayed different morphological features from those cells treated with free base porphyrin or metal ions. Of all the porphyrins and free metal ions tested, only mercury(II) porphyrin and aqueous gold(III) ion were toxic to the trypanosomes in the 10(-7) M range. The chemotherapeutic potential of these observations is discussed.

Effects of the molecular properties of mixed solvents on the elution of alkyl benzoates in RPLC.

The retention behavior and mechanism of methyl, ethyl, propyl, isopropyl, buthyl and isobuthyl benzoates have been studied at different eluent compositions of aqueous mixtures with water-soluble organic solvents (methanol, ethanol, 1-propanol, 2-propanol, acetonitrile (AN), 1,4-dioxane and tetrahydrofuran (THF)) in RPLC. The retention of the solutes is discussed based on the solvent composition, solvent polarity (ETN value), preferential solvation, hydrogen bonding and solvent clusters of the eluents. The smaller ETN values and the larger preferential solvation of the mixed solvent eluted the solutes faster. The IR spectra of HDO suggested that the solvents, except for methanol and ethanol, break the hydrogen bonding between water molecules, resulting in fast elution of the solutes. Based upon the results, we chose an optimum solvent composition for the separation of benzoates and applied it to the determination of the benzoates in clove.

Enhanced conformational changes in DNA in the presence of mercury(II), cadmium(II) and lead(II) porphyrins.

The interactions of the metalloporphyrins of tetrakis (1-methylpyridinium-4yl)porphyrin ([M(TMPyP)](4+)) where M=Hg(II), Cd(II) and Pb(II)) with pBluescript II plasmid DNA have been studied by the measurement of circular dichroism (CD), UV-visible and fluorescence spectra at 0.1 M NaNO(3), pH 7.5 and 25 degrees C. The CD spectra of the DNA changed quite significantly, with the conformational changes in the presence of the metalloporphyrins being much more enhanced compared to that of their free metal ion counterparts. The conformational changes in DNA upon binding to the Hg(II) porphyrin and Hg(II) were, however, different from those of the Cd(II) porphyrin, Pb(II) porphyrin, Pb(II), Cd(II) and H(2)(TMPyP)(4+). In the concentration range of 0-2.30 x 10(-5) M of DNA, the absorption spectra of H(2)(TMPyP)(4+) showed substantial hypochromicity at 423 nm and a red shift of Deltalambda=16 nm in the presence of DNA whereas the Hg(II)-, Pb(II)- and Cd(II) porphyrins showed blue shifts of absorption maximum wavelengths of Deltalambda=-17 nm, Deltalambda=-35 nm and Deltalambda=-4.5 nm, respectively. Furthermore, the shifted absorption maximum wavelengths/nm of the porphyrins in excess amount of DNA were comparable; 438, 439, 440 and 440 for H(2)(TMPyP)(4+), Hg(II)-, Pb(II)- and Cd(II) porphyrins, respectively. The changes in absorption spectra for Hg(II)-, Pb(II)- and Cd(II) porphyrins revealed that these metalloporphyrins dissociated upon binding to DNA which was confirmed by CD as well as fluorescence spectra. The CD results, UV-Vis and fluorescence data indicate that the metalloporphyrins interact differently with DNA based on their binding modes. And the enhanced changes in conformation of DNA in the presence of the metalloporphyrins are due to the synergistic effects of the simultaneous binding of the metal ions and the free base porphyrin to DNA compared to their free metal ion counterparts: [M(TMPyP)](4+)+DNA+2H(+) right harpoon over left harpoon [M(II)(DNA)H(2)(TMPyP)(4+)]. The detailed equilibrium reactions have been described along with suggestions of possible applications in the medical and biological fields.