• Bulletin of the Korean Chemical Society
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• v.21 no.1
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• pp.81-86
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• 2000

In order to obtain detailed information on ground and excited states of curcumin and curcuminoids, as well as to understand the photobiological characteristics of them, their spectral and photophysical behaviors are investigated in various conditions. Various curcuminoids were obtained and their structures were determined by spectroscopic methods. In n-hexane, the absorption and fluorescence spectra of these compounds contain some structure, which disappear in more polar solvent such as methanol. The fluorescence intensities of curcumin and dimethylated curcumin decrease as the concentration of water increases. The intensities also decrease as the solvent varies from neutral to extremely acidic (lower than pH 1.5) or to basic (higher than pH 8.0) condition. These results indicate that the spectral and photophysical properties of both of curcumin and curcuminoids are strongly influenced by solvent, water, and pH.

• Carbon letters
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• v.12 no.3
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• pp.152-161
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• 2011

Activated carbon was prepared from pre-carbonized petroleum coke. Textural properties were determined from studies of the adsorption of nitrogen at 77 K and the surface chemistry was obtained using the Fourier-transform infrared spectrometer technique and the Boehm titration process. The adsorption of three aromatic compounds, namely phenol (P), p-nitrophenol (PNP) and benzoic acid (BA) onto APC in aqueous solution was studied in a batch system with respect to contact time, pH, initial concentration of solutes and temperature. Active carbon APC obtained was found to possess a high surface area and a predominantly microporous structure; it also had an acidic surface character. The experimental data fitted the pseudo-second-order kinetic model well; also, the intraparticle diffusion was the only controlling process in determining the adsorption of the three pollutants investigated. The adsorption data fit well with the Langmuir and Freundlich models. The uptake of the three pollutants was found to be strongly dependent on the pH value and the temperature of the solution. Most of the experiments were conducted at pH 7; the $pH_{(PZC)}$ of the active carbon under study was 5.0; the surface of the active carbon was negatively charged. The thermodynamic parameters evaluated for APC revealed that the adsorption of P was spontaneous and exothermic in nature, while PNP and BA showed no-spontaneity of the adsorption process and that process was endothermic in nature.

• The Korean Journal of Physiology
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• v.11 no.2
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• pp.1-7
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• 1977

The activity of the $Ca^{++}$ activated adenosinetriphosphatase (Ca-ATPase) of actomyosin systeme of rabbit and frog skeletal muscle has been studied at varying pH and temperature. The PH optima of the Ca-ATPase activity of the rabbit actomyosin was rather broad. Over the temperature range of $16-36^{\circ}C$ activity of the enzyme was not appreciably changed between pH 6.4-8.5; below and above which it rapidly reduced. The pH at the inflection point of the enzyme activity increased as temperature decreased, showing the ${\bigtriangleup}pH\;inflection/{\bigtriangleup}T$ of approximately $-0.018\;unit/^{\circ}C$. Consequently, $(OH^-)/(H^+)$ ratio at the inflection point was constant regardless of assay temperature. In the frog actomyosin systems the Ca-ATPase activity was not apparently altered between PH 6.4-7.0 when the incubation temperature was $15{\sim}30^{\circ}C$. Outside of this range of pH, however, the enzyme activity was dramatically decreased. The pH of the inflection point changed inversely with temperature. ${\bigtriangleup}pH\;inflection/{\bigtriangleup}T$ at the acidic side was approximately $-0.018\;unit/^{\circ}C$, whereas that at the alkaline side it was about $-0.037\;unit/^{\circ}C$. The Arrhenius Plot on the Ca-ATPase activity at constant $(OH^-)/(H^+)$ ratio of 1.0 was not linear, but showed break at arround $20^{\circ}C$ for both rabbit and frog actomyosin Preparations. From these results it was speculated that pH dependence of Ca-ATPase activity of rabbit actomyosin systems might reflect titrations of histidine-imidazole and -SH groups, and that of the frog actomyosin represents titrations of histidine-imidazole and lysyllysine ${\alpha}-NH_2$ groups.

• Clean Technology
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• v.7 no.1
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• pp.75-80
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• 2001

In this study, hexavalent chromium (Cr(VI)) plating wastewater in strong acidic condition was treated by reduction and alkalization. Ferrous sulfate ($FeSO_4$), known to reduce Cr(VI) to Cr(III) rapidly at acidic pH, was used as a reductant of Cr(VI). The optimum reduction condition of Cr(VI) was observed at iron to chromium dose ratio of 3:1 by mole concentration. The precipitation of Cr(III) as $Cr(OH)_3$, was achieved by the pH adjustment in the limestone aeration bed. The precipitates were removed less than the upper limit of chromium for effluent at pH over 5.0. The continuous removal of Cr(VI) was performed using the process consisting of reduction vessel, limestone aeration bed, and sedimentation tank coupled with metal screen membrane. As pH was maintained around 5.0 in the limestone aeration bed, insoluble chromic hydroxide flocs was formed continuously. Most chromic hydroxide flocs were filtered by the metal screen membrane with 1450 mesh size, and the treated water to meet the upper limits of chromium for effluent (Cr Conc. 0.25~0.90 mg/l) was obtained in 30 minutes. Periodic backwashing decreased the fouling on the membrane rapidly.

• Proceedings of the KSR Conference
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• 2004.06a
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• pp.171-176
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• 2004

Electro chemical corrosion tests were conducted on two structural steels, SS400 and SM490A, in various solutions with different pH values, All materials showed typical active corrosion behaviors in the solutions, and corrosion potential and current density were measured from the slopes obtained from the Tafel curves using linear polarization method. Corrosion potential increased in the acidic region and then decreased depending on the pH values of the solutions. All materials showed the fast corrosion rate in artificial acid rain(pH=4.7), but the slower corrosion rate was observed in NaOH solution(pH=12.0) for SS400 and in distilled water(pH=7.0) for SM490A, respectively, which is thought to come from the difference in chemical composition of two alloys. Generally homogeneous corrosion occurred in acid rain condition, and almost no corrosion was observed in distilled water in both alloys. NaOH solution produced more corrosion than distilled water, and more corrosion had progressed in SS400 than in SM490A in $3.5\%$ NaCl solution.

• Environmental Mutagens and Carcinogens
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• v.15 no.2
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• pp.106-114
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• 1995

A method was developed to detect total mutagenicity of fried fish for S. typhimurium TA98, using Ames assay. Method described herein circumvented problems associated with the sample preparation for Ames assay, i.e., a multi-purification step of sample and interference with solvent residuals. Experiment A, the best method developed in the present study, consisted of two important steps: pH adjustment of the aqueous sample solution from fried fish samples to remove impurities, and simultaneous distillation extraction (SDE) for partially purified samples to remove volatile compounds from solvents. The procedure and results were described as below. Fillet of gizzard shad (Konosirus punctatus) fish sample fried for 10 min each side on the temperature-controlled fry-pan (210$\circ$C) was homogenized in an aqueous acidic solution (pH 2) with a homogenizer, followed by filtration through Celite. The tiltrate (pH 2), removed some impurities by extraction with chloroform:methanol (2:1, v/v) mixture, was adjusted pH to 10 and then centrifuged to remove precipitate. The ethylacetate extract from the tiltrate of pH 10 was rotoevaporated and purified by SDE apparatus for 2 hours. Experiment A revealed significantly higher revertants (1928 per 25 g fried sample) than other Experiment (B, C, or D) tested. Experiment A gave good results in the mutagenicity test of fried fish sample with few purification steps using only 25 g fried sample and 650 ml of solvents; and thus this method could be a useful tool for the screening the mutagenicity or antimutagenicity of other foods as well.

• Korean Journal of Materials Research
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• v.15 no.6
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• pp.426-430
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• 2005

Chemical mechanical polishing (CMP) is an essential process in the production of integrated circuits containing copper interconnects. The effect of alanine in reactive slurries representative of those that might be used in copper CMP was studied with the aim of improving selectivity between copper(Cu) film and tantalum-nitride(TaN) film. We investigated the pH effect of nano-colloidal silica slurry containing alanine through the chemical mechanical polishing test for the 8(inch) blanket wafers as deposited Cu and TaN film, respectively. The copper and tantalum-nitride removal rate decreased with the increase of pH and reaches the neutral at pH 7, then, with the further increase of pH to alkaline, the removal rate rise to increase soddenly. It was found that alkaline slurry has a higher removal rate than acidic and neutral slurries for copper film, but the removal rate of tantalum-nitride does not change much. These tests indicated that alanine may improve the CMP process by controlling the selectivity between Cu and TaN film.

• Applied Biological Chemistry
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• v.12
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• pp.7-11
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• 1969

Mucor-rennin, the crystalline milk-clotting enzyme, isolated from Mucor pusillus var. Lindt, has an acid protease activity. The optimum pH for the digestion of k-casein is 4.5, while that for hemoglobin digestion is 4.0. The skim milk solution was easily clotted acidic solution than alkalin solution, and the milk clotting activated by Ca ion. The enzyme was heat stable against heat from pH 4.0 to 6.0 but was more stable at pH 5.0. The activity of the enzyme at pH 5.0 did not decrease at 30 C for 15 days and the activity was not effected by sodium propionate and salicilic acid. Therefore, the enzyme of liguid type could store for a long time and could be transported from Erzyme production Co. to Manufacture of cheese Co. by adding the antiesptic and by adjusting pH to 5.0.

• Bulletin of the Korean Chemical Society
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• v.33 no.4
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• pp.1290-1296
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• 2012

Fenton reaction and iron autoxidation have been debated for the major process in ROS mediated DNA cleavage. We compared both processes on iron oxidation, DNA cleavage, and cyclic voltammetric experiment at different pHs. Both oxidation reactions were preferred at basic pH condition, unlike DNA cleavage. This indicates that iron oxidation and the following steps probably occur separately. The ROS generated from autoxidation seems to be superoxide radical since sod exerted the best inhibition on DNA cleavage when $H_2O_2$ was absent. In comparison of cyclic voltammograms of $Fe^{2+}$ in NaCl solution and phosphate buffer, DNA addition to phosphate buffer induced significant change in the redox cycle of iron, indicating that iron may bind DNA as a complex with phosphate. Different pulse voltammogram in the presence of ctDNA suggest that iron ions are recyclable at acidic pH, whereas they may form an electrically stable complex with DNA at high pH condition.

• Biotechnology and Bioprocess Engineering:BBE
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• v.3 no.2
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• pp.78-81
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• 1998

Cyclodextrin glucanotransferase [CGTase, E.C.2.4.1.19] is an extracellular enzyme, which catalyzes he formation of ${\alpha}$-, ${\beta}$-, ${\gamma}$- CDs from starch. Their proportions of formations depend on enzyme sources and reaction conditions. To understand what determines the product specificity of CGTases, we examined the alteration of product specificity of CGTase from Bacillus macerans by organic solvent sand pH. At acidic pH range less than pH 6 where the enzyme was unstable, the ratio of ${\alpha}$-/ ${\beta}$-CD production was increased 4 times more than that at neutral pH range. As we increased the concentration of 2-butanol, ${\alpha}$-/ ${\beta}$-CD ratio was proportionally increased but / ratio remained constant. The ${\alpha}$-/ ${\beta}$-CD ratio of products was increased in the reaction media which yielded low products.