• Archives of Pharmacal Research
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• 제19권4호
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• pp.269-274
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• 1996

The binding interactions between human serum albumin (HSA) and the edible food dyes amaranth, tartrazine and sunset yellow have been studied. Intrinsic association constants and the free energy changes associated with dye-protein binding at physiological pH for amaranth and tartrazine, and at two different pH values for sunset yellow have been calculated from ultrafiltration data. The temperature dependence $(20-40^{\circ}C)$ of the intrinsic association constants at pH 7.4 for amaranth-HSA and tartrazine-HSA mixtures have been measured, from which a plot of the van't Hoff isochore exhibits a marked change in slope around $30^{\circ}C$ indicating a possible change in protein conformation. The number of dye binding sites on HSA is reported for all the above conditions. HSA-ligand binding enthalpies have been used in conjunction with the N-B transitional binding enthalpy for HSA, to calculate the enthalpy for the N-B transition when ligands are bound with the protein.

• Archives of Pharmacal Research
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• 제14권2호
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• pp.118-123
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• 1991

Potentially dangerous nitrosamines have been shown to result from the reaction of sodium nitrogusside with several drugs under physiological conditions (pH 7.3 and $37^\circ{C})$. In each case the products were identical to those produced upon reaction with nitrous acid at much lower pH values. Reaction rates were shown to reflect a first order dependence on both amine and nitroprusside concentrations and to increase at higher pH values, approximately in proportion to concentrations of unprotonated amine. Fast reactions of sodium nitroprusside with reduced glutathione, cysteine, and ascorbate suppress but do not prevent the conversion of amines into N-nitrosamines. These results show sodium nitroprusside to be very potent nitrosating agent under physiological conditions and suggested nitrosamines may be formed during its normal pharmacological administration.

• 한국의류학회지
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• 제14권2호
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• pp.98-103
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• 1990

Fibrous adsorbents containing amidoxime group which make chelate complexes with uranyl ions are studied for the recovery of uranium from sea water. Acrylic fibers are used as base Polymer. The adsorption properties of uranium are carried out to examine pH effect, concen-tration dependence, adsorption rate, separation, and chelate complex. The results obtained are as follows; 1. Metal capacity of U (VI) ion is in the range of pH $2\~10.2$. Amidoxime group-containing fiber recover U (VI) ions existed in sea water or waste water in extremely small quantities. 3. Using amidoxime group-containing fiber Cu (II) and U (VI) are separated with each other in dilute nitric acid solution (pH 2.3). 4. U (VI) chelate complexes are conformed by tridendate ligands, which are coordinated with one nitrogen and two oxygens onto amidoxime group-containing fiber.

• Biomolecules & Therapeutics
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• 제20권2호
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• pp.234-238
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• 2012

Propofol is an anesthetic commonly used to provide sedation or to induce and maintain an anesthetic stated. However, there are reports which indicate propofol may cause psychological dependence or be abused. In the present study, we used various behavioral tests including climbing test, jumping test, conditioned place preference, and self-administration test to assess the dependence potential and abuse liability of propofol compared to a positive control (methamphetamine) or a negative control (saline or intralipid). Among the tests, the conditioned place preference test was conducted with a biased method, and the selfadministration test was performed under a fixed ratio (FR) 1 schedule, 1 h per session. No difference was found in the climbing test and jumping test, but propofol (30 mg/kg, i.p.) increased the rewarding effect in the conditioned place preference test, and it showed a positive reinforcing effect compared to the vehicle. These results indicate that propofol tends to show psychological dependence rather than physical dependence, and it seems not to be related with dopaminergic system.

• 한국응용과학기술학회지
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• 제8권1호
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• pp.59-67
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• 1991

The reactions of semicarbazide hydrochloride with aliphatic and alicyclic ketones were studied kinetically at 15, 25, 35 and 45$^{\circ}C$ in 20% ethanol solution buffered at pH 2.9. The rate of cyclohexanone semicarbazone formation is 5.5 times as fast as that of cyclopentanone semicarbazone, while 3-pentanone semicarbazone is 4.7 times as slow as that of 2-pentanone, The activation energy of cyclohexanone, 2-pentanone, 2 hexanone, cyclopentanone, 4-methyl-2-pentanone and 3-pentanone semicarbazone formation are calculated 5.08, 7.52, 8.79, 9.59, 9.49, 11.59, respectively. It is concluded from the effect of ionic strength that the reaction is affected by not ion but neutral molecules being progressed hydrogen bond between oxygen atom of carbonyl group and hydrogen atom of acid-catalyst and concerted nucleophilic attack of free base on the carbonly compound. Dependence on pH of the rate of 2-pentanone semicarbozone formation is linear relationship below pH 4.60 and above pH 5.60. As a result of studing citric acid catalysis, second order constants increase linearly with citric acid concentration. As the catalyst concentration is varied from 0.025 to 0.10 mol/1 at pH 2.90, the rate constants increase 1.4 times, but slight increase is observed at pH 5.60. Conclusively, the rate-determining step is formation of tetrahedral interemediate below pH 4.65 and dehydration between pH 5.60 and pH 7.11. It is concluded that the formation reaction of cyclohexanone semicarbazone is faster than cyclopentanone semicarbazone due to the steric strain in the process of forming tetrahedral intermediate.

• 한국토양비료학회지
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• 제38권5호
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• pp.247-252
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• 2005

토양 pH는 토양화학반응의 결과로 토양용액으로 해리하는 수소이온을 나타내는 intensity factor이고 토양의 알루미늄에 의하여 수소이온이 완충되고 있다. 토양 양이온에 의하여 알루미늄의 수소이온 완충기능이 저하되면 토양 pH 양상이 달라지므로 토양 EC에 따른 토양 pH 양상은 토양의 pH 완충력 등 토양관리를 위한 중요한 정보를 담고 있다. 토양에 투입되는 양분에 의하여 토양 pH가 달라지는 현상을 구명하고 시설재배지 토양의 EC에 따른 토양 pH 양상을 파악하기 위하여 사양토에는 가축분과 퇴비 및 비료를 넣고 시설재배지 토양은 무처리 상태로 $30^{\circ}C$에서 5, 10, 20, 40일간 호기항온 후 토양과 토양용액의 화학적 특성을 분석하였다. 가축분을 첨가한 사양토의 pH 양상은 토양에 첨가된 양이온 함량에 비례하여 pH가 올라갔으며 양분이 축적된 시설토양의 pH 양상은 양분함량이 많을수록 pH가 낮아졌다. 따라서 토양 EC가 높아질 때 토양 알루미늄의 수소이온 완충력이 높은 상태에서는 토양의 pH는 양이온의 양에 비례하여 올라가지만 토양 알루미늄의 수소이온 완충력이 저하된 상태에서는 토양의 음이온의 양에 비례하여 pH가 낮아지는 것으로 나타났다.

• Bulletin of the Korean Chemical Society
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• 제29권4호
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• pp.785-789
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• 2008

The present study is the first report of utilizing $TiO_2$ photocatalyst to analytically calibrate the hydroperoxyl radical ($HO_2\;^{\cdot}$). An in-situ calibration method of $HO_2\;^{\cdot}$ is proposed for air monitoring by using an 2-methyl-6-(pmethoxyphenyl)- 3,7-dihydroimidazo-[1,2-a]pyrazin-3-one (MCLA)-chemiluminescence (CL) technique. In this method, $HO_2\;^{\cdot}$($pK_a$ = 4.80) is produced by the ultraviolet (UV) photolysis of immobilized $TiO_2$ using a constant flow rate of air equilibrated water, in which $HO_2\;^{\cdot}$ is controlled by using various lengths of knotted tubing reactor (KTR). The principle of the proposed calibration is based on the experimentally determined halflife ($t_{1/2}$) of $HO_2\;^{\cdot}$ and its empirically observed pH-dependent rate constant, $k_{obs}$, at a given pH. The concentration of $HO_2\;^{\cdot}$/$O_2\;^{\cdot}$− is increased as pH increases. This pH dependence is due to the different disproportionative reactivities between $HO_2\;^{\cdot}$/$O_2\;^{\cdot}$− and $HO_2\;^{\cdot}$/$O_2\;^{\cdot}$−. Experimental results indicate the practical feasibility of the approach, producing very promising method.

• Bulletin of the Korean Chemical Society
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• 제8권4호
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• pp.280-285
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• 1987

FMN-dependent glycolate oxidase from spinach is inactivated by diethyl pyrocarbonate at pH 7.0. Inactivation of both apo- and holoenzyme by diethyl pyrocarbonate follows pseudo-first-order kinetics and first order with respect to the reagent. A series of difference spectra of inactivated and native enzymes show a single peak at 240 nm, indicating the modification of histidyl residues. No decrease in absorbance at around 280 nm due to formation of O-carbethoxytyrosine is observed. The rate of inactivation is dependent on pH, and the data for pH dependent rates implicate the involvement of a group with a pKa of 6.9. The activity lost by treatment with diethyl pyrocarbonate could be almost fully restored by incubation with 0.75M hydroxylamine. The reactivation by hydroxylamine and the pH dependence of inactivation are also consistent with that the inactivation is due to modification of histidyl residues. Although coenzyme FMN is without protective effect, the substrate glycolate, the product glyoxylate, and two competitive inhibitors, oxalate and oxalacetate, provide marked protection against the inactivation of the holoenzyme. These results suggest that the inactivation of the oxidase by diethyl pyrocarbonate occurs by modification of essential histidyl residue(s) at the active site.

• Bulletin of the Korean Chemical Society
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• 제4권2호
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• pp.68-72
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• 1983

The $pK_{a}$ of $-NH_{3}^{+}$ group of chitosan in water was 6.2, while that of D-glucosamine-HCl, monomer of chitosan, was found to be 7.8. The difference of $pK_{a}$ values between chitosan and D-glucosamine was attributed to the strong electrostatic interaction between $-NH_{3}^{+}$ groups in chitosan. The apparent binding constant of $Cu^{2+}$ to D-glucosamine was estimated to be $1{\times}10^{4}$. For chitosan, no significant binding of $Cu^{2+}$ to the polymer was observed when pH < 5, but strong cooperative binding was observed near pH 5.1. The mechanism of such cooperativity was proposcd. Chitosan in solution exhibited typical polyelectrolytic behaviors: viscosity increases with increased amount of charged group, and decreases with addition of salt. The concentration dependence of viscosity was measured, and the Huggins parameters and intrinsic viscosity were calculated at various ionic strength. The results were interpreted in terms of molecular properties of the chitosan molecule.

• 한국식품위생안전성학회지
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• 제33권1호
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• pp.71-76
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• 2018

노로바이러스는 전 세계적으로 산발적인 발병 관련 비세균성 위장염의 주요 원인 물질이다. 노로바이러스 검출을 위해 역전사 실시간 PCR (RT qPCR)이 그 민감도와 특이성으로 인해 주요 수단으로 빠르게 자리 잡았다. 그러나 RT qPCR 분석을 위해서는 정확한 바이러스 RNA 추출방법이 필수적이다. TRIzol 시약은 생물학적 물질로부터 RNA의 추출에 이용되고 따라서 노로바이러스 RNA 추출에도 널리 사용된다. 이 연구에서는 인체 노로바이러스 유전체 그룹 I (GI) 및 유전자 그룹 II (GII)와 생쥐 노로바이러스(GV) 중에서 GII로부터의 TRIzol 을 이용한 바이러스 RNA의 추출률이 바이러스 시료 용액의 pH에 의존했다는 내용이 다루어졌다. 실시간 PCR의 Ct값으로 비교한 RNA 추출 수율은 산성 영역보다 알칼리성 pH에서 높았다. 이 연구 결과로 부터 TRIzol을 이용하여 GII RNA를 추출하여 노로바이러스를 정량적으로 분석할 때 pH조건이 대단히 중요하다는 것을 알 수 있었다.