• Bulletin of the Korean Chemical Society
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• 제25권4호
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• pp.517-524
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• 2004

Two simple and sensitive spectrophotometric methods were developed for the determination of carbocisteine, penicillamine, ethionamide and thioctic acid in bulk and in their pharmaceutical preparations using alkaline potassium permanganate as an oxidizing agent. The first one involves determination of ethionamide and thioctic acid by spectrophotometric investigation of the oxidation reaction of the two drugs. The second method involves determination of carbocisteine and penicillamine by kinetic studies of the oxidation reaction of these two drugs at room temperature for a fixed time of 20 minutes. The absorbance of the colored manganate ions was measured at 610 nm in both methods. 1-10 ${\mu}$g/mL of ethionamide and thioctic acid could be etermined by the spectrophotometric method with detection limits of 0.11 and 0.089 ${\mu}$g/mL for the two drugs respectively. 2-10 ${\mu}$g/mL of carbocisteine and penicillamine could be determined by the kinetic method with detection limits of 0.14 and 0.21 ${\mu}$g/mL respectively. The two methods were successfully applied for the determination of these drugs in their dosage forms.

• Bulletin of the Korean Chemical Society
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• 제27권6호
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• pp.863-868
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• 2006

The partial least squares (PLS-1) calibration model based on spectrophotometric measurement, for the simultaneous determination of sulfite and sulfide is described. This method is based on the difference between the rate of the reaction of sulfide and sulfite with Malachite Green in pH 7.0 buffer solution and at 25 ${^{\circ}C}$. The absorption kinetic profiles of the solutions were monitored by measuring the decrease in the absorbance of Malachite Green at 617 nm in the time range 10-180 s after initiation of the reactions with 2 s intervals. The experimental calibration matrix for partial least squares (PLS-1) calibration was designed with 24 samples. The cross-validation method was used for selecting the number of factors. The results showed that simultaneous determination could be performed in the range 0.030-1.5 and 0.030-1.2 $\mu$g m$L ^{-1}$ for sulfite and sulfide, respectively. The proposed method was successfully applied to simultaneous determination of sulfite and sulfide in water samples and whole human blood.

• Bulletin of the Korean Chemical Society
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• 제24권9호
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• pp.1261-1264
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• 2003

A method for the determination of trace amount of sulfide based on the addition reaction of sulfide with methyl green at pH 7.5 and $25{\circ}C$ is described. The reaction is monitored spectrophotometrically by measuring the decrease in absorbance of the dyestuff at 637 nm by the initial rate and fixed time method. The calibration graph is linear in the range 30-1200 ppb. The theoretical limit of detection was 0.014 ppm. Seven replicate analysis of a sample solution containing 0.70 ppm sulfide gave a relative standard deviation of 1.5%. The interfering effects of various ions on sulfide determination have been reported and procedures for removal of interference have been described. The proposed method was applied successfully to the determination of sulfide in tap and wastewater samples.

• Bulletin of the Korean Chemical Society
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• 제23권12호
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• pp.1816-1818
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• 2002

• BMB Reports
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• 제39권4호
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• pp.426-431
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• 2006

Embryonic stem cells (ESCs), representing a population of undifferentiated pluripotent cells with both self-renewal and multilineage differentiation characteristics, are capable of spontaneous differentiation into cardiomyocytes. The present study sought to define the kinetic characterization of lactate dehydrogenase (LDH) and creatine kinase (CK) of ESC- and neonatal-derived cardiomyocytes. Spontaneously differentiated cardiomyocytes from embryoid bodies (EBs) derived from mouse ESC line (Royan B1) and neonatal cardiomyocytes were dispersed in a buffer solution. Enzymes were extracted by sonication and centrifugation for kinetic evaluation of LDH and CK with spectrophotometric methods. While a comparison between the kinetic properties of the LDH and CK of both groups revealed not only different Michaelis constants and optimum temperatures for LDH but also different Michaelis constants and optimum pH for CK, the pH profile of LDH and optimum temperature of CK were similar. In defining some kinetic properties of cardiac metabolic enzymes of ESC-derived cardiomyocytes, our results are expected to further facilitate the use of ESCs as an experimental model.

• 한국미생물·생명공학회지
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• 제29권2호
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• pp.90-95
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• 2001

Cysteine 계 cathepsin B 단백질 분해 효소는 고등동물의 세포조직 내에 lysosome에 존재하며 병원성세균의 침입을 막고 불필요한 단백질을 분해시키며 또한 면역세포의 항원인식에 대한 단백질 생산 등에 관여하는 효소이다. 이 cathepsin B의 과량 발현은 암전이, 만성적 염증성 질환, 류머티스 관절염, 노인성치매 등의 원인이 된다. 이 cathepsin B를 저해하는 것으로 밝혀진 S. luteogriseus KT-10으로부터 분리한 저해제 KHS10을 이용하여 분광광도계를 사용, 그 저해력을 조사하였다. Cathepsin B 저해제 KHS10은 경쟁적 저해를 나타내며 cathepsin B는 기질 CLN에 대해 Km 값은 0.5mM을 Vmax 값은 $29.4\mu$M로 나타내었으며, 합성기질인 BANA에 대해서는 Km 값이 2mM을 Vmax 값은 7.8$\mu$M/min로 나타났다. 저해제 KHS10의 Ki 값은 $0.43{\mu}$M로 측정되었다. Cathepsin B에 대한 저해제 KS10의 반응시간에 대한 저해력은 1시간 반응시 저해력이 100%에 가깝게 높게 나타났으며 온도에 의한 저해율은 $25^{\circ}C$에서 활성이 가장 높게 나타났다. Cathepsin B와 저해제 KHS10이 반응 전 배양은 5분간의 전 배양으로 높은 저해율을 나타내었으며 또한 pH에 의한 저해활성은 pH 6.0에서 가장 높게 저해하는 것으로 조사되었다. 저해제 KHS10는 $100^{\circ}C$에서 1시간 열을 가해도 그 잔류 저해력은 80% 이상 유지되었다.

• Bulletin of the Korean Chemical Society
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• 제31권7호
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• pp.1907-1914
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• 2010

A novel catalytic kinetic method is proposed for the determination of Se(IV), Se(VI) and total inorganic selenium in water based on the catalytic effect of Se(IV) on the reduction of bromate by p-nitrophenylhydrazine at pH 3.0. The generated bromine, $Br_2$ or $Cl_2$ plus $Br_2$ in 0.1 M NaCl (or NaBr) environment efficiently decolorized Calmagite and the reaction was monitored spectrophotometrically at 523 nm as a function of time. In this indicator reaction, bromide acted as an activator for the catalysis of selenium (IV) and a reducing agent for selenium (VI) at pH 3.0, which allowed the determination of total selenium. The fixed time method was adopted for the determination and speciation of inorganic selenium. Under the optimum conditions, the calibration graph are linear in the range 1 - 35 ${\mu}gL^{-1}$ of Se(IV) for the fixed time method at $25^{\circ}C$. The detection limit based on statistical $3S_{blank}$/m-criterion was 0.215 ${\mu}gL^{-1}$ for the fixed time method (7 min). All of the variables that affect the sensitivity at 523 nm were investigated, and the optimum conditions were established. The interference effect of various cations and anions on the Se (IV) determination was also studied. The selectivity of the selenium determination was greatly improved with the use of the strongly cation exchange resin such as Amberlite IR120 plus. The proposed kinetic method was validated statistically and through recovery studies in natural water samples. The RSDs for ten replicate measurements of 5, 15 and 25 ${\mu}gL^{-1}$ of Se(IV) and Se(VI) was changed between 2.1 - 4.85%. Analyses of a certified standard reference material (NIST SRM 1643e) for selenium using the fixed-time method showed that the proposed kinetic method has good accuracy. Se(IV), Se(VI) and total inorganic selenium in environmental water samples have been successfully determined by this method after selective reduction of Se(VI) to Se(IV).

• 대한화학회지
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• 제43권1호
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• pp.85-91
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• 1999

Phenyl N,N-diethyl-P-benzylphonamidate 및 그 유도체들의 염기성 가수분해 반응속도 상수를 분광 광도법으로 측정하였다. 속도 상수로부터 열역학적 파라메타(Ea, ${\Delta}H^{\neq}$,${\Delta}S^{\neq}$)를 구하였고, 이탈기의 치환기 효과는 Hammett 식을 이용하여 얻었다. 이들 실험 자료에 의하면 가수분해 반응은 활성화 엔트로피가 양의 값이나 작은 음의 값을 갖고 카르보음이온 생성이 수반되는 해리반응 보다는 이중피라미드 중간체 또는 전이 상태를 경유하는 회합 메카니즘을 강력히 암시하고 있다. 반응속도론적 연구 결과에 의하면 치환 pheny N,N-diethyl-P-benzylphosphonamidates의 가수분해 반응은 회합성 메카니즘으로 진행됨을 알 수 있었다.

• 대한화학회지
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• 제30권5호
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• pp.409-414
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• 1986

황산용액에서 에탄올에 의한 $VO_2^+$이온을 환원시키면 황산바나딜(IV)가 생성된다. 생성물 VOS$O_4$를 포함하는 용액에 대한 분광학적 결과가 보고된다. 에탄올에 의한 $VO_2^+$의 환원에 대한 속도론적 연구는 35${\circ}C$와 50${\circ}C$에서 행하여 졌다. $VO_2^+$의 환원반응메카니즘이 논의되었다.

• Journal of Microbiology and Biotechnology
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• 제5권6호
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• pp.315-318
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• 1995

Sulfanilic acid (4-aminobenzenesulfonic acid) alone is normally not permeant in bacteria but can be readily delivered via the microbial dipeptide transport system. A dipeptidyl derivative of this compound, L-phenylalanyl-L-2-sulfanilylglycine (PSG), prepared by attachment of its primary amino group to the phenylalanyl $\alpha$-glycine moiety, appeared to have a Km of 0.125 mM and a Vmax of 1.9 nmoles/ml/min ($A_{660}$, 1.0) in Escherichia coli. From competitive spectrophotometric analysis, it was found that the type of amino acids in both of the N- and C-terminals affected the kinetic power of dipeptides. The growth inhibitory effect of PSG was over 7 times more potent than that of the sulfanilic acid against E. coli, suggesting that this potential inhibition was presumably due to the increased hydrophobic nature of the sulfanilyl dipeptide.