• Journal of Microbiology
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• 제39권3호
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• pp.149-153
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• 2001

The electron transfer reaction is one of the most essential processes of life. Not only does it provide the means of transforming solar and chemical energy into a utilizable form for all living organisms, it also extends into a range of metabolic processes that support the life of a cell. Thus, it is of great interest to understand the physical basis of the rates and reduction potentials of these reactions. To identify the major determinants of reduction potentials in redox proteins, we have chosen the simplest electron transfer protein, rubredoxin, a small (52-54 residue) iron-sulfur protein family, widely distributed in bacteria and archaea. Rubredoxins can be grouped into two classes based on the correlation of their reduction potentials with the identity of residue 44; those with Ala44 (ex: Pyrococcus furiosus) have reduction potentials that are ∼50 mV higher than those with Va144 (ex: Clostridium pasteurianum). Based on the crystal structures of rubredoxins from C. pasteurianum and P. furiosus, we propose the identity of residue 44 alone determines the reduction potential by the orientation of the electric dipole moment of the peptide bond between 43 and 44. Based on 1.5 $\AA$ resolution crystal structures and molecular dynamics simulations of oxidized and reduced rubredoxins from C. pasteurianum, the structural rearrangements upon reduction suggest specific mechanisms by which electron transfer reactions of rubredoxin should be facilitated.

• 한국식품과학회지
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• 제2권2호
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• pp.34-37
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• 1970

김치(동치미) 발효기간 중 산도 pH 및 산화환원전위를 측정한 결과 다음의 사실을 얻었다. 1. 산도는 젖산으로서 3.5%에 달하고 pH는 3.4까지 저하되었다. 2. 산화환원전위는 발효초기에는 상당히 높은 값인 10이상을 나타내고 발효최성기에는 15에서 2까지 저하되며 말기에서는 도리어 약간 상승하는 경향이었다. 3. 산화환원전위를 보아 김치발효 초기가 말기보다 호기적 상태임을 알 수 있었다.

• Bulletin of the Korean Chemical Society
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• 제12권5호
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• pp.487-490
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• 1991

Electrochemical studies of alkali metal cations $(Na^+, K^+, Rb^+, Cs^+)$ were performed in methanolic solutions of 18-crown-6 and tetrabutylammonium salts at dropping mercury electrodes (DME) and thin mercury film electrodes (TMFE). All the cations investigated were reduced reversibly at DME in the absence and presence of 18-crown-6, and in the latter the limiting currents were decreased and the reduction potentials shifted to the negative direction. The reduction potentials of the metal ions (0.2 mM) in the presence of the crown (10 mM) were - 2.14 $(Na^+)$, - 2.26 $(K^+)$, - 2.20 $(Rb^+) and - 2.14 $(Cs^+)$ V vs. SCE, respectively. The measured potentials were rationalized with ion recognition of the cations by the crown. Electroreduction at TMFE were highly irreversible. A new representation method of ion recognition is presented. In aqueous solutions, electroreduction of the alkali metal ions were characterized by adsorption.

• Archives of Pharmacal Research
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• 제22권4호
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• pp.335-339
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• 1999

The oxidation-reduction potentials of cosmetic raw materials, showing tyrosinase inhibitory action, and phenolic compounds structurally similar to L-tyrosine were determined by cylcic voltammetry. The voltammograms obtained could be classified ito 4 patterns (patterns 1-4). Patterns 1, characterized by oxidation and reduction peaks as a pair, was observed with catechol, hydroquinone or phenol, and pattern 2 exhibiting another oxidation peak in addition to oxidation and reduction peaks as a pair was found with arbutin, kojic acid, resorcinol, methyl p-hydroxybenzoate and L-tyrosine as the substrate of tyrosinase. Pattern 3 with an independent oxidation peak only was expressed by L-ascorbic acid, and pattern 4 with a reduction peak only at high potentials, by hinokitiol. The tyrosinase inhibitory activity of these compounds was also evaluated using the 50% inhibitory concentration ($IC_{50}$) and the inhibition constant (Ki) as parameters. Hinokitiol, classified as patterns 4, showed the highest inhibitory activity (lowest $IC_{50}$ and Ki). Hydroquinone showing the second highest activity belonged to pattern 1, which also included compounds exhibiting pattern 2 was relatively low with Ki values being in the order of 10-4 M. Although there was no consistent relationship between oxidation-reduction potentials and tyrosinase inhibitory action, the voltammetry data can be used as an additional index to establish the relationship between the structure and the tyrosine inhibitory activity.

• Bulletin of the Korean Chemical Society
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• 제15권7호
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• pp.563-567
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• 1994

The electroreduction of dioxygen at glassy carbon electrodes with irreversible self-assembly of N-hexadecyl-N'-methyl viologen $(C_{16}VC_1)$ proceeds at potentials more positive than those where the reduction occurs at bare electrodes. The electrocatalyzed reduction takes place at potentials well ahead of those where the catalyst is reduced in the absence of dioxygen and the limiting currents observed at rotating disk electrodes did not deviate from the thoretical Levich line up to 6400 rpm, indicating that the electrocatalysis is extremely rapid. The rate constant for the heterogeneous reaction between $C_{16}V^+C_1$ immobilized on the electrode surface and $O_2$ in solution was estimated to be ca. $10^8\;M^{-1}s^{-1}$. The half-wave potential of dioxygen reduction was independent of solution pH.

• Journal of Electrochemical Science and Technology
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• 제4권3호
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• pp.93-101
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• 2013

The electrodeposition of indium onto a copper electrode from an aqueous sulfate solution containing $In^{3+}$ was studied by means of cyclic voltammetry and chronoamperometry. Reduction and oxidation of indium on copper were investigated by using cyclic voltammograms at different negative limiting potentials and at different scan rates in cumulative cycles. Cyclic voltammograms indicated that reduction and oxidation processes of indium could involve various reactions. Chronoamperometry was carried out to analyze the nucleation mechanism of indium in the early stage of indium electrodeposition. The non-dimensional plot of the current transients at different potentials showed that the shape of the plot depended on the applied potential. The nucleation of indium at potential step of -0.6~-0.8 V was close to progressive nucleation limited by diffusion. However the non-dimensional plot of current transients for the indium nucleation showed different behaviors from theoretical curves at the potential step lower than -0.8 V.

• Bulletin of the Korean Chemical Society
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• 제33권11호
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• pp.3889-3890
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• 2012

• Journal of Korean Neurosurgical Society
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• 제63권2호
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• pp.202-209
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• 2020

Objective : The purpose of this study was to evaluate the efficacy of the anterior approach following intraoperative reduction under general anesthesia in patients with cervical facet fracture and dislocation. Methods : Twenty-three patients with single level cervical facet fracture and dislocation who were subjected to the anterior approach alone following immediate intraoperative reduction under general anesthesia from March 2013 to December 2017 were enrolled in this study. Neurological status, clinical outcome, and radiological studies were evaluated preoperatively, postoperatively, and during the follow-up period. Results : The cohort comprised 15 men and eight women with a mean age of 57 years (from 24 to 81). All patients were operated on within the first 8 hours following the injury. After gentle manual reduction or closed reduction with Gardner-Wells traction, under general anesthesia monitored by somatosensory-evoked potentials, all operations were successfully completed using the anterior approach alone except in two patients, who had a risk of over-distraction. In them, a satisfactory gentle manual reduction or closed reduction was not possible, and required open posterior reduction of the locked facets followed by anterior cervical discectomy and fusion. In one patient, screw retropulsion was observed in 1 month after surgery. There were no reduction-related complications or neurological aggravations after surgery. All patients showed evidence of stability at the instrumented level at the final follow-up (mean follow-up, 12 months). Conclusion : Anterior approach following intraoperative reduction monitored by somatosensory-evoked potentials under general anesthesia for cervical dislocation and locked facets is a relatively safe and effective alternative when cervical alignment is achieved by intraoperative reduction.

• 대한화학회지
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• 제37권8호
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• pp.735-743
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• 1993

Cofacial bis-cobalt tetraphenylporphyrin(Co-TPP) 유도체 화합물들이 수식된 유리질 탄소 전극과 carbon microelectrode을 작업 전극으로 사용하여 여러가지 pH 용액에서 순환 전압전류법 및 시간 전류법에 의해 산소의 환원반응을 조사하였다. 산성용액에서 monomer인 cobalt tetraphenylporphyrin 화합물이 수식된 전극에서 산소의 환원반응경로는 중간 생성물인 H$_2$O$_2$로 가는 2전자 반응으로, dimer인 cofacial bis-cobalt tetraphenylporphyrin 유도체 화합물들이 수식된 전극에서는 최종 생성물인 H$_2$O로 가는 4전자 반응으로 진행되었다. 이와 같은 산소의 환원반응은 전체적으로 비가역적이며 확산지배적인 반응으로 주어졌다. pH 변화에 따른 산소의 환원전위는 pH 13에서 pH 4 까지는 직선관계가 성립하였으나 강한 산성용액에서는 이들 관계가 성립하지 않았다. 산성용액에서 산소의 환원전위는 알몸 유리질 탄소전극에서 보다 monomer Co-TPP 화합물이 수식된 유리질 탄소전극에서는 400 mV만큼, dimer Co-TPP 화합물이 수식된 전극에서는 750 mV 만큼 더 양전위 방향으로 이동되었다.

• 한국염색가공학회지
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• 제25권1호
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• pp.1-6
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• 2013

Nowdays, the computational simulation of molecular energy potentials and the empirical evidence using electrochemical reduction/oxidation values are very significant factors to predict of molecule's energy potentials. The prepared chemosensor herein consists of spirolactam ring system in the structure, providing intra-structural change with metal cation binding. In this study, rhodamine 6G-Naphthaldehyde chemosensor was determined and compared with HOMO/LUMO energy levels by computational calculation and cyclic voltammogram method.