• Journal of the Korean Chemical Society
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• v.19 no.2
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• pp.123-129
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• 1975

The rate constants of the hydrolysis of phenylvinylsulfone were determined by ultraviolet spectrophotometry at various pH and a rate equation which can be applied over wide pH range was obtained. The reaction mechanism of hydrolysis of phenylvinylsulfone and especially the catalytic contribution of hydroxide ion which did not study carefully before in acidic media, can be fully explained by the rate equation obtained. The rate equation reveals that: below pH 7, the reaction is initiated by the addition of water molecule to phenylvinylsulfone. At above pH 9, the overall rate constant is only dependent upon the concentration of hydroxide ion.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.87.1-87.1
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• 2017

High functional catalyst to efficiently produce clean and earth-abundant renewable fuels plays a key role in securing energy sustainability and environmental protection of our society. Hydrogen has been considered as one of the most promising energy carrier as represented by focused research works on developing catalysts for the hydrogen evolution reaction (HER) from the water hydrolysis over the last several decades. So far, however, the major catalysts are expensive transition metals. Here using first principles density functional theory (DFT) calculations we screen various pyrites for HER by identifying fundamental descriptor governing the catalytic activity. We enable to capture a strong linearity between experimentally measured exchange current density in HER and calculated adsorption energy of hydrogen atom in the pyrites. The correlation implies that there is an underlying design principle tuning the catalytic activity of HER.

• Journal of Microbiology and Biotechnology
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• v.8 no.4
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• pp.318-324
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• 1998

A ${\beta}$-galactosidase with high transgalactosylic activity was purified from a Bacillus species, registered as KFCC10855. The enzyme preparation showed a single protein band corresponding to a molecular mass of 150 kDa on SDS-PAGE and gave a single peak with the estimated molecular mass of 250 kDa on Sephacryl S-300 gel filtration, suggesting that the enzyme is a homodimeric protein. The amino acid and sugar analyses revealed that the enzyme is a glycoprotein, containing 19.2 weight percent of sugar moieties, and is much more abundant in hydrophilic amino acid residues than in hydrophobic residues, the mole ratio being about 2:1. The pI and optimum pH were determined to be 5.0 and 6.0, respectively. Having a temperature optimum at $70^{\circ}C$ for the hydrolysis of lactose, the enzyme showed good thermal stability. The activity of the enzyme preparation was markedly increased by the presence of exogenous Mg (II) and was decreased by the addition of EDTA. Among the metal ions examined, the most severely inhibitory effect was seen with Ag (I) and Hg (II). Further, results of protein modification by various chemical reagents implied that 1 cysteine, 1 histidine, and 2 methionine residues occur in certain critical sites of the enzyme, most likely including the active site. Enzyme kinetic parameters, measured for both hydrolysis and transgalactosylation of lactose, indicated that the enzyme has an excellent catalytic efficiency for formation of the transgalactosylic products in reaction mixtures containing high concentrations of the substrate.

• Applied Chemistry for Engineering
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• v.26 no.6
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• pp.743-745
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• 2015

Amorphous cobalt phosphates were synthesized with their distinct morphology by controlling the amount of base in the synthetic condition. The crystallinity and morphology of cobalt phosphates were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The prepared cobalt phosphates were applied as a heterogeneous catalyst for generating hydrogen gas from the hydrolysis reaction of sodium borohydride. We found that the catalyst prepared using the least amount of base condition at room temperature showed a plate shape with less than 10 nm thickness, which resulted in the best catalytic activity among all catalysts due to the large surface area.

• Journal of the Korean Applied Science and Technology
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• v.32 no.1
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• pp.165-169
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• 2015

N-propyl-N,N-dimethylethanolamine was directly ultrasonicated in acidic water for 6 minute to give clear stock solutions. The catalytic hydrolysis of N-propyl-N,N-dimethylethanolamine was studied at $30{\sim}55^{\circ}C$ in the presence of uni-lamellar vesicle and mixture of uni- and multi-lamellar aggregates. The difference of rate between uni- and mixture was observed, where uni-lamellar reaction was more catalytic effect. The phase transition temperature of vesicle was $37{\sim}44^{\circ}C$. The particle size of multi-lamellar than that of uni-lamellar of biological membrane was measured more largely.

• Journal of Microbiology and Biotechnology
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• v.2 no.1
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• pp.56-65
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• 1992

The complete nucleotide sequence of the Bacillus circulans F-2 RSDA gene, coding for raw starch digesting a-amylase (RSDA), has been determined. The RSDA structure gene consists of an open reading frame of 2508 bp. Six bp upstream of the translational start codon of the RSDA is a typical gram-positive Shine-Dalgarno sequence and the RSDA encodes a preprotein of 836 amino acids with an Mr of 96, 727. The gene was expressed from its own regulatory region in E. coli and two putative consensus promoter sequences were identified upstream of a ribosome binding site and an ATG start codon. Confirmation of the nucleotide sequence was obtained and the signal peptide cleavage site was identified by comparing the predicted amino acid sequence with that derived by N-terminal analysis of the purified RSDA. The deduced N-terminal region of the RSDA conforms to the general pattern for the signal peptides of secreted prokaryotic proteins. The complete amino acid sequence was deduced and homology with other enzymes was compared. The results suggested that the Thr-Ser-rich hinge region and the non-catalytic domain are necessary for efficient adsorption onto raw substrates, and the catalytic domain (60 kDa) is necessary for the hydrolysis of substrates, as suggested in previous studies (8, 9).

• Applied Biological Chemistry
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• v.48 no.4
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• pp.326-330
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• 2005

In the catalytic hydrolysis of 2',3'-cAMP by the Cu(II) complexes of 2,9-(N,N-dimethylethylenediamino)-1,10-phenanthroline (A) and 2,9-(N,N-dimethylethylenediaminomethyl)-1,10-phenanthroline (B) that are designed as a new ligand molecule of artificial DNase, due to the four intramolecular H-bonds forming between amino groups of ligand molecule and phosphoryl group of 2',3'-cAMP. It is anticipated that Cu(II) complexes of (A) and (B) are able to promote a rate that is as much as seventy thousand times faster than the catalytic hydrolysis rate of 2',3'-cAMP by Cu(II) complexes of 2,9-dimethyl-o-phenanthroline.

• Transactions of the Korean hydrogen and new energy society
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• v.33 no.4
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• pp.343-352
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• 2022

Co/Al₂O₃ nanopowder was used as a catalyst to investigate the effect of catalyst support, reduction temperature, sodium borohydride (NaBH₄) concentration, sodium hydroxide (NaOH) concentration, and reaction temperature on the characteristics of NaBH₄ hydrolysis. The Co/Al₂O₃ nanopowder showed a high catalytic activity among various catalysts. Catalyst reduction at 250℃ exhibited a relatively good activity. The activity decreased with an increase in the NaBH₄ concentration. Conversely, the activity increased and then decreased with an increase in the NaOH concentration. Additionally, the activity increased with an increase in the reaction temperature. The value of apparent activation energy was 40.81 kJ/mol, which was lower than the other Co-based catalysts. Thus, Co/Al₂O₃ nanopowder catalyst can be widely used for NaBH₄ hydrolysis owing to its superior catalytic activity.

• Bulletin of the Korean Chemical Society
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• v.24 no.1
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• pp.65-69
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• 2003

The kinetic and chemical mechanisms of AChE-catalyzed hydrolysis of short-chain thiocholine esters are relatively well documented. Up to propanoylthiocholine (PrTCh) the chemical mechanism is general acid-base catalysis by the active site catalytic triad. The chemical mechanism for the enzyme-catalyzed butyrylthiocholine(BuTCh) hydrolysis shifts to a parallel mechanism in which general base catalysis by E199 of direct water attack to the carbonyl carbon of the substrate. [Selwood, T., et al. J. Am. Chem. Soc. 1993, 115, 10477- 10482] The long chain thiocholine esters such as hexanoylthiocholine (HexTCh), heptanoylthiocholine (HepTCh), and octanoylthiocholine (OcTCh) are hydrolyzed by electric eel acetylcholinesterase (AChE). The kinetic parameters are determined to show that these compounds have a lower Michaelis constant than BuTCh and the pH-rate profile showed that the mechanism is similar to that of BuTCh hydrolysis. The solvent isotope effect and proton inventory of AChE-catalyzed hydrolysis of HexTCh showed that one proton transfer is involved in the transition state of the acylation stage. The relationship between the dipole moment and the Michaelis constant of the long chain thiocholine esters showed that the dipole moment is the most important factor for the binding of a substrate to the enzyme active site.

• Journal of the Korean Applied Science and Technology
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• v.34 no.4
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• pp.883-891
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• 2017

For the preferential oxidation of CO contained in the fuel of polymer electrolyte membrane fuel cell (PEMFC), CuO-$CeO_2$ mixed oxide catalysts were prepared by the sol-gel and co-precipitation methods to replace noble metal catalysts. In the catalyst preparation by the sol-gel method, Cu/Ce ratio and hydrolysis ratio were changed. The catalytic activity of the prepared catalysts was compared with the catalytic activity of the noble metal catalyst($Pt/{\gamma}-Al_2O_3$). Among the catalysts prepared with different Cu/Ce ratios, the catalyst whose Cu/Ce ratio was 4:16 showed the highest CO conversion (90%) and selectivity (60%) at $150^{\circ}C$. As the hydrolysis ratio was increased in the catalyst preparation, surface area increased, and catalytic activity also increased. The highest CO conversions with the CuO-$CeO_2$ mixed oxide catalyst prepared by the co-precipitation method and the noble metal catalyst (1wt% $Pt/{\gamma}-Al_2O_3$) were 82 and 81% at $150^{\circ}C$, respectively, whereas the highest CO conversion with the CuO-$CeO_2$ mixed oxide catalyst prepared by the sol-gel method was 90% at the same temperature. This indicates that the catalyst prepared by the sol-gel method shows higher catalytic activity than the catalysts prepared by the co-precipitation method and the noble metal catalyst. From the CO-TPD experiment, it was found that the catalyst having CO desorption peak at a lower temperature ($140^{\circ}C$) revealed higher catalytic activity.