• Bulletin of the Korean Chemical Society
• /
• v.15 no.8
• /
• pp.669-673
• /
• 1994

Coordination isomers of cis-(N-N)Pt(Glu) prepared by reaction of cis-(N-N)Pt($SO_4$) (N-N=2$NH_3$, ethylenediamine(en),(R,R)-1,2-diaminocyclohexane (DACH), N,N,N',N'-tetramethylethylenediamine (TMEDA)) with barium glutamate in water have been monitored and characterized by $^1H-NMR$, $^{13}C-NMR$, IR, and mass spectra. The reaction at room temperature affords the mixture of O,O'-and N, ${\alpha}$ O-chelated platinum(II) complexes. The O,O'-chelate initially formed isomerized to N,${\alpha}$O-chelate on standing for a long time or increasing temperature. The ratio of the two isomers at room temperature depends on the nature of the nitrogen donor coligand (N-N).

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.15 no.7
• /
• pp.591-596
• /
• 2002

In this work, epitaxial GaN is grown on sapphire substrate in AlGaN/GaN heterostructures. Deliberate oxygen doping of GaN grown by MOVPE has been studied. The electron concentration increased as a function of the square root of the oxygen partial Pressure. Oxygen is a shallow donor with a thermal ionization energy of $27\pm2 meV$ measured by temperature dependent Hall effects. A compensation ratio of $\theta$=0.3~0.4 was determined from Hall effect measurements. The formation energy of $O_N$ of $E^F$ =1.3eV determined from the experimental data, is lower than the theoretically predicted vague.

• Journal of Korean Society of Environmental Engineers
• /
• v.28 no.3
• /
• pp.292-299
• /
• 2006

Batch experiments were performed to evaluate the effects of the electron donor dosage and the initial biomass on the reductive dechlorination of perchloroethene(PCE) with benzoate as an electron donor. When benzoate was added less than the theoretical requirement for dechlorination(electron donor/acceptor ratio=0.5 and 1), the dechlorination efficiency increased from 71% to 94.3% with the increase in benzoate dosage, but the fraction of electron equivalent utilized for dechlorination decreased from 92.7% to 79.6%. Methane production was observed when the hydrogen concentration was higher than the threshold value(10 nM) after PCE and trichloroethene (TCE) were reduced to cis-1,2-dichloroethene(cDCE). When benzoate was added more than the theoretical requirement, the residual hydrogen converted into methane after the completion of dechlorination. The increase in the seeding biomass shortened the lag time for dechlorination, but it did not affect the maximum dechlorination rate as it was mainly governed by the benzoate fermentation rate. When the seeding biomass concentration was high, active dechlorination during the early period increased dechlorination efficiency while decreasing methane production.

• Journal of Microbiology and Biotechnology
• /
• v.30 no.9
• /
• pp.1436-1442
• /
• 2020

Amylosucrase (ASase, E.C. 2.4.1.4) is capable of efficient glucose transfer from sucrose, acting as the sole donor molecule, to various functional acceptor compounds, such as polyphenols and flavonoids. An ASase variant from Deinococcus geothermalis, in which the 226^th alanine is replaced with asparagine (DgAS-A226N), shows increased polymerization activity due to changes in the flexibility of the loop near the active site. In this study, we further investigated how the mutation modulates the enzymatic activity of DgAS using molecular dynamics and docking simulations to evaluate interactions between the enzyme and phenolic compounds. The computational analysis revealed that the A226N mutation could induce and stabilize structural changes near the substrate-binding site to increase glucose transfer efficiency to phenolic compounds. Kinetic parameters of DgAS-A226N and WT DgAS were determined with sucrose and 4-methylumbelliferone (MU) as donor and acceptor molecules, respectively. The k_cat/K_m value of DgAS-A226N with MU (6.352 mM^-1min^-1) was significantly higher than that of DgAS (5.296 mM^-1min^-1). The enzymatic activity was tested with a small phenolic compound, hydroquinone, and there was a 1.4-fold increase in α-arbutin production. From the results of the study, it was concluded that DgAS-A226N has improved acceptor specificity toward small phenolic compounds by way of stabilizing the active conformation of these compounds.

• Environmental Engineering Research
• /
• v.16 no.4
• /
• pp.213-218
• /
• 2011

The two-stage intermittent aeration activated sludge process (IAP) and dynamic-flow intermittent aeration activated sludge process (DFP) were investigated for the nutrient removal of domestic wastewater. Three sets of IAP and one set of DFP were operated. The fermented settled sludge taken from the primary settling tank was added to two IAP and one DFP as an external electron donor, with one IAP, in which an external carbon source was not added, as a control. All the systems were operated at a sludge retention time of 20 days and a hydraulic retention time of 12 hr. A Higher denitrification rate was observed with the fermented settled sludge for the denitrification compared to the process without the addition of the organic source. The result indicates that the fermented acid from the primary domestic sludge has been proved to be an excellent electron donor for denitrification and biological phosphorus removal with IAP and DFP in treating relatively low C/N ratio(Carbon / Nitrogen ratio) wastewater. Phosphate accumulating organisms have a capability of competing with denitrifiers in the presence of volatile organic acids under anoxic conditions.

• BMB Reports
• /
• v.46 no.1
• /
• pp.37-40
• /
• 2013

CY-007 and CY-049 pteridine glycosyltransferases (PGTs) that differ in sugar donor specificity to catalyze either glucose or xylose transfer to tetrahydrobiopterin were studied here to uncover the structural determinants necessary for the specificity. The importance of the C-terminal domain and its residues 218 and 258 that are different between the two PGTs was assessed via structure-guided domain swapping or single and dual amino acid substitutions. Catalytic activity and selectivity were altered in all the mutants (2 chimeric and 6 substitution) to accept both UDP-glucose and UDP-xylose. In addition, the wild type activities were improved 1.6-4.2 fold in 4 substitution mutants and activity was observed towards another substrate UDP-N-acetylglucosamine in all the substitution mutants from CY-007 PGT. The results strongly support essential role of the C-terminal domain and the two residues for catalysis as well as sugar donor specificity, bringing insight into the structural features of the PGTs.

• Asian-Australasian Journal of Animal Sciences
• /
• v.8 no.4
• /
• pp.321-323
• /
• 1995

Observations were recorded regarding various fertility parameters on 26 Jersey donor cows following superovulation under tropical conditions. These cows, in their mid-luteal phase were treated with 2,500-3,000 i.u. PMSG or 28-40 mg FSH followed by $500{\mu}g$ $PGF_{2{\alpha}}$ injection 48-60 hours later, to induce oestrus. The cows were bred artificially twelve hours following standing oestrus. Embryo collection was carried out 7 days after oestrus. $PGF_{2{\alpha}}$ was injected to each donor cow after embryo recovery to regress the corpora lutea. Fertility data($PGF_{2{\alpha}}$-Oestrus interval, services per conception, days between embryo collection and successful service and any pathololgical condition) were recorded. $PGF_{2{\alpha}}$-Oestrus interval and correlation (r) between number of corpora lutea and $PGF_{2{\alpha}}$-Oestrus interval were $30.9{\pm}6.3$ and 0.17, respectively. Of 26 treated donors, 19 conceived within a period of $91.7{\pm}18.8$ days after embryo recovery. Average services per conception were $2.3{\pm}0.3$. Only two cows developed metritis which conceived after treatment with antibiotics. These observations indicated no profound adverse effect of superovulation on subsequent reproduction of donor cows, except some effect on services per conception, under tropical conditions.

• Journal of Microbiology
• /
• v.35 no.3
• /
• pp.206-212
• /
• 1997

Heliobacillus mobilis is a strictly anaerobic Gram-positive bacterium which contains a primitive Photosystem I-type reaction center. The membrane-bound cytochrome $C_{553}$ from the heliobacterium suggested to be the immediate electron donor to the photooxidized pigment (P798+) has been isolated and characterized. The heme protein was visualized as a major component with an apparent molecular size of 17kDa in TMBZ-staining analysis of the membrane preparation and showed characteristic $\alpha$ (552.5 nm), $\beta$ (522nm), and Soret absorption (416 nm) peaks of a typical reduced c-type cytochrome in the partially purified sample. The internal 43 amino acid sequence of the electron donor was obtained by chemical agent and protease treatments followed by N-terminal sequencing of the resulting fragments. The internal sequence carries lots of lysine residues and a Cys-X-X-Cys-His sequence motif which are the characteristics of typical c-type cytochromes. The analysis of the sequence by FAST or FASTA program, however, did not show any significant similarity to other known heme proteins.

• Bulletin of the Korean Chemical Society
• /
• v.28 no.12
• /
• pp.2369-2376
• /
• 2007

N2O has been found from experimental and theoretical considerations to bind on-top to the Pd(110) surface in a tilted end-on fashion via its terminal N atom. We use a frontier orbital description of the bonding interactions in the Pd-N2O system to obtain molecular insight into the catalytic mechanism of the activation of N2O by the Pd(110) surface giving rise to the formation of N2 and O on the surface. For the tilted end-on N2O binding mode, the LUMO 3π of N2O has good overlap with the Pd dσ and dπ orbitals which can serve as the electron donors. The donor-acceptor orbital overlap is favorable for electron transfer from Pd to N2O and is expected to dominate the surface reaction pathway of N2O decomposition.

• Journal of the Korean Vacuum Society
• /
• v.6 no.4
• /
• pp.343-347
• /
• 1997

The dependence of compensation mechanism in $P^+$-InGaAs layer implanted with oxygen on the annealing temperatures was investigated. The oxygen implantation was performed for electrical isolation. The conductivity was controlled by damage related traps below $500^{\circ}C$. For the temperature of 500 to $600^{\circ}C$, oxygen began to show the chemical effect of compensating the acceptors due to activation and type conversion (plongrightarrown-type) occurred at $600^{\circ}C$. This indicates that the defects generated by the chemical activity of oxygen increased with increasing annealing temperature, where activation energy of 24.2 meV was obtained. It is attributed to the formation of native defects, such as In interstitials, acting as shallow donor in InGaAs. Above $600^{\circ}C$, the interstitial Be atoms become reactivated and the n-type conductivity decreases.