• Journal of Microbiology and Biotechnology
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• 제20권2호
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• pp.294-300
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• 2010

The Iro protein is a member of the HiPIP family with the [$Fe_4S_4$] cluster for electron transfer. Many reports proposed that the conserved aromatic residues might be responsible for the stability of the iron-sulfur cluster in HiPIP. In this study, Tyr10 was found to be a critical residue for the stability of the [$Fe_4S_4$] cluster, according to site-directed mutagenesis results. Tyr10, Phe26, and Phe48 were essential for the stability of the [$Fe_4S_4$] cluster under acidic condition. Trp44 was not involved in the stability of the [$Fe_4S_4$] cluster. Molecular structure modeling for the mutant Tyr10 proteins revealed that the aromatic group of Tyr10 may form a hydrophobic barrier to protect the [$Fe_4S_4$] cluster from solvent.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 하계종합학술대회 논문집(2)
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• pp.21-24
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• 2001

We studied aluminum cluster deposition using molecular dynamics simulation. We investigated the variations of the cluster momentum and the impulse force during collisions, and found that the close-packed cluster impact has some of properties of the single particle collision and the linear chain collisions. We also simulated the series of energetic cluster deposition with energy Per atom. When energy Per atom in cluster has some eV rather than very low, the intermixing occurred easily in growth film and we can obtain a good film without subsequent annealing process.

• Journal of Microbiology
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• 제34권2호
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• pp.105-116
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• 1996

Of actinomycetes isolated from volcanic compost soils, 115 representative strains which showed distinctive morphologicla features were numerically classified, compared with reference strains of Streptomyces. One hundred and twenty unit characters were tested and the average probability of error was 4.27%. The cluster analysis resulted in two groups: group A included strains of actinomycetes except streptomycetes. Group A was divided into 2 major clusters (over 5 strains), 10-diaminopimelic acid. Group B was divided into 5 clusters, of which 4 clusters contained mesodiminopimelic acid and 1 cluster LL-diaminopimelic acid. The major clusters of group A showed higher abilities of substrate utilization and degradation, and higher resistance to inhibitors, whereas the minor and single member clusters of group A showed relatively higher antimicrobial activities. On the other hand, all clusters of group B showed relatively lower abilities of substrate utilization and degradation and lower resistance to inhibitors.

• Transactions on Electrical and Electronic Materials
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• 제4권1호
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• pp.1-6
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• 2003

We have studied the size confinement effect on the properties of melting-like transition of small icosahedral copper clusters using a classical molecular dynamics simulation based on a well fitted empirical potential. We investigated the caloric curves of icosahedron nanoclusters and the significant depression in the melting temperatures of the copper nanoclusters was compared with that of the bulk copper. A structural transitions from decahedral to icosahedral shapes were shown. As the cluster size increased, the melting temperature increased, and the latent heat increased but seem to be saturated. However, the specific heat was unrelated to the cluster size.

• 한국산학기술학회:학술대회논문집
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• 한국산학기술학회 2011년도 춘계학술논문집 1부
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• pp.306-309
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• 2011

A lattice model based molecular clusters is presented to improve a classical equation of state(EOS) for volumetric properties in the critical region. The term is based on the two assumptions: (1) The Helmholtz energy is individually divided into classical and long-range density fluctuation contribution (2) All molecules form cluster near the critical region due to long-range density fluctuation. To formulate such molecular cluster, we extended the Veytsman statistics originally developed for the cluster due to hydrogen bonding. The probability function in the statistics is modified to represent the characteristics of long-range density fluctuation vanishing far from critical region. The proposed fluctuation contribution was incorporated into the Sanchez-Lacombe EOS and the combined model with 6 adjustable parameters has been tested against experimental VLE data for pure compounds. The combined model is found to well represent flatten critical isotherm for methane and top of the coexistence curve for the tested components.

• Bulletin of the Korean Chemical Society
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• 제13권5호
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• pp.482-486
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• 1992

Ion-molecule reactions of acetylene and mixed acetylene-ammonia cluster ions are studied using an electron impact time-of-flight mass spectrometer. The present results clearly demonstrate that $(C_2H_2)_n^+$ cluster ion distribution represents a distinct magic number of n=3. The mass spectroscopic evidence for the enhanced structural stabilities of $[C_6H_4{\cdot}(NH_3)_m]^+$ (m=0-8) ions is also found along with the detection of mixed cluster $[(C_2H_2)_n{\cdot}(NH_3)_m]^+$ ions, which gives insight into the feasible structure of solvated ions. This is rationalized on the basis of the structural stability for acetylene clusters and the dissociation dynamics of the complex ion under the presence of solvent molecules.

• Bulletin of the Korean Chemical Society
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• 제24권6호
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• pp.771-776
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• 2003

The structural and dynamic properties of small n-alkane clusters embedded in a mesoscopic solvent are investigated. The solvent interactions are taken into account through a multi-particle collision operator that conserves mass, momentum and energy and the solvent dynamics is updated at discrete time intervals. The cluster molecules interact among themselves and with the solvent molecules through intermolecular forces. The properties of n-heptane and n-decane clusters interacting with the mesoscopic solvent molecules through repulsive Lennard-Jones interactions are studied as a function of the number of the mesoscopic solvent molecules. Modifications of both the cluster and solvent structure as a result of cluster-solvent interactions are considered. The cluster-solvent interactions also affect the dynamics of the small n-alkane clusters.

• Journal of Microbiology and Biotechnology
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• 제18권12호
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• pp.1890-1894
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• 2008

Apoemulsan is a biopolymer with potent emulsification activity, produced by Acinetobacter venetian us RAG-1 (RAG-1). The wee gene cluster is responsible for apoemulsan biosynthesis. The analysis of (i) a putative polysaccharide copolymerase mutant (${\Delta}wzc$), (ii) a putative polymerase mutant (${\Delta}wzy$), and (iii) an apoemulsan-deficient variant (${\Delta}2$) indicated that the wee gene cluster controls the synthesis of two polysaccharides: high molecular weight (HMW) and low molecular weight (LMW). LMW polysaccharide of wee origin was present in LPS isolated from RAG-1 cells, suggesting a link to the Lipid A-core of LPS molecules. SDS-PAGE analysis indicated that apoemulsan is copurified with LPS polysaccharide, with implications in the emulsification activity of RAG-1 polymer.

• Bulletin of the Korean Chemical Society
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• 제16권3호
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• pp.238-243
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• 1995

A pulsed molecular beam source having short pulse duration (typically 70 ${\mu}s)$ and narrow velocity distribution (${\Delta}$v/v=8% for helium) has been costructed utilizing a commercial fuel injector. Beam characteristics of helium and ammonia seeded in helium expansions are accomplished by the use of an electron impact time-or-flight mass spectrometer. The comparisons between experimental data and theoretical calculations show that the proper beam speed is important to predict the evolution of stream temperature and valve shutter function. The decreasing tendency of pulse duration with increasing cluster size leads to the conclusion that the cluster beam property is described as a function of cluster mass and disinct cluster temperature.

• Journal of Microbiology and Biotechnology
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• 제15권5호
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• pp.1120-1124
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• 2005

Pseudomonas putida KCTC 1639 was newly identified as a potential producer of biodegradable medium chain length polyhydroxyalkanoates. It exhibited a carbon assimilation pattern quite different from other known P. putida strains, but a more similar pattern with P. oleovorans, which assimilates the carbon sources mainly through ${\beta}$-oxidation rather than the fatty acid biosynthesis pathway. The PHA synthesis gene cluster from P. putida KCTC1639 was composed of two gene loci; the PHA synthase gene locus and granule-associated gene locus, which were cloned and deposited in the GenBank under accession numbers AY286491 and AY750858 as a new nucleotide sequence, respectively. The molecular structure and amino acid homology of the new gene cluster were compared with those from Pseudomonas species, including other P. putida strains and P. oleovorans, and a higher than $90\%$ homology was observed.