• Journal of Microbiology and Biotechnology
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• v.20 no.11
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• pp.1500-1505
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• 2010

The novel swine-origin influenza A/H1N1 virus (S-OIV) first detected in April 2009 has been identified to transmit from humans to humans directly and is the cause of the currently emerged pandemic. In this study, nucleotide and deduced amino acid sequences of the hemagglutinin (HA) and neuraminidase (NA) of the S-OIV and other influenza A viruses were analyzed through bioinformatic tools for phylogenetic analysis, genetic recombination, and point mutation to investigate the emergence and adaptation of the S-OIV in humans. The phylogenetic analysis showed that the HA comes from triple reassortant influenza A/H1N2 and the NA from Eurasian swine influenza A/H1N1, indicating that HA and NA descend from different lineages during the genesis of the S-OIV. Recombination analysis ified the possibility of occurrence of recombination in HA and NA, denoting the role of reassortment in the outbreak. Several conservative mutations were observed in the amino acid sequences of the HA and NA, and these mutated residues were identical in the S-OIV. The results reported herein suggest the notion that the recent pandemic is the result of reassortment of different genes from different lineages of two envelope proteins, HA and NA, which are responsible for the antigenic activity of the virus. This study further suggests that the adaptive capability of the S-OIV in humans is acquired by the unique mutations generated during emergence.

• Bulletin of the Korean Chemical Society
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• v.32 no.6
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• pp.1939-1944
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• 2011

The nucleophilic substitution reactions of bis(Y-aryl) chlorophosphates (1) with substituted anilines and deuterated anilines are investigated kinetically in acetonitrile at 35.0 $^{\circ}C$. The kinetic results of 1 are compared with those of Y-aryl phenyl chlorophosphates (2). The substrate 1 has one more identical substituent Y compared to substrate 2. The cross-interaction between Y and Y, due to additional substituent Y, is significant enough to result in the change of the sign of cross-interaction constant (CIC) from negative ${\rho}_{XY}$ = -1.31 (2) to positive ${\rho}_{XY}$ = +1.91 (1), indicating the change of reaction mechanism from a concerted $S_N2$ (2) to a stepwise mechanism with a rate-limiting leaving group departure from the intermediate (1). The deuterium kinetic isotope effects (DKIEs) involving deuterated anilines ($XC_6H_4ND_2$) show secondary inverse, $k_H/k_D$ = 0.61-0.87. The DKIEs invariably increase as substituent X changes from electron-donating to electron-withdrawing, while invariably decrease as substituent Y changes from electron-donating to electron-withdrawing. A stepwise mechanism with a rate-limiting bond breaking involving a predominant backside attack is proposed on the basis of positive sign of ${\rho}_{XY}$ and secondary inverse DKIEs.

• Bulletin of the Korean Chemical Society
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• v.33 no.3
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• pp.1037-1041
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• 2012

The nucleophilic substitution reactions of (2R,4R,5S)-(+)-2-chloro-3,4-dimethyl-5-phenyl-1,3,2-oxazaphospholidine 2-sulfide (3) with substituted anilines ($XC_6H_4NH_2$) and deuterated anilines ($XC_6H_4ND_2$) are investigated kinetically in acetonitrile at $5.0^{\circ}C$. The anilinolysis rate of 3 involving a cyclic five-membered ring is considerably fast because of small negative value of the entropy of activation (${\Delta}S^\neq=-2cal\;mol^{-1}\;K^{-1}$) over considerably unfavorable enthalpy of activation (${\Delta}H^\neq=18.0\;kcal\;mol^{-1}$). Great enthalpy and small negative entropy of activation are ascribed to sterically congested transition state (TS) and bulk solvent structure breaking in the TS. A concerted $S_N2$ mechanism with a backside nucleophilic attack is proposed on the basis of the secondary inverse deuterium kinetic isotope effects, $k_H/k_D$ < 1.

• Journal of the Korean Society of Safety
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• v.16 no.1
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• pp.31-36
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• 2001

Surface crack growth characteristics and influence of the stress amplitude in rotary bending fatigue test were evaluated for annealed S35C steel, and than fractal dimensions of fatigue crack paths estimated using the box counting method. The following results that will be helpful to understand the fatigue crack growth mechanism were obtained. (1) Crack growth rate ds/dN and db/dN (s : half crack length at the surface crack, b : crack depth) depended on stress amplitude (${\Delta}{\sigma}/2$), stress intensity factor range (${\Delta}K_A, {\Delta}K_C$) and crack length. (2) At the effect area of 0.3 mm hole notch (s＜0.5 mm) crack growth rate did not depend on these factors. (3) The fractal dimensions (D) increased with stress amplitude (${\Delta}{\sigma}/2$) but decreased with cyclic number.

• Journal of the Korean Chemical Society
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• v.48 no.5
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• pp.461-466
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• 2004

Kinetics for the nucleophiles have been studied under high vacuum and high pressures in various temperatures. Pseudo-first order rate constants, second order rate constants, thermodynamic parameters and Hammett ${\rho}$-values are determined. The values of ${\Delta}V^{\neq},\;{\Delta}{\beta}^{\neq}\;and\;{\Delta}S^{\neq}$are all negative. The Hammett r-values are negative for the nucleophile (${\rho}$x) over the pressure range studied. The results of kinetic studies for pressure and nucleophilet show that these reactions proceed in typical $S_N2$ reaction mechanism and change of mechanism.

• Bulletin of the Korean Chemical Society
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• v.24 no.3
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• pp.306-310
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• 2003

Hydrolysis reactions of S-phenyl-S-vinyl-N-p-tosylsulfilimine (VSI) and its derivatives at various pH have been investigated kinetically. The hydrolysis reactions produced phenylvinylsulfoxide and p-toluene sulfonamide as the products. The reactions are first order and Hammett ρ values for pH 1.0, 6.0, and 11.0 are 0.82, 0.45, and 0.57, respectively. This reaction is not catalyzed by general base. The plot of k vs pH shows that there are three different regions of the rate constants $(k_t)$ in the profile.; At pH < 2 and pH > 10, the rate constants are directly proportional to the concentrations of hydronium and hydroxide ion catalyzed reactions, respectively. The rate constant remains nearly the same at 2 < pH < 10. On the bases of these results, the plausible hydrolysis mechanism and a rate equation have been proposed: At pH < 2.0, the reaction proceeds via the addition of water molecule to sulfur after protonation at the nitrogen atom of the sulfilimine, whereas at pH > 10.0, the reaction proceeds by the addition of hydroxide ion to sulfur directly. In the range of pH 2.0-10.0, the addition of water to sulfur of sulfilimine appears to be the rate controlling step.

• Journal of The Korean Astronomical Society
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• v.11 no.1
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• pp.31-36
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• 1978

Although Serkowski used a single value K=1.15 in representing all the observed interstellar linear polarization curves by his empirical relation $p({\lambda})/P_{max}$=exp (-K $1n^2({\lambda}_{max}/{\lambda})$), where $p_{max}$ is the maximum polarization at wavelength ${\lambda}_{max}$, we have noticed a meaningful variation in K from observations of 72 stars. By comparing K's with $P_{max}/E_{B-V}\;and\;with\;{\lambda}_{max}$, we have examined how the shape of the polarization curve is related with the degree of grain alignment on one hand, and with grain sizes on the other. We have shown that correlations between K, $P_{max}/E_{B-V}\;and\;with\;{\lambda}_{max}$, are consistent with the idea of Davis-Greenstein mechanism for grain alignment.

• The Journal of Internal Korean Medicine
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• v.22 no.2
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• pp.119-125
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• 2001

Objectives : This study was conducted to evaluate the effect and mechanism of Geupoongjibo-dan's relaxation of the tension of the blood vessel caused by Phenylephrine and KCI. Methods : In order to study the effect of Geupoongjibo-dan's relaxation of the blood vessel tension, Geupoongjibo-dan extract was infused into Phenylephrine and KCI-induced contracted rabbit aorta strips. To analyze the mechanism of Geupoongjibo-dan's effect on the blood vessel, Geupoongjibo-dan extract infused into Phenylephrine and KCI-induced contracted strips induced by agonists after treatment of N${\omega}$-nitro-L-arginine, Methylene Blue. Results : 1. Geupoongjibo-dan was very effective in relaxing the blood vessels contracted by Phenylephrine. 2. Geupoongjibo-dan was effective against Phenylephrine, than against KCI. 3. Geupoongjibo-dan's more relaxation effect on a blood vessel was terminated by N${\omega}$-nitro-L-arginine and methylene treatment. Conclusion : THis study showed that Geupoongjibo-dan's relaxation effect on a blood vessel is irrelevant to ${\alpha}$-adrenalin receptor, and it relaxes contracted vessels through cGMP channel.

• Journal of Veterinary Science
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• v.25 no.2
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• pp.30.1-30.16
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• 2024

Background: Biofilms, such as those from Staphylococcus epidermidis, are generally insensitive to traditional antimicrobial agents, making it difficult to inhibit their formation. Although quercetin has excellent antibiofilm effects, its clinical applications are limited by the lack of sustained and targeted release at the site of S. epidermidis infection. Objectives: Polyethylene glycol-quercetin nanoparticles (PQ-NPs)-loaded gelatin-N,O-carboxymethyl chitosan (N,O-CMCS) composite nanogels were prepared and assessed for the on-demand release potential for reducing S. epidermidis biofilm formation. Methods: The formation mechanism, physicochemical characterization, and antibiofilm activity of PQ-nanogels against S. epidermidis were studied. Results: Physicochemical characterization confirmed that PQ-nanogels had been prepared by the electrostatic interactions between gelatin and N,O-CMCS with sodium tripolyphosphate. The PQ-nanogels exhibited obvious pH and gelatinase-responsive to achieve on-demand release in the micro-environment (pH 5.5 and gelatinase) of S. epidermidis. In addition, PQ-nanogels had excellent antibiofilm activity, and the potential antibiofilm mechanism may enhance its antibiofilm activity by reducing its relative biofilm formation, surface hydrophobicity, exopolysaccharides production, and eDNA production. Conclusions: This study will guide the development of the dual responsiveness (pH and gelatinase) of nanogels to achieve on-demand release for reducing S. epidermidis biofilm formation.

• Transactions of Materials Processing
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• v.18 no.7
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• pp.544-549
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• 2009

This study aimed to elucidate the deformation mechanism during low-temperature superplasticity of fine-grained Ti-6Al-2Sn-4Zr-2Mo-0.1Si alloy in the context of constitutive equation. For this purpose, initial coarse equiaxed microstructure was refined to $2.2{\mu}m$ via dynamic globularization. Globularized microstructure exhibited large superplastic elongations(434-826%) at temperatures of $650-750^{\circ}C$ and strain rate of $10^{-4}s^{-1}$. It was found that the main deformation mechanism of fine-grained material was grain boundary sliding accommodated by dislocation motion with both stress exponent (n) and grain size exponent (p) values of 2. When the alpha grain size, not sub-grain size, was considered to be an effective grain size, the apparent activation energy for low-temperature superplasticity of the present alloy(169kJ/mol) was closed to that of Ti-6Al-4V alloy(160kJ/mol).