• Bulletin of the Korean Chemical Society
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• v.28 no.12
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• pp.2261-2265
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• 2007

Prevention of thermal aggregation of the denatured protein by the group II chaperonin from the aerobic hyperthermophilic crenarchaeon Aeropyrum pernix K1 (ApcpnA) has been investigated. ApcpnA exists as a homo-oligomer in a ring structure, which protects thermal aggregation of the chemically denatured bovine rhodanese at 50 oC. ApcpnA alone is not sufficient for chaperonin activity, but the chaperonin activity is greatly enhanced in the presence of manganese ion and ATP. Compared to the mesophilic chaperonin GroEL/GroES, ApcpnA is more activated at a higher temperature and protects the aggregation-prone unfolded state of the denatured rhodanese from thermal aggregation. Binding of ATP is sufficient for ApcpnA to perform the chaperonin function in vitro, but hydrolysis of ATP is not necessarily required. We propose that utilization of Mn2+ and adenosine nucleotide regardless of ATP hydrolysis may be one of peculiar properties of archaeal chaperonins.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.7
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• pp.1715-1724
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• 2013

The maximum lifetime data aggregation problem is to maximize the network lifetime as minimizing the transmission energy of all deployed nodes in wireless sensor networks. In this paper, we propose a simulated annealing algorithm to solve efficiently the maximum lifetime data aggregation problem on the basis of meta-heuristic approach in wireless sensor networks. In order to make a search more efficient, we propose a novel neighborhood generating method and a repair function of the proposed algorithm. We compare the performance of the proposed algorithm with other existing algorithms through some experiments in terms of the network lifetime and algorithm computation time. Experimental results show that the proposed algorithm is efficient for the maximum lifetime data aggregation problem in wireless sensor networks.

• Journal of Institute of Control, Robotics and Systems
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• v.22 no.11
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• pp.984-990
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• 2016

In wireless mesh sensor networks (WMSNs), sensor nodes are connected in the form of a mesh topology and transfer sensor data by multi-hop routing. A data aggregation method for WMSNs is required to minimize the number of routing hops and the energy consumption of each node with limited battery power. This paper presents a shortest path data aggregation method for WMSNs. The proposed method utilizes a simple hash function based on shuffled row major indexing for addressing sensor nodes. This allows sensor data to be aggregated without complex routing tables and calculation for deciding the next hop. The proposed data aggregation algorithms work in a fractal fashion with different mesh sizes. The method repeatedly performs gathering and moves sensor data to sink nodes in higher-level clusters. The proposed method was implemented and simulations were performed to confirm the accuracy of the proposed algorithms.

• BMB Reports
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• v.40 no.5
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• pp.678-683
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• 2007

Extracts from the leaves of the Ginkgo biloba are becoming increasingly popular as a treatment that is claimed to reduce atherosclerosis, coronary artery disease, and thrombosis. In this study, the effect of ginkgolide B (GB) from Ginkgo biloba leaves in collagen (10 ${\mu}g/ml$)-stimulated platelet aggregation was investigated. It has been known that human platelets release matrix metallo-proteinase-9 (MMP-9), and that it significantly inhibited platelet aggregation stimulated by collagen. Zymographic analysis confirmed that pro-MMP-9 (92-kDa) was activated by GB to form an MMP-9 (86-kDa) on gelatinolytic activities. And then, activated MMP-9 by GB dose-dependently inhibited platelet aggregation, intracellular $Ca^{2+}$ mobilization, and thromboxane $A_2$ ($TXA_2$) formation in collagen-stimulated platelets. Activated MMP-9 by GB directly affects down-regulations of cyclooxygenase-1 (COX-1) or $TXA_2$ synthase in a cell free system. In addition, activated MMP-9 significantly increased the formation of cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP), which have the anti-platelet function in resting and collagen-stimulated platelets. Therefore, we suggest that activated MMP-9 by GB may increase the intracellular cAMP and cGMP production, inhibit the intracellular $Ca^{2+}$ mobilization and $TXA_2$ production, thereby leading to inhibition of platelet aggregation. These results strongly indicate that activated MMP-9 is a potent inhibitor of collagen-stimulated platelet aggregation. It may act a crucial role as a negative regulator during platelet activation.

• Journal of Pharmaceutical Investigation
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• v.31 no.1
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• pp.7-12
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• 2001

Amphotericin B (AmB) is a drug of choice for the treatment of systemic fungal diseases, but its use is considerably limited due to a high incidence of toxicity, particularly nephrotoxicity. It has been demonstrated that the toxicity of AmB is caused by self-aggregated species of the drug and that unaggregated (monomeric) drug is nontoxic but still expresses antifungal activity. Poly (ethylene oxide) (PEO) is a water-soluble polymer, which may impact the aggregation state of AmB. We have studied the aggregation state of AmB as a function of PEO molecular weight and concentration. At 3,000 and 8,000 g/mole, there was minimal or no change of critical aggregation concentration (CAC) of AmB regardless of the concentration of polymer. By contrast at 20,000 g/mole, the CAC of AmB strikingly increased to 24.3 and $37.5\;{\mu}M$ at 5.0% and 10 % w/v of polymer, respectively. The critical overlap concentration (COC) of PEO 20,000 g/mole was 5.5%. It appears that an interaction between monomeric AmB and polymer coil increases above the COC, competing with self-aggregation of the drug. Accordingly, the degree of aggregation of AmB stayed low and the toxicity became less. There was no such effect at 3,000 and 8,000 g/mole of PEO, owing perhaps to small dimensions in comparison to AmB. Based upon these findings, less toxic AmB formulation may be developed by a pharmaceutical technique such as solid dispersion system containing both AmB and PEO 20,000 g/mole.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.8
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• pp.873-876
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• 2012

Ionic liquids (ILs) existing in the liquid ion form under standard conditions show a unique properties. 1-10-Alkyl-3-methyl-imidazolium bromide ([C10mim][Br]) is one of the ILs that shows amphiphilic characteristics under specific conditions. This property enables it to function as a surfactant, and therefore, it finds applications in a wide range of areas. In this study, we tried to predict the behavior, especially the aggregation aspect, of [C10mim][Br] in an aqueous solution using molecular dynamics (MD) simulations. The canonical (NVT) ensemble was used to relax the system and trace the trajectory of atoms. Several case studies were simulated and the interaction among [C10mim]+, [Br]-, and water was analyzed using the radial distribution function of each atom. The density distribution function was also used for the structural analysis of the entire system. We used the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) code for the present MD simulations.

• Biomedical Science Letters
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• v.10 no.1
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• pp.1-8
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• 2004

Cordycepin separated from Cordyceps militaris is a major physiologic active component in Cordyceps militaris. The platelet aggregation is stimulated by $Ca^{2+}$, which is either mobilized from intracellular endoplasmic reticulum or transported from extracellular space. cGMP antagonizes the actions of $Ca^{2+}$. Based on these facts, we have investigated the effects of cordycepin on the mobilization of $Ca^{2+}$ and the production of cGMP on collagen ($10\mu$g/ml)-induced human platelet aggregation. Cordycepin potently stimulated the human platelet aggregation induced by collagen ($10\mu$g/ml) in a dose-dependent manner. Cordycepin (500 $\mu$M) inhibited also the collagen-induced human platelet aggregation in the presence both 1 mM and 2 mM of $CaCl_2$. These are in accord with the results that cordycepin inhibited the $Ca^{2+}$- influx on collagen-induced human platelet aggregation. These results suggest that cordycepin decrease the intracellular $Ca^{2+}$ concentration to inhibit collagen-induced human platelet aggregation. Besides, cordycepin increased the level of cGMP on collagen-induced human platelet aggregation. This result is related with the decrease of intracellular $Ca^{2+}$ concentration, because cGMP inhibits the mobilization of $Ca^{2+}$. In addition, cordycepin inhibited the human platelet aggregation induced by LY -83583, inhibitor of guanylate cyclase. This result suggested that cordycepin inhibit the platelet aggregation by stimulating the activity of guanylate cyclase. In conclusion, we demonstrated that cordycepin might have the antiplatelet function by inhibiting $Ca^{2+}$-mobilization via the stimulation of the production of cGMP.

• BMB Reports
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• v.39 no.3
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• pp.335-338
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• 2006

Methylglyoxal (MG) is an endogenous physiological metabolite which is present in increased concentrations in diabetics. MG reacts with the amino acids of proteins to form advanced glycation end products. In this in vitro study, we investigated the effect of MG on the structure and function of ceruloplasmin (CP) a serum oxidase carrier of copper ions in the human. When CP was incubated with MG, the protein showed increased electrophoretic mobility which represented the aggregates at a high concentration of MG (100 mM). MG-mediated CP aggregation led to the loss of enzymatic activity and the release of copper ions from the protein. Radical scavengers and copper ion chelators significantly prevented CP aggregation. CP is an important protein that circulates in plasma as a major copper transport protein. It is suggested that oxidative damage of CP by MG may induce perturbations of the copper transport system and subsequently lead to harmful intracellular condition. The proposed mechanism, in part, may provide an explanation for the deterioration of organs in the diabetic patient.

• Bulletin of the Korean Chemical Society
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• v.19 no.6
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• pp.650-654
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• 1998

Aggregations of 1,1'-diethyl-2,2'-carbocyanine iodide (DCI) and 1,1'-diethyl-2,2'-dicarbocyanine iodide (DDT) in aqueous solution have been investigated by the steady-state absorption spectroscopy. The equilibrium constants for dimerization of DCI and DDT are found to be $(9.8{\pm}0.5){\times}10^4 \;and\; (1.6{\pm}0.5){\times}10^5\; M^{-1}$, respectively, at 293 K. The enthalpy changes for the dimerization of DCI and DDT are -6.7±0.7 and -7.7±0.8 kcal/mol, respectively. The results show that the dispersion force plays an important role in the aggregation of DCI and DDT in aqueous solution. The absorption bandwidth of DCI/ethanol system has been measured as a function of temperature, providing the evidence for no strong interaction between DCI and solvent molecules. The participation of hydrophobic force in driving the aggregation is suggested. For the first time, DCI in aqueous solution is found to form a new aggregate which has both J- and H- bands.

• Journal of Microbiology and Biotechnology
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• v.19 no.12
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• pp.1628-1634
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• 2009

Small heat shock proteins (sHSPs) function as molecular chaperones that protect cells against environmental stresses. In the present study, the genes of hsp17.6 and hsp17.7, cytosolic class I sHSPs, were cloned from a tropical plant, Ageratina adenophorum. Their C-terminal domains were highly conserved with those of sHSPs from other plants, indicating the importance of the C-terminal domains for the structure and activity of sHSPs. The recombinant HSP17.6 and HSP17.7 were applied to determine their chaperone function. In vitro, HSP17.6 and HSP17.7 actively participated in the refolding of the model substrate citrate synthase (CS) and effectively prevented the thermal aggregation of CS at $45^{\circ}C$ and the irreversible inactivation of CS at $38^{\circ}C$ at stoichiometric levels. The prior presence of HSP17.7 was assumed to suppress the thermal aggregation of the model substrate CS. Therefore, this report confirms the chaperone activity of HSP17.6 and HSP17.7 and their potential as a protectant for active proteins.