• Bulletin of the Korean Chemical Society
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• v.12 no.6
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• pp.686-691
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• 1991

Emission quenching of photoexcited tris(${\alpha},{\alpha} '$-diimine)-ruthenium(II) complex cations, $RuL_3^{2+}$ (L: 2,2'-bipyridine, 4,4'-dimethyl-2,2'-bipyridine; 4,4'-diphenyl-2,2'-bipyridine; 1,10-phenanthroline; 5-methyl-1,10-phenanthroline; 5,6-dimethyl-1,10-phenanthroline or 4,7-diphenyl-1,10-phenanthroline) by $Cu^{2+}$, dimethylviologen $(MV^{2+})$, nitrobenzene (NB), and oxygen was studied in aqueous homogeneous and sodium dodecyl sulfate (SDS) micellar solutions. The apparent bimolecular quenching rate constants $k_q$ were determined from the quenching data and life-times of $^{\ast}RuL_3^{2+}$. In homogeneous media, the quenching rate was considerably slower than that for the diffusion-controlled reaction. The decreasing order of quenching activity of quenchers was $NB>O_2>MV^{2+}>Cu^{2+}$. The rate with $Cu^{2+}$ was faster as the reducing power of $^{\ast}RuL_3^{2+}$ is greater. On the other hand, the rates with NB and $O_2$ were faster as the ligand is more hydrophobic. This was attributed to the stabilization of encounter pair by van der Waals force. The presence of SDS enhanced the rate of quenching reactions with $Cu^{2+}$ and $MV^{2+}$, whereas it attenuated the quenching activity of NB and $O_2$ toward $RuL_3^{2+}$. The binding affinity of quenchers to SDS micelle and binding sites of the quenchers and $RuL_3^{2+}$ in micelle appear to be important factors controlling the micellar effect on the quenching reactions.

• Natural Product Sciences
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• v.28 no.2
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• pp.45-52
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• 2022

The identification of Plasmodium falciparum enoyl acyl-carrier protein reductase (pfENR) is considered as a potential biological target against malaria. Trema orientalis is considered a rich source of phytochemicals useful in malaria treatment. This study evaluated the in-vitro inhibitory activity of the extract and isolated compounds of T. orientalis leaf; the isolated compounds and the analogues of the most active compound were subjected to in-silico molecular docking studies on pfENR. The methanolic extract of T. orientalis was subjected to repeated chromatographic separation which led to the isolation of some compounds. The isolated compounds from the plant were examined for their antimalarial activity using β-hematin inhibition assay. Virtual screening via molecular docking and ADMET studies were conducted to gain insight into the mechanism of binding of ligand and to identify effective pfENR inhibitors. The isolated compounds and the analogues of the most active isolates were gotten from PubChem library for use in docking study. Hexacosanol and β-sitosterol showed inhibition of the β-hematin formation. The docking results showed that hexacosanol, β-sitosterol and the analogues of β-sitosterol displayed binding energy ranging between -6.1 kcal/mol and -11.6 kcal/mol. Sitosterol glucoside has the highest docking score. Some of the ligands showed more binding affinity than known bioactive compounds used as reference. Analogues of β-sitosterol has been shown to be potential inhibitors of pfENR, therefore, the findings from this study suggest that sitosterol glucoside and ergosterol peroxide could act as antimalarial agents after further lead optimisation investigations.

• The Korean Journal of Pharmacology
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• v.32 no.3
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• pp.311-321
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• 1996

Both $M_1$ and $M_2$ muscarinic receptors contain a triplet of amino acid residues consisting of leucine (L), tyrosine (Y) and threonine (T) at C-terminus ends of the second putative transmembrane domains. This triplet is repeated as LYT-LYT in $M_2$ receptors at the interface between the second transmembrane domain and the first extracellular loop. Interestingly, however, it is repeated in a transposed fashion (LYT-TYL) in the sequence of $M_1$ receptors. In this work, we employed site-directed mutagenesis to investigate the possible significance of this unique sequence diversity for determining the distinct differential cellular function at the two receptor subtypes. Mutation of the LYTTYL sequence of $M_1$ receptors to the corresponding $M_2$ receptor LYTLYT sequence did not result in a significant change in the binding affinity of the agonist carbachol. The reverse mutation at the $M_2$ receptor also did not modify agonist affinity. Surprisingly, the LYTLYT $M_1$ receptor mutant demonstrated markedly enhanced coupling to activation of phospholipase C without a change in its coupling to increased cyclic AMP formation. There was also an enhanced receptor sensitivity in transducing elevation of intracellular $Ca^{2+}$. On the other hand, the reverse $LYTLYT{\rightarrow}LYTTYL$ mutation in the $M_2$ receptor did not alter its coupling to inhibition of adenylate cyclase, but slightly enhanced its coupling to stimulation of phosphoinositide (PI) hydrolysis. Our data suggest that the LYTTYL/LYTLYT sequence differences between $M_1$ and $M_2$ muscarinic receptors are not important for specifying ligand binding and coupling of various subtypes of muscarinic receptors to different cellular signaling pathways although they might play a role in the modulation of muscarinic reseptor coupling to PI hydrolysis.

• BMB Reports
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• v.40 no.5
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• pp.731-739
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• 2007

The purpose of this study was to develop paclitaxel-loaded poly(lactide-co-glycolide) (PLGA) nanoparticles coated with cationic SM5-1 single-chain antibody (scFv) containing a polylysine (SMFv-polylys). SM5-1 scFv (SMFv) is derived from SM5-1 monoclonal antibody, which binds to a 230 kDa membrane protein specifically expressed on melanoma, hepatocellular carcinoma and breast cancer cells. SMFv-polylys was expressed in Escherichia coli and purified by cation-exchange chromatography. Purified SMFv-polylys was fixed to paclitaxel-loaded PLGA nanoparticles to form paclitaxel-loaded PLGA nanoparticles coated with SMFv-polylys (Ptx-NP-S). Ptx-NP-S was shown to retain the specific antigen-binding affinity of SMFv-polylys to SM5-1 binding protein-positive Ch-hep-3 cells. Finally, the cytotoxicity of Ptx-NP-S was evaluated by a non-radioactive cell proliferation assay. It was demonstrated that Ptx-NP-S had significantly enhanced in vitro cytotoxicity against Ch-hep-3 cells as compared with non-targeted paclitaxel-loaded PLGA nanoparticles. In conclusion, our results suggest that cationic SMFv-polylys has been successfully generated and may be used as targeted ligand for preparing cancer-targeted nanoparticles.

• Journal of Life Science
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• v.22 no.7
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• pp.863-870
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• 2012

Rhodopsin, a dim light photoreceptor, has been regarded as one of the model systems for the structural and functional study of G protein-coupled receptors (GPCRs). Constitutively active mutant GPCRs leading to the activation of heterotrimeric GDP/GTP-binding protein signaling in the absence of ligand binding are of interest for the study of the activation mechanism in GPCRs. The present study focused on the opsin mutant E134Q/M257Y, which showed a moderate level of constitutive activity and the formation of two distinct rhodopsin chromophores with absorption maxima of 500 nm and 380 nm, depending on the presence of an inverse agonist, 11-cis-retinal, and an agonist, all-trans-retinal, respectively. Reconstitution of the mutant rhodopsin upon incubation with different ratios of 11-cis-retinal and the all-trans-retinal, as well as upon sequential binding of the two retinals, indicated its preferential binding to 11-cis-retinal. The thermal stability of the 11-cis-retinal-bound form of the E134Q/M257Y mutant was lower than that of the mutants containing a single replacement but higher than that of the all-trans-retinal-bound forms. The mutant also showed a lower stability in its opsin state as compared with that of the wild-type opsin but had little effects on the binding affinity to 11-cis-retinal. Information obtained in this study will be helpful for analyzing the structural changes associated with the activation of rhodopsin and GPCRs.

• Journal of Life Science
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• v.28 no.3
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• pp.284-292
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• 2018

The melanin-concentrating hormone (MCH), a cyclic hypothalamic peptide composed of 17 amino acids, was initially identified in chum salmon (Oncorhynchus keta) as a regulator of pigmentation. Mammalian MCHs are cyclic hypothalamic peptides composed of 19 amino acids that regulate food intake and energy homeostasis. The present study examined not only MCH expression of different tissues but also the melanohore aggregation and intracellular $Ca^{2+}$ influx of fMCH and the other MCH. Real-time qPCR showed that MCH expressed specially in the brain, gonad, and ovary, and expression of MCH was observed during the developmental stages. In the application of synthetic fMCH and both types of synthetic fMCH, dN-fMCH and dC-fMCH, scale melanophore induced significant changes in aggregation activity with various concentrations of MCH. Also, compared to hMCH and sMCH, fMCH exhibited a 36~99.85% increase in relative potency (%), whereas aggregation of dN-fMCH and dC-fMCH remained in a high concentration. However, dispersion was induced rapidly according to be low concentration of dN-fMCH and dC-fMCH. We show that fMCH and its derivates were bound human MCHR1 and rat MCHR expressed in HEK293T cells with nano-molar affinity and are likely to be ligand-induced to mobilize intracellular $Ca^{2+}$. These results may provide new ligands for binding assay with MCHew ligands, as a structure similar to the mammalian MCH structure was discovered in fish. Once the fMCH receptor system is in place, it can be compared to the MCH system of mammals in terms of MCH function.

• Biomedical Science Letters
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• v.12 no.2
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• pp.73-79
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• 2006

Nebulin is a giant ($600{\sim}900$ kDa), modular sarcomeric protein proposed to regulate the assembly, and to specify the precise lengths of actin filamints in vertebrate skeletal muscles. Recently, There is an evidence that the nebulin also expressed in non muscle tissue, brain and liver. We identified a new isoform of nebulin from adult brain library by PCR screening. It contains two simple-repeats exon 165, 166 and linker-repeats exon $154{\sim}161$ except exon 159. The nebulin modules M160 to M170 (exon 150 to exon 161) has been shown to bind desmin. In mature striated muscle, desmin intermediate filaments surround Z-discs and link individual myofibrils laterally at their Z-discs and to other intracellular structures, including the costameres and the intercalated discs of the sarcolemma, sarcoplasmic reticulum, mitochondria, T-tubules, and nuclei. Therefore, it is an interesting possibility that the differential splice pathways within the linker region of nebulin modify the affinity of nebulin's interaction with desmin. The specific interactions of nebulin and desmin were confirmed in vivo by yeast two hybrid experiments. To verify in the cellular level the interaction between nebulin isoform and desmin, we transfected COS-7 cell with EGFP-tagged nebulin and DsRed-tagged desmin. Based on evidence showing that despite exon 159 was deleted, the new isoform of nebulin was interact with desmin. This suggest that nebulin in brain may interact with another intermediate filament. The conservation of these ligand-binding capacity in brain and skeletal nebulins suggest that nebulins may have conserved roles in brain and skeletal muscle.

• Parasites, Hosts and Diseases
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• v.26 no.2
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• pp.87-94
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• 1988

By affinity chromatography using a monoclonal antibody as ligand, Kim et at. (1986) purified a protein fraction in cystic fluid of Taenia solium metacestodes (CF) In this study, the biochemical properties of the purified protein were characterized. Discontinuous-polyacrylamide gel electrophoresis (disc-PAGE) of the protein at 4.5∼10% separating gel concentration showed its molecular weight (MW) to be 150 kilodalton (kDa) in non·denatured state, while denaturing sodium dodecyl suifate-polyacrylamide gel electrophoresis (SDS-PAGE) revealed that it was composed of 3 different subunits with respective fnw of 15, 10 and 7 kDa. Subunit of 7 kDa was shown to be linked to other subunits by disulade bonds. Isoelectric point of the protein was pH 6.8. The protein was relatively heat-stable for immunologic analysis. These properties indicated that the protein, comprising about 70% of total content in CF, had similar biochemical characters with antigen B of Oriol et at.(1971) in hydatid cyst quid (HF).

• BMB Reports
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• v.53 no.9
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• pp.478-483
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• 2020

Kudoa septempunctata is a myxozoan parasite that causes food poisoning in individuals consuming olive flounder. The present study aimed to investigate the currently insufficiently elucidated early molecular mechanisms of inflammatory responses in the intestine owing to parasite ingestion. After Kudoa spores were isolated from olive flounder, HT29 cells were exposed to spores identified to be alive using SYTO-9 and propidium iodide staining or to antigens of Kudoa spores (KsAg). IL-1β, IL-8, TNF-α and NFKB1 expression and NF-κB activation were assessed using real-time PCR, cytokine array and western blotting. The immunofluorescence of FITC-conjugated lectins, results of ligand binding assays using Mincle-Fc and IgG-Fc, CLEC4E expressions in response to KsAg stimulation, and Mincle-dependent NF-κB activation were assessed to clarify the early immune-triggering mechanism. Inflammatory cytokines (IL-1β, GM-CSF and TNF-α), chemokines (IL-8, CCL2, CCL5 and CXCL1) and NF-κB activation (pNF-κB/NF-κB) in HT29 cells increased following stimulation by KsAg. The immunofluorescence results of spores and lectins (concanavalin A and wheat germ agglutinin) suggested the importance of Mincle in molecular recognition between Kudoa spores and intestinal cells. Practically, data for Mincle-Fc and KsAg binding affinity, CLEC4E mRNA expression, Mincle immunofluorescence staining and hMincle-dependent NF-κB activation demonstrated the involvement of Mincle in the early immune-triggering mechanism. The present study newly elucidated that the molecular recognition and immune-triggering mechanism of K. septempunctata are associated with Mincle on human intestinal epithelial cells.

• The Journal of the Korea Contents Association
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• v.15 no.9
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• pp.418-424
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• 2015

In this study, we proceed if there are any changes in binding ability of receptor-ligand in some degree of SA and in radioactive uptake from the corpus striatum based on small animal experiment in vivo based on the S.A values. By dividing 18F-Fallypride into 3 S.A values(high S.A : 43.29~74 GBq/umol, ordinary S.A : 20.72~29.23 GBq/umol, low S.A : 6.29~8.51 GBq/umol), we injected directly into the veins and performed 90 minutes of dynamic scan using Micro PET. After scanning, we compared and analyzed with Binding Potential (Binding Potential) from the bilateral striatum. high SA and low SA, ordinary SA and low SA showed significant differences. Also, in the image comparison using 18F-Fallypride show high radioactive uptake in the striatum at high SA and ordinary SA, but the radioactive uptake at low SA is lower than other two SA. Since 18F-Fallypride has affinity to dopamine D2/3 pharmacokinetic, the difference of Binding Potentials at decreased level of SA values was not that significant. However, further PET research of the corpus striatum using 18F-Fallypride is necessary because the differences in images and Binding Potentials at 6.5 times smaller SA values compared to high SA value showed were significant.