• Biomolecules & Therapeutics
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• v.23 no.6
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• pp.525-530
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• 2015

Ceramide is the most abundant lipid in the epidermis and plays a critical role in maintaining epidermal barrier function. Overall ceramide content in keratinocyte increases in parallel with differentiation, which is initiated by supplementation of calcium and/or vitamin C. However, the role of metabolic enzymes responsible for ceramide generation in response to vitamin C is still unclear. Here, we investigated whether vitamin C alters epidermal ceramide content by regulating the expression and/or activity of its metabolic enzymes. When human keratinocytes were grown in 1.2 mM calcium with vitamin C ($50{\mu}g/ml$) for 11 days, bulk ceramide content significantly increased in conjunction with terminal differentiation of keratinocytes as compared to vehicle controls (1.2 mM calcium alone). Synthesis of the ceramide fractions was enhanced by increased de novo ceramide synthesis pathway via serine palmitoyltransferase and ceramide synthase activations. Moreover, sphingosine-1-phosphate (S1P) hydrolysis pathway by action of S1P phosphatase was also stimulated by vitamin C supplementation, contributing, in part, to enhanced ceramide production. However, activity of sphingomyelinase, a hydrolase enzyme that converts sphingomyelin to ceramide, remained unaltered. Taken together, we demonstrate that vitamin C stimulates ceramide production in keratinocytes by modulating ceramide metabolicrelated enzymes, and as a result, could improve overall epidermal barrier function.

• Toxicological Research
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• v.17
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• pp.109-115
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• 2001

Abrus agglutinin was purified from the kernels of Abrus precatorius by Sepharose 4B affinity column chromatography followed by Sephadex G-100 gel filtration column chromatography. About 1.25 g of abrus agglutinin was obtained from 1 kg of the kernels. The LD$_{50}$ of abrus agglutinin is 5 mg/kg of body weight, which is less toxic than that of abrin, 20$\mu\textrm{g}$/kg body weight. The amino acid sequence of abrus agglutinin was determined by protein sequencing techniques and deduced from the nucleotide sequence of a cDNA clone encoding full length of abrus agglutinin. There are 258 residues, 2 residues and 267 residues in the A-chain, the linker peptide and the B-chain of abrus agglutinin, respectively. Abrus agglutinin had high homology to abrin-a (77.8%). The 13 amino acid residues involved in catalytic function, which are highly conserved among abrin and ricin, were also conserved within abrus agglutinin. The protein synthesis inhibitory activity of abrus agglutinin ($IC_{50}$/ = 3.5 nM) was weaker than that of abrin-a (0.05 nM). By molecular modeling followed by site-directed mutagenesis showed that Pro199 of abrus agglutinin A-chain located in amphipathic helix H and corresponding to Asn200 of abrin A-chain, can induce bending of helix H. This bending would presumably affect the binding of abrus agglutinin A-chain to its target sequence GpApGpAp, in the tetraloop structure of 285 r-RNA subunit and this could be one of major factors contributing to the relatively weak protein synthesis inhibitory activity and toxicity of abrus agglutinin.n.

• Journal of Powder Materials
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• v.11 no.6 s.47
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• pp.477-485
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• 2004

Monodispersed flaky silver powder was obtained by controlling the ratios of $H_{2}O_{2}/NH_{3}$ and Agin in a mixed solution of ethylene glycol and ammonia with an addition of PVP. The effects of $NH_{3}/Ag,\; H_{2}O_{2}/Ag\;and\;H_{2}PtCl_{6}/Ag$ on its morphology and size were investigated. In $H_{2}O_{2}-NH_{3}-AgNO_{3}\;system,\;NH_{3}/Ag$ molar ratio was found to be an important reaction factor for the nucleation and crystal growth of Ag powder. The synthesis of flaky powder was optimized at over 6 of $NH_{3}/Ag \;and\;5\;of\;H_{2}O_{2}/Ag\;under\;1.0{\times}10^{-3}\;of\;Pt/Ag.\;Moreover,\;as\;the\; NH_{3}/Ag$ molar ratio increased, the size of precipitates was increased regardless of the amount of Pt. In the absence of $H_{2}PtCI$, the morphology and size of reduced Ag powder were found to be irregular in shape $2-4{\mu}m$ in diameter. However, homogenized fine Ag powder was obtained due to heterogeneous nucleation when $H_{2}PtCI$ used as a cat-alyst, and flaky one was synthesized with the addition of Pt over $1.0{\times}10^{-3}$ of Pt/Ag.

• Korean Chemical Engineering Research
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• v.53 no.6
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• pp.798-801
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• 2015

Nanomaterials (NMs) based on cadmium telluride (CdTe) are the theme of numerous research areas due to their unique chemical and physical properties. NM synthesis via a size-controlled procedure has become an intriguing research topic because NMs exhibit novel optical and physical properties depending on their size and shape. In this study, we prepared CdTe nanowires (NWs) via self-assembly from individual Nanoparticles (NPs). Thioglycolic acid (TGA)-to-Cd ion ratio of 1.3 was used instead of the traditional value of 2.4 and the reduced amount of stabilizer resulted in reorganization from individual NPs into NWs consisting of multi-layers of individual NPs. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were performed to characterize NWs. The produced nanowires were straight and long in shape and their length ranged from 500 nm to tens of micrometers.

• Bulletin of the Korean Chemical Society
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• v.34 no.12
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• pp.3835-3839
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• 2013

A new synthesis route for Pt nanoparticles by direct electrochemical reduction of a solid-state Pt ion precursor ($K_2PtCl_6$) is demonstrated. Solid $K_2PtCl_6$-supported polyethyleneimine (PEI) coatings on the surface of glassy carbon electrode were prepared by simple mixing of solid $K_2PtCl_6$ into a 1.0% PEI solution. The potential cycling or a constant potential in a PBS (pH 7.4) medium were applied to reduce the solid $K_2PtCl_6$ precursor. The reduction of Pt(IV) began at around -0.2 V and the reduction potential was ca. -0.4 V. A steady state current was achieved after 10 potential cycling scans, indicating that continuous formation of Pt nanoparticles by electrochemical reduction occurred for up to 10 cycles. After applying the reduction potential of -0.6 V for 300 s, Pt nanoparticles with diameters ranging from $0.02-0.5{\mu}m$ were observed, with an even distribution over the entire glassy carbon electrode surface. Characteristics of the Pt nanoparticles, including their performance in electrochemical reduction of $H_2O_2$ are examined. A distinct reduction peak observed at about -0.20 V was due to the electrocatalytic reduction of $H_2O_2$ by Pt nanoparticles. From the calibration plot, the linear range for $H_2O_2$ detection was 0.1-2.0 mM and the detection limit for $H_2O_2$ was found to be 0.05 mM.

• Journal of the Korean Ceramic Society
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• v.31 no.11
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• pp.1401-1413
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• 1994

The synthesis of kaolinite mineral from domestic diatomite for silica resource, commercial vailable gibbsite or alumina for alumina resource were made under various hydrothermal treatment, and the sythetic effect of acidic mineralizers, temperature treatment with time duration, particle size of alumina on formation of kaolinite mineral and the plastic properties of synthesized kaolinite were investigated. The various acidic mineralizers which are HCl, HNO3, H2SO4 and Oxalic acid were employed for hydrothermal reaction in the range of 0.01 mol/ι to 2 mol/ι concentration of each mineralizers. It was found that HCl in the level of 1 mol/ι solution produced highly yields of well-crystallized and platy form kaolinite mineral and gave the most effective extraction of iron oxide, compared to that of others, that HNO3 produced highly yield of kaolinite but lower extraction of iron oxide, that H2SO4 produced low yield of kaolinite and formed alunite mineral, and that oxialic acid formed spherical crystalline kaolinite and gave low extraction of iron oxide. Moreover, it showed that kaolinite minerals were well synthesized in a wide range of less than 2 mol/ι acids, but were poorly synthesized at more than 2 mol/ι acids. However, boehmite and kaolinite were coexistently formed in the temperature range of 18$0^{\circ}C$ and 20$0^{\circ}C$ when the calcined diatomite and gibbsite were involved. The well-ordered kaolinite mineral as a platy form was highly synthesized in the temperature range of 220 and 24$0^{\circ}C$, when the same marterials as above were used with treatment of 1 mol/ι HCl solution. The results also revealed that the size of crystalline platy form kaolinite, synthesized from alumina and calcined diatomite with treatment in 1 mol/ιHCl solution at 24$0^{\circ}C$, was much larger than that of gibbsite and calcined diatomite shown previously, and that kaolinite and corundum minerals were coexistently formed under any hydrothermal treatment conditions. The plasticity of synthesized kaolinite from under 2 ${\mu}{\textrm}{m}$ alumina and calcined diatomite was very poor, and that of the synthesized kaolinite from raw diatomite and gibbsite gave higher than that of calcined diatomite and gibbsite.

• Molecular & Cellular Toxicology
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• v.2 no.2
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• pp.81-88
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• 2006

Sphingolipid metabolites regulate many aspects of cell proliferation, differentiation, and apoptosis. In the present study, we have assessed the effects of the novel phytosphingosine derivative, N-acetylphytospingosine (NAPS), on the depigmentation of murine B16F10 melanoma cells, and have also attempted to identify the possible signaling pathway involved, in comparison with $C_{2}-ceramide$. NAPS and $C_{2}-ceramide$ both inhibited the growth of the B16F10 cells in a dose-dependent manner. Melanin content and tyrosinase activity were significantly reduced in response to treatment with NAPS and $C_{2}-ceramide$ at concentrations in a range between $1-5\;{\mu}M$. However, the levels of tyrosinase mRNA, as well as the levels of tyrosinase related protein-1 (TRP-1) and tyrosinase related protein-2 (TRP-2) genes and the level of tyrosinase protein remained unaffected by treatment with either NAPS or $C_{2}-ceramide$. We also attempted to determine the signaling pathway exploited by NAPS and $C_{2}-ceramide$. Interestingly, the phosphorylation of Akt/PKB at serine 473 by NAPS was reduced at the 5 minute mark, whereas $C_{2}-ceramide$ induced the phosphorylation of Akt/PKB at serine 473. Finally, Akt/PKB activity in the NAPS-treated cells was elevated in comparison with the untreated cells. LY294002, a specific PI3-K inhibitor which is located upstream of Akt/PKB, inhibited the phosphorylation of Akt/PKB, but induced an increase in melanin synthesis. These results suggest that the activation of Akt/PKB at serine 473 is related with the suppression of melanin production in the B16F10 mouse melanoma cells. Therefore, the mechanisms exploited by NAPS and $C_{2}-ceramide$ responsible for the depigmentation of B16F10 cells were concluded to involve the inhibition of melanosomal tyrosinase activity.

• Bulletin of the Korean Chemical Society
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• v.32 no.7
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• pp.2410-2412
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• 2011

Using a single step chemical synthesis, we synthesized the potential tumor imaging agent $^{99m}Tc$-diglucose-diethylenetriamine (DGTA) from diethylenetriamine and natural D-glucose. 10 min Incubation of 10 mg of precursor with 50 ${\mu}g$ of $SnCl_2{\cdot}2H_2O$ at room temperature yielded over 95% of $^{99m}Tc$ labeling. The stability for 6 hours in saline or human plasma was over 90%. In vitro tumor cell uptake assays using the SNU-C5 and 9 L cell lines showed that, in 0-400 mg/dL glucose medium, cell uptake of $^{99m}Tc$-DGTA was 1.5-8 times higher than that of [$^{18}F$]FDG. Moreover, [$^{18}F$]FDG uptake was dependent on glucose concentration in the medium, whereas cellular uptake of $^{99m}Tc$-DGTA was not dependent on glucose concentration, suggesting that the two compounds have different uptake mechanisms by tumor cells.

• Bulletin of the Korean Chemical Society
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• v.32 no.7
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• pp.2249-2252
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• 2011

Two new carborane complexes containing closo- or nido-carborane diphosphine ligands with the formula: complex $[Hg(7,8-(PPh_2)_2-7,8-C_2B_9H_{10})_2]$ $CH_2Cl_2$ (1) and $[Ag_2({\mu}-Cl)_2(1,2-(P^iPr_2)_2-1,2-C_2B_{10}H_{10})_2]$ (2) have been synthesized and characterized by elemental analysis, 1H and 13C NMR spectroscopy and X-ray structure determination. The X-ray structure analyses revealed that the carborane diphosphine ligand was degraded from closo-1,2-$(PPh_2)_2-1,2-C_2B_{10}H_{10}$ to nido-[$7,8-(PPh_2)_2-7,8-C_2B_9H_{10}]^-$ in complex 1, while the closo nature of the starting ligand $1,2-(P^iPr_2)_2-1,2-C_2B_{10}H_{10}$ was retained in complex 2. In either of the two complexes, the carborane diphosphine ligand was coordinated bidentately to the Hg(II) or Ag(I) center through its two phosphorus atoms, therefore forming a five-member cheating ring between the carborane ligand and the metal center. The coordination geometry of the metal atom is distorted tetrahedron formed by $P_4$ unit in complex 1 and $P_2Cl_2$ unit in complex 2, respectively.

• The Journal of Korean Medicine Ophthalmology and Otolaryngology and Dermatology
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• v.26 no.1
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• pp.1-18
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• 2013

Objective: Recently the demands for the effective and safe depigmentative and anti-aging agents of the skin have increased due to the medical, pharmaceutical and cosmetic reasons. The purpose of this study is to investigate the MKG(Methanol Extract of Kaempferia galanga) and their dermal bioactivity properties related to cosmeceuticals such as depigmentation. Methods: We assessed inhibitory effects of MKG on melanin production in B16/F10 melanoma cells, on mushroom tyrosinase activity, effects of MKG on the expression tyrosinase, TRP-1, TRP-2, GSK-$3{\beta}$, CREB, MITF in B16/F10 melanoma cells without cytotoxicity range. Cell viability was measured by MTT assay and tyrosinase activity was assessed using by DOPA staining, western-blot analysis. We measured inhibition of melanin synthesis and tyrosinase activity by down-regulation of melanogenic enzyme expressions in ${\alpha}$-MSH induced melanogenesis B16/F10 melanoma cells. Results: MKG inhibited tyrosinase-activity, total melanin contents and dendrite out-growth. MKG inhibited melanogenesis by down-regulation of tyorsinase, TRP-1, TRP-2, CREB, and MITF in B16/F10 cells. The treatment with MKG at the 12.5, $25{\mu}g/ml$ level significantly inhibited the melanin synthesis induced ${\alpha}$-MSH in B16/F10 melanoma cells compared with untreated control. Conclusion: These results suggest that MKG inhibit melanin biosynthesis which is involved in hyper-pigmentation. So MKG is considered to be used as a whitening components reducing cytotoxicity.