Kyungmoon Lee

Ajou University, Sŏul, Seoul, South Korea

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Publications (4)15.2 Total impact

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    ABSTRACT: Graphene, functionalized with oleylamine (OA) and soluble in non-polar organic solvents, was produced on a large scale with a high yield by combining the Hummers process for graphite oxidation, an amine-coupling process to make OA-functionalized graphite oxide (OA-GO), and a novel reduction process using trioctylphosphine (TOP). TOP acts as both a reducing agent and an aggregation-prevention surfactant in the reduction of OA-GO in 1,2-dichlorobenzene (DCB). The reduction of OA-GO is confirmed by X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, and Raman spectroscopy. The exfoliation of GO, OA-GO, and OA-functionalized graphene (OA-G) is verified by atomic force microscopy. The conductivity of TOP-reduced OA-G, which is deduced from the current–voltage characteristics of a vacuum-filtered thin film, shows that the reduction of functionalized GO by TOP is as effective as the reduction of GO by hydrazine.
    Carbon 07/2010; 48(8):2282-2289. DOI:10.1016/j.carbon.2010.03.002 · 6.16 Impact Factor
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    ABSTRACT: In this study, we investigated the process of X-ray-induced apoptosis of skin keratinocyte, and the functional role of protein kinase C delta (PKCdelta) and downstream signalling cascade. High-dose X-ray irradiation (10 Gy) led to the apoptosis of HaCaT keratinocyte, accompanied by PKCdelta cleavage. Treatment with PKCdelta inhibitor and adenoviral transduction of dominant-negative PKCdelta clearly inhibited the X-ray-induced apoptosis of keratinocyte. In addition, X-ray induced the phosphorylation of extracellular signal-regulated kinases 1/2 (ERK1/2) and inhibition by ERK1/2 inhibitor abrogated the X-ray-induced apoptosis. Interestingly, overexpression of dominant-negative PKCdelta markedly blocked the X-ray-induced phosphorylation of ERK1/2, suggesting that ERK1/2 is the functional downstream effector of PKCdelta. Next, we investigated the difference between UVB and X-ray response. UVB induced the apoptosis of keratinocyte in a PKCdelta-dependent manner, similar to X-ray response. However, UVB irradiation induced the phosphorylation of c-jun N-terminal kinases (JNK) and inhibition of JNK significantly protected the UVB-induced apoptosis. These results demonstrate that PKCdelta is a key regulator in X-ray-induced apoptosis of keratinocyte and suggest that there is subtle difference in downstream signalling cascade between UVB and X-ray response of keratinocyte.
    Experimental Dermatology 01/2009; 18(1):50-6. DOI:10.1111/j.1600-0625.2008.00761.x · 4.12 Impact Factor
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    ABSTRACT: Bending and bundling was observed from vertically aligned arrays of ZnO nanowires with flat (0001) top surfaces, which were synthesized using a vapor-phase method without metal catalysts. Sufficient evidence was found to exclude electron-beam bombardment during scanning electron microscopy as a cause for bending and bundling. We attribute the bending and bundling to electrostatic interactions due to charged (0001) polar surfaces, and also discussed the threshold surface charge densities for the bending and bundling based on a simple cantilever-bending model. Some growth features were indicative of the operation of electrostatic interactions during the growth.
    Nanotechnology 05/2008; 19(18):185607. DOI:10.1088/0957-4484/19/18/185607 · 3.67 Impact Factor
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    ABSTRACT: In a previous search for the differentially expressed genes in keratinocyte differentiation, we identified neutrophil gelatinase-associated lipocalin (NGAL) as a calcium-induced gene. In this study, we further verified the expression of NGAL in cultured keratinocytes as well as in several skin diseases. Reverse transcription-polymerase chain reaction (RT-PCR), Western blot, and ELISA clearly showed that NGAL expression was markedly increased in calcium-induced keratinocyte differentiation in vitro. However, in our previous report, NGAL expression was not detected in normal skin tissue except for hair follicle by in situ hybridization and immunohistochemistry, indicating the difference of cell status between in vitro and in vitro conditions. Interestingly, NGAL expression was highly increased in psoriasis-like inflammatory disorders (lichen planus and pityriasis rubura pilaris) and skin cancers (keratoacanthoma and squamous cell carcinoma), implying that NGAL may be related with the epidermal hyperplasia. Collectively, these results reveal the potential importance of NGAL in the maintenance of skin homeostasis.
    Journal of Korean Medical Science 05/2008; 23(2):302-6. DOI:10.3346/jkms.2008.23.2.302 · 1.25 Impact Factor