• Bulletin of the Korean Chemical Society
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• 제28권12호
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• pp.2539-2542
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• 2007

• 한국염색가공학회지
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• 제23권2호
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• pp.76-82
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• 2011

Ultra High molecular weight polyethylene(UHMWPE) films were photooxidized by UV/ozone irradiation. Reflectance of the irradiated films decreased in the low wavelength regions of visible light, indicating destructive interference of visible light due to roughened surface. The UV treatment developed the nano-scale roughness on the UHMWPE films surface, which increased by two-fold from 82.6 to 156.6nm in terms of peak-valley roughness. The UV irradiation caused the oxygen content of the UHMWPE film surface to increase. Water contact angle decreased from $83.2^{\circ}$ to $72.9^{\circ}$ and surface energy increased from 37.8 to 42.6mJ/$m^2$ with increasing UV energy. The surface energy change was attributed to significant contribution of polar component rather than nonpolar component indicating surface photooxidation of UHMWPE films. The increased dyeability to cationic dyes may be due to the photochemically introduced anionic and dipolar dyeing sites on the film surfaces.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2007년도 정기 학술대회 논문집
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• pp.427-432
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• 2007

In general, the response of bulk material is independent of its size when it comes to considering classical elasticity theory. Because the surface to bulk ratio of the large solids is very small, the influence of surface can be negligible. But the surface effect plays important role as the surface to bulk ratio becomes larger, that is, the contribution of the surface effect must be considered in nano-size elements such as thin film or beam structure. Molecular dynamics computation has been a conventional way to analyze these ultra-thin structures but this method is limited to simulate on the order of $10^6-10^8$ atoms for a few nanoseconds, and besides, very time consuming. Analysis of structures in submicro to micro range(thin-film, wire etc.) is difficult with classical molecular dynamics due to the restriction of computing resources and time. Therefore, in this paper, the continuum-based method is considered to simulate the overall physical and mechanical properties of the structures in nano-scale, especially, for the thin-film.

• 한국동물학회지
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• 제26권4호
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• pp.235-251
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• 1983

배양한 계배 근원세포의 융합기작을 밝혀보기 위해서 분화과정에 있는 근세포를 lactoperoxidase를 촉매로 써서 막표면단백질을 iodination하여 본 결과, 융합의 과정에서 막표면단백질의 정성적 및 정량적 변화를 볼 수 있었다. 융합전의 세포에서 12개의 주요단백질을 검출할 수 있었는데, 융합시의 세포에서는 165K와 93K의 단백질이 새롭게 나타났으며 동시에 245K 단백질의 감소와 저분자 단백질의 증가를 볼 수 있었다. 이 고분자 단백질의 감소는 세포주기와 관계가 있는 것으로 생각되고 있는 세포내 cAMP 수준은 융합에 앞서서 현저한 일시적인 증가를 보였는데, 이와같은 결과는 cAMP의 증가가 세포의 융합의 유발과 관계가 있음을 보여 주는 것이었으며, 분화하는 근원세포에서는 고도의 동조성이 보였다. 아울러, 근세포의 융합과정에서 적어도 4 가지의 iodination된 저분자 단백질을 배양액에서 발견할 수 있었는데, 이들은 막단백질의 가수분해산물로 생각되었고, 역시 세포의 융합과정과 유관할 것으로 추정되었다. 세포막 표면단백질의 변화, 분화과정 중에 배양액 속으로 방출되는 단백질, 융합과 유관한 cAMP의 증가 및 융합과 관련되는 외적 요인의 가능성에 관해서 논의하였다.

• 한국결정학회:학술대회논문집
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• 한국결정학회 2002년도 정기총회 및 추계학술연구발표회
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• pp.24-24
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• 2002

HtrA (high temperature requirement A), a periplasmic heat shock protein, is known to have molecular chaperone function at low temperatures and proteolytic activity at elevated temperatures. To investigate the mechanism of functional switch to pretense, we have determined the crystal structure of the N-terminal protease domain (PD) of HtrA from Thermotoga maritima. HtrA PD shares the same fold with chymotrypsin-like serine professes. However, crystal structure suggests that HtrA PD is not an active pretense at current state since its active site is not formed properly and blocked by an additional helical lid. On the surface of the lid, HtrA PD has hydrophobic patches that could be potential substrate binding sites for molecular chaperone activity. Present structure suggests that the activation of the proteolytic function of HtrA PD at elevated temperatures might occur by the conformational change.

• Animal cells and systems
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• 제1권4호
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• pp.657-663
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• 1997

The CD4 and CDS coreceptors, in conjunction with the T cell receptor (TCR) , make important contributions to the differentiation of thymocytes. They have been shown to be involved in the clonal deletion and positive selection processes during T cell development in thymus. To further analyze the role of CD4 and CDS proteins during T cell differentiation, we have generated transgenic mice constitutively expressing high levels of a native CD4 and a CD4{CDSa hybrid protein. The hybrid protein is composed of CD4 extracellular domain linked to the CD8a transmembrane region and cytoplasmic tail. The transgenes were driven by human beta-actin promoter, and therefore, they were expressed in all tissues examined including thymus, spleen, and lymph nodes. The resulting CD4 and CD4{CD8${\alpha}$transgenic mice were found to express the CD4 and CD4{CD8${\alpha}$ respectively, in developing thymocytes and peripheral T cells. The expression levels of transgenic proteins were 5-10 times higher than that of endogenous CD4 in thymus. However, total surface CD4 expression (CD4 or CD4{CD8${\alpha}$ transgenic protein plus endogenous CD4) of the transgenic mice were main. tained at similar levels compared to control littermates. Surface CD4 expression on CDS T cells, however, was significantly lower than that on cells expressing endogenous CD4. These results suggest that a total avidity between developing thymocytes and thymic stromal cells is impor. tant for differentiation of thymocytes.

• Macromolecular Research
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• 제17권7호
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• pp.458-463
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• 2009

Polyurethane (PU) is widely used as a cardiovascular biomaterial due to its good mechanical properties and hemocompatibility, but it is not adhesive to endothelial cells (ECs). Cell adhesive peptides, GRGDS and YIGSR, were found to promote adhesion and spreading of ECs and showed a synergistic effect when both of them were used. In this study, a surface modification was designed to fabricate an EC-active PU surface capable of promoting endothelialization using the peptides and poly(ethylene glycol) (PEG) spacer, The modified PU surfaces were characterized in vitro. The density of the grafted PEG on the PU surface was measured by acid-base back titration to the terminal-free isocyanate groups. The successful immobilization of pep tides was confirmed by amino acid analysis, following hydrolysis, and contact angle measurement. The uniform distribution of peptides on the surface was observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). To evaluate the EC adhesive property, cell viability test using human umbilical vein EC (HUVEC) was investigated in vitro and enhanced endothelialization was characterized by the introduction of cell adhesive peptides, GRGDS and YIGSR, and PEG spacer. Therefore, GRGDS and YIGSR co-immobilized PU surfaces can be applied to an EC-specific vascular graft with long-term patency by endothelialization.

• Bulletin of the Korean Chemical Society
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• 제30권8호
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• pp.1755-1759
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• 2009

Surface structure and molecular orientation of self-assembled monolayers (SAMs) formed by the spontaneous adsorption of tetrahydrothiophene (THT) and thiophene (TP) on Au(111) were investigated by means of scanning tunneling microscopy (STM) and carbon K-edge near edge X-ray absorption fine structure (NEXAFS) spectroscopy. STM imaging revealed that THT SAMs have a commensurate (3 ${\times}\;2\sqrt[]{3}$) structure containing structural defects in ordered domains, whereas TP SAMs are composed of randomly adsorbed domains and paired molecular row domains that can be described as an incommensurate packing structure. The NEXAFS spectroscopy study showed that the average tilt angle of the aliphatic THT ring and $\pi$-conjugated TP ring in the SAMs were calculated to be about $30^o\;and\;40^o$, respectively, from the surface normal. It was also observed that the $\pi$* transition peak in the NEXAFS spectrum of the TP SAMs is very weak, suggesting that a strong interaction between $\pi$-electrons and the Au surface arises during the self-assembly of TP molecules. In this study, we have clearly demonstrated that the surface structure and adsorption orientation of organic SAMs on Au(111) are strongly influenced by whether the cyclic ring is saturated or unsaturated.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2009년도 춘계학술대회 논문집
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• pp.91-91
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• 2009

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2009년도 춘계학술대회 논문집
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• pp.92-92
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• 2009