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JH Lee

Publications and source records attributed to JH Lee.

At least 19 recordsLinked to original sources
PubMed2000

Remarkable Anionic Axial Ligand Effects of Iron(III) Porphyrin Complexes on the Catalytic Oxygenations of Hydrocarbons by H(2)O(2) and the Formation of Oxoiron(IV) Porphyrin Intermediates by m-Chloroperoxybenzoic Acid This work was supported by Center for Cell Signaling Research (1999-2-122-002-4), the Korean Research Foundation (KRF-99-042-D00068), and the MOST through the Women's University Research Fund (99-N6-01-01-A-07).

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PubMed2000

The Effect of Fluid Shear Stress on Endothelial Cell Adhesiveness to Polymer Surfaces with Wettability Gradient.

In this study, the adhesive strength of endothelial cells (ECs) attached on polymer surfaces with different hydrophilicity was investigated using wettability gradient polyethylene (PE) surfaces prepared by corona discharge treatment from a knife-type electrode whose power increases gradually along the sample length. The EC-attached wettability gradient surfaces were mounted on parallel-plate flow chambers in a flow system prepared for cell adhesiveness test. Three different shear stresses (150, 200, and 250 dyne/cm(2)) were applied to the flow chambers and each shear stress was maintained for 120 min to investigate the effect of shear stress and surface hydrophilicity on the EC adhesion strength. It was observed that the ECs were adhered more onto the positions with moderate hydrophilicity of the wettability gradient surface than onto the more hydrophobic or hydrophilic positions. The maximum adhesion of the cells appeared at around water contact angles of 55 degrees. The EC adhesion strength was higher on the hydrophilic positions than on the hydrophobic ones. However, the maximum adhesion strength of the cells also appeared at around water contact angles of 55 degrees. More than 90% of the adhered cells remained on that position after applying the shear stress, 250 dyne/cm(2) for 2 h, whereas the cells were completely detached on the hydrophobic position (water contact angle, about 86 degrees ) within 10 min after applying the same shear stress. It seems that surface hydrophilicity plays a very important role for cell adhesion strength. Copyright 2000 Academic Press.

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PubMed2000

Growth with surface curvature on quenched potentials

A discrete growth model driven by the Laplacian of the surface curvature in quenched random media is discussed. The interface width W at the saturated regime obeys scaling W approximately Lalpha with alpha approximately 2.3, where L is the system size. Starting from an initial sine wave condition of a selected wavelength, we measure an autocorrelation function, and obtain the dynamic critical exponent z approximately 3.1. The model is expected to be described by the quenched Mullins-Herring equations.

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PubMed1999

The crystal structure of the B-site ordered complex perovskite Sr(Yb0.5Nb0.5)O3.

The room-temperature crystal structure of the B-site ordered complex perovskite strontium ytterbium niobate, Sr(Yb(0.5)Nb(0.5))O(3) [monoclinic, Z = 2, P2(1)/n (set 2), a = 5.79095 (8), b = 5.82210 (7), c = 8.20358 (12) Å, beta = 90.126 (1) degrees, with final R(wp) = 0.0595, R(Bragg) = 0.0203 for the neutron profile and R(wp) = 0.0832, R(Bragg) = 0.0193 for the X-ray profile, respectively], was determined by X-ray powder diffraction, high-resolution neutron powder diffraction and transmission electron microscopy. This compound shows a slight triclinic distortion from the prototype doubled cubic perovskite cell as a result of an a(-)a(-)c(+)-type oxygen octahedral tilting distortion. It is also shown that the site ordering of the different species of B-site cations, Yb(3+) and Nb(5+), inherently leads to a difference between the volumes of the YbO(6) and NbO(6) octahedra. This volume difference is shown to inevitably inhibit the rigid rotation of octahedra.

Journal Article↗
PubMed1999

Complementary DNA Encoding nm23/NDP Kinase Gene from the Korean Tiger Shark Scyliorhinus torazame.

: A new tumor suppressor gene, snm23, homologous to the gene for human nucleoside diphosphate kinase nm23/NDP was first cloned from Korean tiger shark (Scyliorhinus torazame) skin lambda ZAP-II complementary DNA library. The gene (named snm23) containing the tumor metastasis suppressor protein was sequenced. The nucleotide and deduced amino acid sequences of snm23 revealed an open reading frame of 450 bp that corresponded to a protein of 150 amino acid residues, with a calculated molecular mass of 16.8 kDa. Sequence comparison of snm23 with nm23/NDP kinases was performed. In order to determine tissue specificity, reverse transcription-polymerase chain reaction was used. The expression of snm23/NDP kinase was detected in tissues from skin, cartilage, and liver of Korean tiger shark.

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PubMed1999

Optimal pH control of batch processes for production of curdlan by Agrobacterium species.

We sought an optimal pH profile to maximize curdlan production in a batch fermentation of Agrobacterium species. The optimal pH profile was calculated using a gradient iteration algorithm based on the minimum principle of Pontryagin. The model equations describing cell growth and curdlan production were developed as functions of pH, sucrose concentration, and ammonium concentration, since the specific rates of cell growth and curdlan production were highly influenced by those parameters. The pH profile provided the strategy to shift the culture pH from the optimal growth condition (pH 7.0) to the optimal production one (pH 5.5) at the time of ammonium exhaustion. By applying the optimal pH profile in the batch process, we obtained significant improvement in curdlan production (64 g L-1) compared to that of constant pH operation (36 g L-1).

Journal Article↗
PubMed1998

Interaction of Different Types of Cells on Polymer Surfaces with Wettability Gradient.

Gradient surfaces whose properties are changed gradually along the sample length are of particular interest for basic studies of the interaction between biological species and surfaces since the effect of a selected property can be examined in a single experiment on one surface. We prepared a wettability gradient on low density polyethylene (PE) sheets by treating them in air with the corona from a knife-type electrode whose power increases gradually along the sample length. The PE surfaces oxidized gradually with the increasing corona power, and the wettability gradient was created on the surfaces as evidenced by the measurement of water contact angles, Fourier transform infrared spectroscopy in the attenuated total reflectance mode, and electron spectroscopy for chemical analysis. The wettability gradient surfaces prepared were used to investigate the interaction of different types of cells (Chinese hamster ovary, fibroblast, and endothelial cells) as well as serum proteins in terms of the surface hydrophilicity/hydrophobicity of polymeric materials. The cells adhered and grown on the gradient surface along the sample length were counted and observed by scanning electron microscopy. It was observed that the cells were adhered, spread, and grown more onto the positions with moderate hydrophilicity of the wettability gradient surface than onto the more hydrophobic or hydrophilic positions. The maximum adhesion and growth of the cells appeared at around water contact angles of 55 degrees, regardless of the cell types used. This result seems closely related to the serum protein adsorption on the surfaces; the serum proteins were also adsorbed more onto the positions with moderate hydrophilicity of the wettability gradient surface. Copyright 1998 Academic Press.

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