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Ho-Young Kim

Publications and source records attributed to Ho-Young Kim.

10 recordsLinked to original sources
PubMed2006

How the capillary burst microvalve works.

The capillary burst microvalve offers an attractive means to regulate microliquid flow owing to its simple structure and operation process. However, there existed no rigorous theoretical work to elucidate how the valve works and consequently to predict the valve-bursting condition. Therefore, here we report the theoretical investigation of how the capillary burst valve can stop the advancing liquid meniscus and when it bursts. We confirm our theory with experiments using a centrifugal microfluidic valve system fabricated by soft lithography.

Microfluidics↗
PubMed2006

Functional analysis of a calcium-binding transcription factor involved in plant salt stress signaling.

Calcium is known to serve as a secondary messenger to mediate salt stress signaling pathway. We found a calcium-binding basic/helix-loop-helix-type transcription factor (AtNIG1) as a salt stress-responsive gene by using the suppression subtractive hybridization. The AtNIG1 was targeted into nucleus and bound to (45)Ca(2+), suggesting that AtNIG1 is a nuclear calcium-binding protein. In addition, AtNIG1 bound specifically to the E-box-DNA sequence (CANNTG), which is found in the promoter regions of many salt stress-related genes. Functional analyses with an atnig1-1 knockout mutant revealed that the mutant plants show enhanced sensitivity to salt stress. Further analyses indicated that the atnig1-1 plants have reduced survival rate, fresh weight, chlorophyll content, and protein content upon salt stress, suggesting that the AtNIG1 plays a critical role in plant salt stress signaling. Therefore, this study represents that AtNIG1 is the first known calcium-binding transcription factor involved in plant salt stress signaling.

Active Transport, Cell Nucleus↗
PubMed2006

The load supported by small floating objects.

We consider the equilibrium flotation of a two-dimensional cylinder and a sphere at an interface between two fluids. We give conditions on the density and radius of these objects for them to be able to float at the interface and discuss the role played by the contact angle in determining these conditions. For cylinders with a small radius, we find that the maximum density is independent of contact angle but that, for spheres, the contact angle enters at leading order in the particle radius. Our theoretical predictions are in agreement with experimental results.

Journal Article↗
PubMed2006

Dynamics of surfactant-driven fracture of particle rafts.

We investigate the dynamic fracture of a close-packed monolayer of particles, or particle raft, floating at a liquid-gas interface induced by the localized addition of surfactant. Unusually for a two-dimensional solid, our experiments show that the speed of crack propagation here is not affected by the elastic properties of the raft. Instead it is controlled by the rate at which surfactant is advected to the crack tip by means of the induced Marangoni flows. Further, the velocity of propagation is not constant in time and the length of the crack scales as t(3/4). More broadly, this surfactant-induced rupture of interfacial rafts suggests ways to manipulate them for applications.

Air↗
PubMed2006

Molecular characterization of a bHLH transcription factor involved in Arabidopsis abscisic acid-mediated response.

The suppression subtractive hybridization (SSH) method was used to isolate abscisic acid (ABA)-regulated genes in Arabidopsis. We report that the AtAIG1 gene is up-regulated by ABA and the AtAIG1 encodes a basic/helix-loop-helix (bHLH)-type transcription factor in Arabidopsis. The AtAIG1 was targeted into nucleus and bound to the E-box-DNA sequence, which is found in the promoter regions of many ABA-responsive genes. Functional analyses with the ataig1 knockout mutants revealed that the mutant plants show enhanced sensitivity to ABA. In addition, the ataig1 plants showed reduced expression of ABA-responsive genes, such as RD29A and RD22. Thus, these functional analyses suggest that the AtAIG1 protein plays an important role in ABA-mediated signal transduction pathway.

Abscisic Acid↗
PubMed2006

Sinking of a horizontal cylinder.

We study the sinking of a dense cylinder initially supported horizontally at an air-water interface and then released. The sinking motion is studied experimentally and agrees quantitatively with a simple hydrodynamic model of the process. In particular, our model predicts that the time taken for the cylinder to become immersed in the liquid should be tsink approximately theta((lc/g)1/2), where lc is the capillary length and g the acceleration due to gravity, in good agreement with what is observed experimentally.

Journal Article↗
PubMed2002

Sliding of liquid drops down an inclined solid surface.

A liquid drop that partially wets a solid surface will slide down the plane when it is tilted beyond a critical inclination. Here we report the study of the sliding velocity of such a drop. Experiments for measuring the steady sliding velocity of different liquids of drops are performed. We then construct a scaling law that predicts the sliding velocity given the physical properties, wetting characteristics, and size of the drop. When the sliding velocity is low and the drop distortion due to inclination is small, the scaling law is shown to correctly model the functional dependency of the measured sliding velocity.

Journal Article↗
PubMed2002

Aberrant splicing of FHIT transcripts in human gastric cancer cell lines.

Alterations of the FHIT gene occur as frequent events in several human cancers. Replacement of exogenous wild-type FHIT gene has been shown to induce suppression of tumorigenicity of human FHIT-negative cells in nude mice and aberrant FHIT transcripts have been observed in a variety of human solid tumors. In the presence study, we performed a nested reverse transcription-polymerase chain reaction (RT-PCR) analysis to identify aberrant FHIT transcripts in 6 gastric cancer cell lines. In addition to the wild-type FHIT transcript, small-sized transcripts with various number and lengths were observed in all of the cell lines examined. Sequence analysis confirmed that different types of truncated transcripts included exonic deletions, insertions of intron 5 sequences between exons, and combinations of both. Most of these transcripts lacked exon 5 in which translation initiation codon is located. Aberrant transcripts with partial exonic deletions, resulting from activation of cryptic splice sites, were also observed in 5 cell lines. Additionally, multi-step splice patterns, indicative of additional downstream processing, were observed in several cancer lines. Our results suggest that the aberrant FHIT transcripts in gastric cancer cell lines resulted from faulty splicing, including exon skipping, selection of cryptic splice site and additional downstream splice processing.

Acid Anhydride Hydrolases↗
PubMed2002

Expression of the fragile histidine triad gene in normal rat tissues and human kidney cancer cell lines.

The fragile histidine triad (FHIT) gene located in human chromosome 3p14.2 is a candidate tumor suppressor gene that has a diadenosine triphosphate (Ap3A) hydrolase activity, but its role in carcinogenesis remains uncertain. To investigate the role of FHIT in normal cells, specific polyclonal antibodies to recombinant rat FHIT protein were generated. Immunoblot analysis revealed the 17-kd FHIT protein was most abundantly expressed in kidney and liver, whereas heart, skeletal muscle, and adrenal gland expressed trace amounts. In kidney, immunohistochemical staining was strongly observed in distal convoluted tubule and collecting duct during postnatal growth period. By a nested reverse transcription-PCR analysis of FHIT from 2 human kidney cancer cell lines, four abnormal-sized FHIT transcripts, with deletion and/or insertion, were detected. These were derived from the results of exon skipping, and/or insertion of FHIT intron 5 sequence, or selection of cryptic splice site within the FHIT cDNA sequence 179-180. Taken together, our data indicate that FHIT expression is frequently altered in human kidney cancer cell lines by alternative splicing, and suggest that the FHIT protein may play a pivotal role in regulating intracellular metabolism of the distal convoluted tubule and collecting duct in maturity.

Acid Anhydride Hydrolases↗