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Biomedical subjects

Sung Ha Park

Publications and source records attributed to Sung Ha Park.

8 recordsLinked to original sources
PubMed2006

Age-related slip avoidance strategy while walking over a known slippery floor surface.

When confronted with impending slip/fall situations, gait parameters are adjusted accordingly to avoid slipping. This study was conducted to assess age-related slip avoidance strategy by measuring gait parameters and muscle activity characteristics of the lower extremities (hamstrings, calves, and quadriceps) of both young and older participants while ambulating successfully over a known slippery floor surface. Fourteen younger and 14 older adults participated in this study. First, a baseline measure was collected to study normal gait prior to any exposure to slipping. A second measure was collected following a slip from a contaminated floor surface, but before the initiation of a second slip, where the participants were able to view the contaminated surface before traversing it. The results indicated that there were significant gait parameter differences between normal-dry walking conditions and contaminated-slippery walking conditions. In general, participants (young and old) reduced step length, friction utilization, and heel contact velocity from normal gait to adjusted gait conditions. Furthermore, results also indicated that there were differences in gait parameters and muscle activity characteristics between the two age groups for both a normal gait condition and a gait condition requiring adjustment. Findings suggested that older individuals required an additional step to properly adjust gait for a contaminated walking surface.

Accidental Falls↗
PubMed2005

Three-helix bundle DNA tiles self-assemble into 2D lattice or 1D templates for silver nanowires.

We present a DNA nanostructure, the three-helix bundle (3HB), which consists of three double helical DNA domains connected by six immobile crossover junctions such that the helix axes are not coplanar. The 3HB motif presents a triangular cross-section with one helix lying in the groove formed by the other two. By differential programming of sticky-ends, 3HB tiles can be arrayed in two distinct lattice conformations: one-dimensional filaments and two-dimensional lattices. Filaments and lattices have been visualized by high-resolution, tapping mode atomic force microscopy (AFM) under buffer. Their dimensions are shown to be in excellent agreement with designed structures. We also demonstrate an electroless chemical deposition for fabricating metallic nanowires templated on self-assembled filaments. The metallized nanowires have diameters down to 20 nm and display Ohmic current-voltage characteristic.

DNA↗
PubMed2005

Programmable DNA self-assemblies for nanoscale organization of ligands and proteins.

We demonstrate the precise control of periodic spacing between individual protein molecules by programming the self-assembly of DNA tile templates. In particular, we report the application of two self-assembled periodic DNA structures, two-dimensional nanogrids, and one-dimensional nanotrack, as template for programmable self-assembly of streptavidin protein arrays with controlled density.

DNA↗
PubMed2004

DNA-templated self-assembly of protein and nanoparticle linear arrays.

Self-assembling DNA tiling lattices represent a versatile system for nanoscale construction. Self-assembled DNA arrays provide an excellent template for spatially positioning other molecules with increased relative precision and programmability. Here we report an experiment using a linear array of DNA triple crossover tiles to controllably template the self-assembly of single-layer or double-layer linear arrays of streptavidin molecules and streptavidin-conjugated nanogold particles through biotin-streptavidin interaction. The organization of streptavidin and its conjugated gold nanoparticles into periodic arrays was visualized by atomic force microscopy and scanning electron microscopy.

Biotin↗
PubMed2004

DNA nanotubes self-assembled from triple-crossover tiles as templates for conductive nanowires.

DNA-based nanotechnology is currently being developed as a general assembly method for nanopatterned materials that may find use in electronics, sensors, medicine, and many other fields. Here we present results on the construction and characterization of DNA nanotubes, a self-assembling superstructure composed of DNA tiles. Triple-crossover tiles modified with thiol-containing double-stranded DNA stems projected out of the tile plane were used as the basic building blocks. Triple-crossover nanotubes display a constant diameter of approximately 25 nm and have been observed with lengths up to 20 microm. We present high-resolution images of the constructs, experimental evidence of their tube-like nature as well as data on metallization of the nanotubes to form nanowires, and electrical conductivity measurements through the nanowires. DNA nanotubes represent a potential breakthrough in the self-assembly of nanometer-scale circuits for electronics layout because they can be targeted to connect at specific locations on larger-scale structures and can subsequently be metallized to form nanometer-scale wires. The dimensions of these nanotubes are also perfectly suited for applications involving interconnection of molecular-scale devices with macroscale components fabricated by conventional photolithographic methods.

Base Sequence↗
PubMed2003

DNA-templated self-assembly of protein arrays and highly conductive nanowires.

A DNA nanostructure consisting of four four-arm junctions oriented with a square aspect ratio was designed and constructed. Programmable self-assembly of 4 x 4 tiles resulted in two distinct lattice morphologies: uniform-width nanoribbons and two-dimensional nanogrids, which both display periodic square cavities. Periodic protein arrays were achieved by templated self-assembly of streptavidin onto the DNA nanogrids containing biotinylated oligonucleotides. On the basis of a two-step metallization procedure, the 4 x 4 nanoribbons acted as an excellent scaffold for the production of highly conductive, uniform-width, silver nanowires.

Biotinylation↗