Biomedical subjects

Tae-Woo Lee

Publications and source records attributed to Tae-Woo Lee.

5 recordsLinked to original sources

PubMed2006

Quantitative multispectral biosensing and 1D imaging using quasi-3D plasmonic crystals.

We developed a class of quasi-3D plasmonic crystal that consists of multilayered, regular arrays of subwavelength metal nanostructures. The complex, highly sensitive structure of the optical transmission spectra of these crystals makes them especially well suited for sensing applications. Coupled with quantitative electrodynamics modeling of their optical response, they enable full multiwavelength spectroscopic detection of molecular binding events with sensitivities that correspond to small fractions of a monolayer. The high degree of spatial uniformity of the crystals, formed by a soft nanoimprint technique, provides the ability to image binding events over large areas with micrometer spatial resolution. These features, together with compact form factors, low-cost fabrication procedures, simple readout apparatus, and ability for direct integration into microfluidic networks and arrays, suggest promise for these devices in label-free bioanalytical detection systems.

Avidin↗

PubMed2005

Orientation-averaged light-extinction characteristics of compound particles including aggregate effects.

Orientation-averaged light-extinction characteristics of compound sulfate-carbon-soot particles have been analyzed with a discrete-dipole algorithm (DDSCAT code) for r1/r2 (ratio of primary-particle radius to secondary-particle radius) in the range 7 to 1 and for wavelengths from 0.4 to 0.8 microm. It was found that compound particles above a particle radius of approximately 0.2 microm exhibit light-extinction characteristics that closely match those of a pure sulfate particle. The shielding of the carbon particle by the primary particle apparently reduces the absorption effect of the soot particle over the range of all possible orientations. In light of the fact that soot particles tend to be small in comparison with host sulfate particles, the light-extinction characteristics of compound particles are dictated by the optical properties of the host particles. This result has been applied for aerosol aggregates with log-normal size distributions. For r1/r2 > or = 2 the aggregate extinction coefficient of a group of compound particles remains within 12% of that of a group consisting only of sulfate particles. This allows for effective calculation of the overall aerosol light extinction on the basis of the optical and geometrical properties of the constituent particles without having to include a compound-geometry effect.

Journal Article↗

PubMed2004

Organic light-emitting diodes formed by soft contact lamination.

Although tremendous progress has been made in organic light-emitting diodes (OLEDs), with few exceptions they are fabricated in the standard way by sequentially depositing active layers and electrodes onto a substrate. Here we describe a different approach for building OLEDs, which is based on physical lamination of thin metal electrodes supported by an elastomeric layer against an electroluminescent organic. This method relies only on van der Waals interactions to establish spatially homogeneous, intimate contacts between the electrodes and the organic. We find that devices fabricated in this manner have better performance than those constructed with standard processing techniques. The lamination approach avoids forms of disruption that can be introduced at the electrode/organic interface by metal evaporation and has a reduced sensitivity to pinhole or partial pinhole defects. In addition, because this form of "soft" contact lamination is intrinsically compatible with the techniques of soft lithography, it is easy to build patterned OLEDs with feature sizes into the nanometer regime. This method provides a new route to OLEDs for applications ranging from high performance displays to storage and lithography systems that rely on subwavelength light sources.

Journal Article↗

PubMed2003

Treatment of Cr(VI) and phenol by illuminated TiO2.

Industrial wastewater from organic chemical manufacturing and metal plating industries may contain significant amounts of refractory organic matter and heavy metals. Heavy metals such as Cr(VI) and refractory organic matter like phenol were simultaneously removed by reduction and mineralization, respectively, during photocatalytic process. Therefore, this study was carried out to evaluate the effects of phenol on the removal of Cr(VI) in several environmental conditions. Cr(VI) and phenol were more effectively eliminated in UV/TiO2 condition than either by UV or TiO2-alone. The removal efficiencies of Cr(VI) increased as the pH of the TiO2 slurry decreased, the concentration of phenol increased up to 10 mg L(-1), and nitrogen gas was used. Otherwise, the removal efficiencies of phenol were higher at O2-purged system and neutral pH. Without regard to purging gases, complete Cr(VI) removal was observed at pH 4 after 80 min while 90% phenol destruction and 60% mineralization were found after 120 min. It wasfound that application of photocatalytic reaction by using illuminated TiO2 to treat wastewater containing both Cr(VI) and phenol was possible.

Carcinogens, Environmental↗

PubMed2002

Stoichiometry and structural effect of the cyclic nucleotide binding to cyclic AMP receptor protein.

Cyclic AMP receptor protein (CRP) is a homodimeric protein, which is activated by cAMP binding to function as a transcriptional regulator of many genes in prokaryotes. Until now, the actual number of cAMP molecules that can be bound by CRP in solution has been ambiguous. In this work, we performed a nuclear magnetic resonance study on CRP to investigate the stoichiometry of cyclic nucleotide binding to CRP. A series of (1)H-(15)N heteronuclear single quantum coherence (HSQC) spectra of the protein in the absence and in the presence of cAMP or cGMP were analyzed. The addition of cAMP to CRP induced a biphasic spectral change up to 4 equivalents, whereas the cGMP addition made a monophasic change up to 2 equivalents. Altogether, the results not only established for the first time that CRP possesses two cyclic AMP-binding sites in each monomer, even in a solution without DNA, but also suggest that the syn-cAMP binding sites of the CRP dimer can be formed by an allosteric conformational change of the protein upon the binding of two anti-cAMPs at the N-terminal domain. In addition, a residue-specific inspection of the spectral changes provides some new structural information about the cAMP-induced allosteric activation of CRP.

Allosteric Regulation↗