PubMed Health⌕ Search

Biomedical subjects

Joon Won Park

Publications and source records attributed to Joon Won Park.

14 recordsLinked to original sources
PubMed2006

Nanoscale controlled self-assembled monolayers and quantum dots.

Self-assembled monolayer (SAM) and fluorescent quantum dots (QDs) share common ground as emerging tools for nanoscale observation of biological interactions. SAMs provide excellent means of controlling the surface characteristics through individually tailored and engineered building blocks. SAMs on various surfaces have demonstrated clear advantages over uncontrolled multilayer films in fabricating electrochemical sensor, optical sensor, chemical biosensor, and atomic force microscopy. Similarly, QDs have advantages over organic fluorophores in long-term and real-time optical imaging of biological specimens. QDs conjugated with various biomolecules have been successfully applied to bioimaging, biosensing and cell encoding.

Animals↗
PubMed2006

Sensitivity enhancement of DNA microarray on nano-scale controlled surface by using a streptavidin-fluorophore conjugate.

High throughput analysis of DNA in low concentration and small volume is an important issue and a continuing challenge in the field of DNA microarray and sensor. Recently, we have demonstrated that the DNA microarray on nano-scale controlled surface provides ample space for hybridization resulting in the best discrimination efficiency for SNP analysis. Here, we report the utility of the nano-scale controlled surface in conjunction with a multiply tagged protein. Application of streptavidin-fluorophore conjugates in combination with the highly controlled surface that suppresses non-specific binding of DNA allows highly sensitive detection of DNA while maintaining superior SNP discrimination efficiency comparable to our earlier results. The sensitivity of DNA microarray on the mesospaced surface is two orders of magnitude higher than that of the generic surface when a streptavidin-fluorophore conjugate was employed, and the detection limit on the former surface was found to be 50 fM of 15-mer target DNA. Various streptavidin-fluorophore conjugates including streptavidin-Cy3, streptavidin-Cy5, streptavidin-Alexa Flour 555 and streptavidin-phycoerythrin were examined.

Anthracenes↗
PubMed2006

Self-assembly of a diblock copolymer on a patterned surface with low-energy electron beam.

A pattern was generated by 500 eV electron beam irradiation on benzaldimine monolayer through a grid and subsequent hydrolysis of nonirradiated regions. While we tried to assemble a block copolymer, polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP), on the pattern, we observed that the polarity difference between the two different regions was not right for discriminating the wetting behavior of two blocks of the polymer. Among various modifications of the retrieved amine, it was found that tribromoacetaldehyde was suitable for this end. Surprisingly, treatment of the aldehyde gave a surface preferring the polystyrene block to poly(4-vinylpyridine) block, while the irradiated section favored the latter block. As a result, island morphology was observed on the tribromoacetaldimine region and hole morphology on the irradiated region when the film thickness was 1.3Lo. Contact angle data were consistent with the observed symmetric wetting on the former region and the asymmetric one on the latter.

Journal Article↗
PubMed2006

Surface modification for DNA and protein microarrays.

Microarrays of biomolecules are emerging as powerful tools for genomics, proteomics, and clinical assays, since they make it possible to screen biologically important binding events in a parallel and high throughput fashion. Because the microarrays are fabricated on a solid support, coating of the surface and immobilization strategy of the biomolecules are major issues for successful microarray fabrication. This review deals with both DNA microarrays and protein microarrays, and focuses on the various modification approaches for the two-dimensional surface materials and three-dimensional ones. In addition, the immobilization strategies including adsorption, covalent attachment, physical entrapment, and affinity attachment of the biomolecules are summarized, and advantage and limitation of representative efforts are discussed.

Manufactured Materials↗
PubMed2005

DNA microarrays on nanoscale-controlled surface.

We have developed new surface to ensure a proper spacing between immobilized biomolecules. While DNA microarray on this surface provided each probe DNA with ample space for hybridization with incoming target DNAs, the microarray showed enhanced discrimination efficiency for various types of single nucleotide polymorphism. The high discrimination efficiency holds for all tested cases (100:<1 for internal mismatched cases; 100:<28 for terminal mismatched ones). In addition, by investigating influence of hybridization temperature and washing condition on the fluorescence intensity and the discrimination efficiency with and without controlled mesospacing, it was observed that the nanoscale-controlled surface showed good discrimination efficiency in a wide range of temperature (37-50 degrees C), and hybridization behavior on the surface was in agreement with the solution one. Intriguingly, it was found that washing process after the hybridization was critical for the high discrimination efficiency. For the particular case, washing process was so efficient that only 30 s washing was sufficient to reach the optimal discrimination ratio.

Anthracenes↗
PubMed2005

DNA microarrays on a dendron-modified surface improve significantly the detection of single nucleotide variations in the p53 gene.

Selectivity and sensitivity in the detection of single nucleotide polymorphisms (SNPs) are among most important attributes to determine the performance of DNA microarrays. We previously reported the generation of a novel mesospaced surface prepared by applying dendron molecules on the solid surface. DNA microarrays that were fabricated on the dendron-modified surface exhibited outstanding performance for the detection of single nucleotide variation in the synthetic oligonucleotide DNA. DNA microarrays on the dendron-modified surface were subjected to the detection of single nucleotide variations in the exons 5-8 of the p53 gene in genomic DNAs from cancer cell lines. DNA microarrays on the dendron-modified surface clearly discriminated single nucleotide variations in hotspot codons with high selectivity and sensitivity. The ratio between the fluorescence intensity of perfectly matched duplexes and that of single nucleotide mismatched duplexes was >5-100 without sacrificing signal intensity. Our results showed that the outstanding performance of DNA microarrays fabricated on the dendron-modified surface is strongly related to novel properties of the dendron molecule, which has the conical structure allowing mesospacing between the capture probes. Our microarrays on the dendron-modified surface can reduce the steric hindrance not only between the solid surface and target DNA, but also among immobilized capture probes enabling the hybridization process on the surface to be very effective. Our DNA microarrays on the dendron-modified surface could be applied to various analyses that require accurate detection of SNPs.

Anthracenes↗
PubMed2005

Nanoscale-controlled spacing provides DNA microarrays with the SNP discrimination efficiency in solution phase.

We have prepared solid substrates modified with a cone-shaped dendron that generates mesospacing (3.2 nm on average) on the surface. This nanoscale-controlled surface provided an ideal DNA microarray in which each probe DNA strand was given ample space for the incoming target DNA, resulting in selectivity as high as that in solution (100: < 1). In addition, high hybridization yield confirms that DNA probes on the mesospaced surface are sterically unhindered for the hybridization.

Base Sequence↗
PubMed2005

Pattern formation through selective chemical transformation of self-assembled benzaldimine monolayer by soft X-ray irradiation.

Benzaldimine monolayer was exposed to soft X-rays, and the involved chemical transformation was investigated using X-ray photoelectron spectra and near-edge X-ray absorption fine structure spectroscopy. The spectroscopy indicated that irradiation of soft X-ray (550 eV)-induced selective transformation of the imine group into a nonhydrolyzable one, i.e., the amine group. Utilizing the selective chemical transformation of the imine group with the soft X-ray irradiation, we were able to generate a micropattern. AFM images showed that the patterning with alternating surface topology was effective. The patterned monolayer was further modified with biotin and Cy3-tagged Streptavidin sequentially. Fluorescence images showed that the above molecules were selectively immobilized onto the amine-terminated region of the patterned surface. The current system is found to be more efficient than the predecessor, 4-nitrobenzaldimine monolayer.

Imines↗
PubMed2004

Modification of indium-tin oxide (ITO) glass with aziridine provides a surface of high amine density.

The surface of indium-tin oxide (ITO) substrates was successfully modified with aziridine. Modification of the surface was achieved through facile ring-opening, and hyperbranching polymerization of the ring-strained heterocycle initiated from the reactive group on the surface. Amine density of the aziridine-modified ITO measured with UV-vis spectrophotometry is 10 amines/nm2. Cyclic voltammetric analysis showed that the aziridine-modified electrode was less active for Ru(NH3)6(3+) in comparison with the pristine electrode, while no difference was observed for Fe(CN)6(4-). Electrochemical impedance spectroscopic experiments unveiled that the modified electrode was more efficient for electron transfer to the latter species than to the former.

Amines↗
PubMed2003

Hyperbranching polymerization of aziridine on silica solid substrates leading to a surface of highly dense reactive amine groups.

Silica solid substrates such as fused silica, silicon wafers with a natural oxide layer, and glass were treated with aziridine to produce reactive primary amine groups on the top surface. We found that the hydroxyl group on the substrate was able to initiate the ring-opening polymerization of aziridine, resulting in highly branched poly(ethyleneimine) on the surface. In dichloromethane, the thickness of the organic film reached 25 A in 20 h and the absolute density of the primary amine group on the surface was 23 amines/nm(2). Atomic force microscopy shows an embossed morphology after the polymerization in dichloromethane, while use of toluene gives a rather smooth surface. The resulting organic layer shows high thermal and pH stability.

Journal Article↗
PubMed2002

Anomalously high cooperativity of oligodeoxycytidylic acid for luminescence resonance energy transfer to lanthanide ions.

The luminescence of terbium(III) and europium(III) through luminescence resonance energy transfer from mononucleotides and oligodeoxynucleotides is examined. Among mononucleotides, dGMP gives the strongest luminescence of terbium(III), while dTMP and dCMP yield a luminescence intensity of europium(III) that is larger than the other two cases. In the homodeoxydecamers, decadeoxycytidylic acid (dC10) produces the highest intensity for both metals. The anomalously large cooperativity of dC10 is explained by the easiness of deformation of the helical structure to bind lanthanide ions, and a circular dichroism study supports this explanation.

Circular Dichroism↗
PubMed1996

Catalytic Hydrolysis of Phosphate Diesters by Lanthanide(III) Cryptate (2.2.1) Complexes.

Lanthanide(III) Cryptate (2.2.1) chlorides (Ln(2.2.1)Cl(3); Ln = La (1a), Ce(1b), and Eu(1c); (2.2.1) = 4,7,13,16,21-pentaoxa-1,10-diazabicyclo[8.8.5]tricosane) are effective for the catalytic hydrolysis of bis(4-nitrophenyl) phosphate. Kinetic studies reveal that the europium(III) complex (1c) catalyzes the hydrolysis to produce 6 equiv of 4-nitrophenol with a significant rate (k(1) = 1.5 x 10(-)(4) s(-)(1) at 0.40 mM) at pH 8.5 and 50 degrees C. The catalytic activity of the complexes is increased with decreasing the ionic size, i.e, La < Ce < Eu. While the use of hydrogen peroxide further increase the activity of 1b (k(1) = 1.6 x 10(-)(3) s(-)(1) at 0.40 mM), the presence of molecular oxygen does not affect the activity at all. Crystal of 1a.CH(3)OH([La(2.2.1)(Cl)(2)](Cl)(CH(3)OH)) belongs to the space group Pnma with a = 17.072(3) Å, b = 19.037(3) Å, c = 14.725(2) Å, V = 4786(1) Å(3), Z = 8, D(x)() = 1.691 g cm(-)(3), &mgr; = 21.7 cm(-)(1). The encryptated metal ion is nine-coordinated, and all the heteroatoms of the cryptate (2.2.1) ligand coordinate the metal center to form a bowl-shaped structure. Two coordinating chloride anions are located on the open face with a cis geometry. The existence of coordinated water to the europium(III) complex 1c in the aqueous solution was confirmed by time-resolved Eu(III) luminescence spectroscopy. From the decay constants in H(2)O and D(2)O, the numbers of coordinated water molecules (q) are found to be 3.02 at pH of 5.0. The above kinetic and spectroscopic observation are supportive of mechanisms in which the metal complexes act as a center for binding and activation as well as a source of nucleophilic metal hydroxides.

Journal Article↗