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Hyun Jin Hwang

Publications and source records attributed to Hyun Jin Hwang.

10 recordsLinked to original sources
PubMed2006

The photodissociation reaction dynamics of CF(3)I at 304 nm ((3)Q(0+), (1)Q(1)<--(3)Q(0+), and (3)Q(1)).

The photodissociation of CF(3)I at 304 nm has been studied using long time-delayed core-sampling photofragment translational spectroscopy. Due to its capability of detecting the kinetic energy distribution of iodine fragments with high resolution, it is able to directly assign the vibrational state distribution of CF(3) fragments. The vibrational state distributions of CF(3) fragments in the I(*)((2)P(12)) channel, i.e., (3)Q(0+) state, have a propensity of the nu(2) (') umbrella mode with a maximum distribution at the vibrational ground state. For the I((2)P(32)) channel, i.e., (1)Q(1)<--(3)Q(0+), the excitation of the nu(2) (') umbrella mode accounts for the majority of the vibrational excitation of the CF(3) fragments. The 1 nu(1) (') (symmetric CF stretch) +nnu(2) (') combination modes, which are associated with the major progression of the nu(2) (') umbrella mode, are observed for the photodissociation of CF(3)I at the I channel, i.e., (3)Q(1) state. The bond dissociation energy of the CI bond of CF(3)I is determined to be D(0)(CF(3)-I)</=53.62+/-0.5 kcalmol (18 754+/-175 cm(-1)) by applying the energy conservation law to the photodissociation process.

Journal Article↗
PubMed2006

State-to-state correlated study of CD3I photodissociation at 266 and 304 nm.

High-resolution photofragment translational spectroscopy is used in this work to measure the translational and internal energy distributions in the CD3 and iodine fragments produced from the photodissociation of CD3I at 266 and 304 nm. Channel selected detection, via resonantly enhanced multiphoton ionization, combined with one-dimensional core sampling provides detailed information about vibrational state distributions of the CD3 fragments. The vibrational state distributions of CD3 fragments in the I*(2P12) channel have a propensity of nu2 ' umbrella bending mode with a maximum at nu2 ' = 1 for 266 nm photodissociation. For I*(2P12) channel at 304 nm photodissociation, vibrational state distributions of CD3 fragment have a maximum in the vibrational ground state. For the I(2P32) channel (1Q1 <-- 3Q(0+)), nu2 ' umbrella bending vibrational distribution is measured as the predominant vibrational mode but has a much broader distribution when compared to that of the I* channel. The vibrational state distributions of the CD3 fragment produced from the perpendicular transition, i.e., 3Q1, which was determined at 304 nm photodissociation, has a maximum at nu2 ' = 1. The curve crossing possibility between the 1Q1 and 3Q(0+) adiabatic potentials is determined as 0.19 for 266 and 0.85 for 304 nm. The trend in reaction dynamics in 266 and 304 nm photodissociation of CD3I is compared with theoretical calculations. A bond dissociation energy D0(C-I) = 56.60+/-0.5 kcal/mol was derived by applying laws of energy conservation.

Chemistry, Physical↗
PubMed2005

State-to-state reaction dynamics of CH3I photodissociation at 304 nm.

The detailed reaction dynamics of CH(3)I photodissociation at 304 nm were studied by using high-resolution long time-delayed core-sampling photofragment translation spectroscopy. The vibrational state distributions of the photofragment, i.e., CH(3), are directly resolved due to the high kinetic resolution of this experiment for the first time. CH(3) radicals produced from I((3)Q(0+)), I((1)Q(1) <--( 3)Q(0+)), and I((3)Q(1)) channels are populated in different vibrational state distributions. The I((3)Q(0+)) and I((3)Q(1)) channels show only progressions in the nu2'(a2") umbrella bending mode, and the I((1)Q(1) <-- (3)Q(0+)) channel shows both progression in the nu2' umbrella bending mode and a small amount of excitation in the nu1'(a1') C-H stretching mode. The photodissociation processes from the vibrational hot band of CH(3)I (upsilon3 = 1, upsilon3 = 2) were also detected, primarily because of the absorption probability from the vibrational excited states, i.e., hot bands are relatively enhanced. Photofragments from the hot bands of CH(3)I show a cold vibrational distribution compared to that from the vibrational ground state of CH(3)I. The I* quantum yield and the curve crossing possibility were also studied for the ground vibrational state of CH(3)I. The potential energy at the curve crossing point was calculated to be 32 790 cm(-1) by using the one-dimensional Landau-Zener model.

Journal Article↗
PubMed2004

Antioxidant and anticancer activity of extract from Betula platyphylla var. japonica.

The antioxidant and anticancer properties of a medicinal plant, Betula platyphylla var. japonica were investigated. The total methanol extract of B. platyphylla var. japonica had protective effects against hydrogen peroxide (H2O2) in the Chinese hamster lung fibroblast (V79-4) cell line and induced apoptotic cell death in human promyelocytic leukemia (HL-60) cells, a cancer cell line. B. platyphylla var. japonica extract significantly increased cell viability against H2O2. The extract also showed high 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity (IC50 2.4 microg/ml) and lipid peroxidation inhibitory activity (IC50 below 4.0 microg/ml). Furthermore, B. platyphylla var. japonica extract reduced the number of V79-4 cells arrested in G2/M in response to H2O2 treatment and increased the activities of several cellular antioxidant enzymes, including superoxide dismutase, catalase and glutathione peroxidase. Treatment with B. platyphylla var. japonica extract induced cytotoxicity and apoptosis in HL-60 cells, as shown by nucleosomal DNA fragmentation, increases in the subdiploid cell population, and fluorescence microscopy. B. platyphylla var. japonica extract gradually increased the expression of pro-apoptotic Bax and led to the activation of caspase-3 and cleavage of PARP. These findings suggest that B. platyphylla var. japonica exhibits potential antioxidant and anticancer properties.

Animals↗
PubMed2004

Construction of a pTOC-T vector using GST-ParE toxin for direct cloning and selection of PCR products.

Using linker insertion mutations, we determined the most stable region of the parE gene which encodes a toxic protein (ParE) that inhibits growth of Escherichia coli. The toxicity of ParE was sustained until a 144 bp linker was inserted into this region. We have developed a 3' T-overhang vector based on these characteristics of the GST-ParE toxin, and named pTOC-T. Because pTOC-T uses a post-segregational killing system, all transformants grown up on the plates can be considered as recombinants containing foreign DNA. pTOC-T not require X-Gal, IPTG or other substrates for selection. This T-vector using a positive selection system can be applied to various E. coli strains such as XL1-Blue, BL21, DH5alpha, JM109, and JM110.

Bacterial Toxins↗
PubMed2003

Screening of medicinal plant extracts for antioxidant activity.

The methanol extracts of nine medicinal plants traditionally used in Chinese medicine were screened for antioxidant activity versus resveratrol, which has been shown to protect cells from oxidative damage [Toxicol. Lett. 102 (1998) 5]. Most of the plant extracts used in this study inhibited the H(2)O(2)-induced apoptosis of Chinese hamster lung fibroblast (V79-4) cells. The extracts of Areca catechu var. dulcissima, Paeonia suffruticosa, Alpinia officinarum, Glycyrrhiza uralensis and Cinnamomun cassia strongly enhanced viability against H(2)O(2)-induced oxidative damage in V79-4 cells. Relatively high levels of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity were detected in extracts of Areca catechu var. dulcissima, Paeonia suffruticosa and Cinnamomun cassia (IC(50) < 6.0 microg/ml). The activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX) were dose-dependently enhanced in V79-4 cells treated with most of the plant extracts. The extracts of Areca catechu var. dulcissima showed higher antioxidant activity than resveratrol in all experiments. These results suggest that the plant extracts prevent oxidative damage in normal cells probably because of their antioxidant characteristics.

Animals↗
PubMed2003

Antioxidant activity of extracts from Alpinia katsumadai seed.

Alpinia katsumadai (Zingiberaceae) has been widely used in traditional Chinese medicine to treat a variety of conditions such as emesis and gastric disorders. However, very little is known about the cellular actions by which this plant mediates its therapeutic effects. Various aspects of antioxidant activity were evaluated in a total extract derived from Alpinia katsumadai seed in this study. Relatively high levels of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity were detected in the total extract (IC(50) 1.6 microgram/mL). Other known compounds such as (-)-epigallocatechine-3-gallate (EGCG) and resveratrol showed IC(50) values of <0.8 and 4.8 microgram/mL, respectively. The total extract also enhanced the viability of Chinese hamster lung fibroblast (V79-4) cells and inhibited H(2)O(2)-induced apoptosis. The total extract of Alpinia katsumadai also dose-dependently enhanced the activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX) in V79-4 cells, and these effects were comparable to other antioxidant compounds such as EGCG and resveratrol. Taken together, our findings show that Alpinia katsumadai contains significant antioxidant activity.

Alpinia↗
PubMed2002

Solid-phase genetic engineering with DNA immobilized on a gold surface.

A novel method for immobilizing large DNA fragments on a solid surface was developed. A mixed self-assembled monolayer of thiolated single-stranded DNA with inert alkanethiol was generated on a gold (Au) surface through the Au-S reaction. Surface-tethered DNA generated by this method was compatible with various genetic engineering techniques, including hybridization, polymerization, restriction enzyme digestion and ligation. Kinetic control of surface coverage of immobilized DNA was critical for optimizing genetic engineering techniques on solid-phase. Multi-step reaction schemes utilizing various genetic engineering techniques described above were employed for solid-phase gene assembly. We were able to immobilize DNA fragments of up to 1180 bp on a solid surface. Furthermore, we showed that these immobilized genes can be regenerated by PCR. The present work suggests that these types of assembled genes can be used to store and regenerate genes on solid-phase.

Base Sequence↗
PubMedDate not supplied

Induction of apoptosis by momordin I in promyelocytic leukemia (HL-60) cells.

We studied the effect of momordin I, a compound purified from a plant, Ampelopsis japonica, on cell proliferation and induction of apoptosis in human promyelocytic leukemia (HL-60) cells. Momordin I was cytotoxic to HL-60 cells with an IC50 of 19.0 microg/ml. The antiproliferative effects of momordin I appear to be attributable to its induction of apoptotic cell death, as momordin I induced nuclear morphology changes and internucleosomal DNA fragmentation and it increased the proportion of hypodiploid cells. Momordin I treatment also gradually decreased the expression of.the anti-apoptotic protein Bcl-2, but increased the expression of the pro-apoptotic protein Bax. In addition, momordin I treatment increased the activation of caspase-3 and cleavage of poly (ADP-ribose) polymerase. In this study we showed that momordin I induced apoptosis of HL-60 cells by reduction of the Bcl-2:Bax ratio and by activation of caspase-3. These results provide important information towards understanding the mechanism by which momordin I induces apoptosis.

Apoptosis↗