Biomedical subjects

Han-Seung Jeong

Publications and source records attributed to Han-Seung Jeong.

3 recordsLinked to original sources

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↗

PubMed2002

Chaperonin GroESL mediates the protein folding of human liver mitochondrial aldehyde dehydrogenase in Escherichia coli.

An efficient bacterial expression system for the human mitochondrial aldehyde dehydrogenase (ALDH2) was developed using co-overexpression of heat shock chaperone gene GroESL. On the basis of the ALDH2 amino acid sequence and cDNA sequences a full-length cDNA encoding wild-type ALDH2 was cloned from a human liver library. A mutant-type ALDH2 (ALDH2(2)) was developed using site-directed mutagenesis of the ALDH2 cDNA and also cloned. Both types of ALDH2 cDNA were subcloned for expression in Escherichia coli (E. coli), recombinant ALDH2 and ALDH2(2) were successfully expressed as soluble active enzymes following co-expression with a second plasmid construct producing GroES and GroEL, E. coli chaperonin proteins. Purified wild-type ALDH2 and mutant ALDH2(2) had a K(m) for acetaldehyde of 0.65 and 25.73 microM, respectively. Co-expression of ALDH2 with ALDH2(2) in the presence of E. coli chaperonins produced a soluble enzyme with a K(m) for acetaldehyde of 8.79 microM, suggesting that the product was a heteromer. Mitochondrial matrix hsp60 and hsp10 chaperonins are then thought to act on imported ALDH2 and are essential for accurate protein folding and multisubunit formation. Protein-protein interactions between ALDH2s and various chaperones were investigated using the yeast two-hybrid system. The wild-type and mutant-type enzymes strongly interacted with each other and GroEL and ALDH2s also interacted but only weakly. Chaperone hsp10 also interacted with hsp60 and ALDH2(1) and ALDH2(2), but again the interactions were weak ones.

Aldehyde Dehydrogenase↗

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↗