• Journal of Microbiology
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• v.35 no.3
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• pp.181-187
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• 1997

Filamentous cyanobacteria are an ecologically important group of bacteria because they are able to provide both organic carbon fixed nitrogen that can support the nutritional requirements for other microorganisms. Because of their prokaryotic nature, they can also be used as potentially powerful model systems for the analysis of oxygenic photosynthesis and nitrogen fixation. Gene transfer is an indispensable procedure for genetic analysis of filamentous cyanobacteria. Electroporation was used to introduce foreign DNA into cyanobacterial cells. In experiments designed to optimize the electroporation technique, the effects of the field strength (amplitude of pulse) and time constant (duration of pulse), DNA concentration and host restriction/modification of DNA on the efficiency of electro-transformation were investigated. The results of this research revelaed that a high voltage pulse of short duration was effective for the electro-transformation of Anabaene sp. M131. The maximal number of transformants was obtained at 6 kV/cm with a pulse duration of 5 msec. The efficiency of electro-transformation was also sensitive to concenetration of DNA; even small amounts of DNA (0.01 .mu.g/ml) were able to gie a large number of transformants (1.0 * 10$\^$3/ cfu/ml).

• Journal of the Korean Chemical Society
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• v.29 no.5
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• pp.533-538
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• 1985

To investigate the importance of the hydrophobic interaction in the spermine-induced collapse of DNA to a compact structure, the effect of urea on the anomalous absorbance-temperature profile of calf thymus DNA has been investigated. With the increase of the urea concentration, the trough phase of the anomalous absorbance-temperature profile was eliminated eventually. The cooperativity, enthalpy, and the midpoint of the transition to the trough region are more sensitive to urea than those of the Tm-region transition. The present data of the adverse effect of urea, a hydrophobic environmental reagent, on the thermal stabilization of the condensed state of DNA, suggest that hydrophobic interaction may play an important role in the stabilization of the tertiary structure of the collapsed state of DNA.

• Bulletin of the Korean Chemical Society
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• v.28 no.12
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• pp.2329-2332
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• 2007

Salsolinol, endogenous neurotoxin, is known to be involved in the pathogenesis of Parkinson's disease (PD). In the present study, we have investigated the oxidative damage of DNA induced by the reaction of salsolinol with Cu,Zn-SOD. When plasmid DNA incubated with salsolinol and Cu,Zn-SOD, DNA cleavage was proportional to the concentrations of salsolinol and Cu,Zn-SOD. The salsolinol/Cu,Zn-SOD system-mediated DNA cleavage was significantly inhibited by radical scavengers such as mannitol, ethanol and thiourea. These results indicated that free radicals might participate in DNA cleavage by the salsolinol/Cu,Zn-SOD system. Spectrophotometric study using a thiobarbituric acid showed that hydroxyl radical formation was proportional to the concentration of salsolinol and was inhibited by radical scavengers. These results indicated that hydroxyl radical generated in the reaction of salsolinol with Cu,Zn-SOD was implicated in the DNA cleavage. Catalase and copper chelators inhibited DNA cleavage and the production of hydroxyl radicals. These results suggest that DNA cleavage is mediated in the reaction of salsolinol with Cu,Zn-SOD via the generation of hydroxyl radical by a combination of the oxidation reaction of salsolinol and Fenton-like reaction of free copper ions released from oxidatively damaged SOD.

• Archives of Pharmacal Research
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• v.27 no.12
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• pp.1263-1269
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• 2004

The objective of this study was to characterize immunoliposomes carrying plasmid DNA with optimal encapsulation efficiency and antibody density. Plasmid DNA was encapsulated by the freezing/thawing method into liposomes composed of POPC (1-palmitoyl-2-oleoyl-sn-glycerol- 3-phosphocholine), DDAB (didodecyl dimethyl ammonium bromide), DSPE-PEG 2000 (distearoyl phosphatidyl ethanolamine polyethylene glycol 2000) and DSPE-PEG 2000-maleimide. The liposomes carrying plasmid DNA were extruded through two stacked polycarbonate filters, of different pore size, to control the liposome size. Then, rat IgG molecules were conjugated to the liposomes. The immunoliposomes containing plasmid DNA were separated from the free plasmid DNA and unconjugated IgG by Sepharose CL-4B column chromatography. The DNA amount encapsulated was affected by DDAB (cationic lipid) concentration, the initial amount of plasmid DNA between 10 ${\mu}g$ and 200 ${\mu}g$, the total lipid amount and plasmid DNA size, but not significantly by liposome size. By varying the ratio of DSPE-PEG 2000-maleimide to IgG, the number of IgG molecules per liposome was changed significantly.

• Bulletin of the Korean Chemical Society
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• v.35 no.10
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• pp.3015-3020
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• 2014

The behavior of benzo[a]pyrene-7,8-dione (BPQ) in aqueous solution and its interaction with native DNA was investigated using conventional absorption and linear dichroism (LD) spectroscopy. The appearance of a broad absorption maximum at long wavelengths and its proportional relationship to solvent polarizability suggested that BPQ adopts a aggregated state for all solutions examined. Disappearance of this absorption band at higher temperatures in aqueous solution also supported BPQ aggregation. When associated with DNA absorption spectral properties were essentially the same as that in aqueous solution. However, two isosbestic wavelengths were found in the concentration-dependent absorption spectrum of the BPQ-DNA complex, suggesting the presence of at least two or more DNA-bound BPQ species. Both species produced $LD^r$ spectra whose magnitude in BPQ absorption region is larger or comparable to that in the DNA absorption region, suggesting that the molecular BPQ plane is near perpendicular relative to the local DNA helical axis. Therefore, BPQ molecules are aligned along the DNA stem in both DNA-aggregated BPQ species.

• YAKHAK HOEJI
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• v.54 no.1
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• pp.32-38
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• 2010

The aim of this study was to evaluate the effect of galangin towards hydrogen peroxide-induced DNA damage. The calf thymus DNA and Chinese Hamster Lung (CHL) cells were used to measure 8-hydroxy-2'-deoxyguanosine(8-OH2'dG) as an indicator of DNA oxidative damage using high performance liquid chromatography with electrochemical detection. Hydrogen peroxide in the presence of Fe(II) ion induced the formation of 8-OH2'dG in both calf thymus DNA and CHL cells. The DNA damage effects were enhanced by increasing the concentration of Fe(II) ion and inhibited by galangin. In the single cell gel electrophoresis (Comet assay), galangin and dl-a-tocopherol showed an inhibitory effect in CHL on hydrogen peroxide induced DNA single strand breaks. Galangin showed more potent activity than dl-$\alpha$-tocopherol under our experimental conditions. These results indicate that galangin can modify the action mechanisms of the oxidative DNA damage and may act as chemopreventive agents against oxidative stress.

• Bulletin of the Korean Chemical Society
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• v.12 no.3
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• pp.262-264
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• 1991

An anomalous absorbance-temperature profile of calf thymus DNA, having a hypochromic trough just before the rise the $T_m$-region phase, occurs at the spermine concentration where the DNA collapses into a compact structure. The trough phase can be eliminated by the addition of ethidium bromide and also by a hydrophobic environment.

• The Journal of the Acoustical Society of Korea
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• v.26 no.1
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• pp.42-47
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• 2007

In this paper. we have studied improvement in sensitivity by increasing the frequency of SAW sensors for detecting the immobilization and hybridization of DNA. The sensor consists of twin SAW delay lines operating at 200MHz, a sensing channel and a reference channel. fabricated on $36^{\circ}$ rotated Y-cut X-propagation $LiTaO_3$ crystals. The optimum concentration of probe and target DNA was decided for the improvement of detection mechanism. and digital syringe pump system was used to reduce the human errors. The hybridization between immobilized probe DNA and target DNA on the gold-coated delay line results in mass loading on the delay line of the sensing channel. Thus, the relative frequency change was monitored in relation to the mass loading. The measurement results showed a good response of the sensor to the DNA hybridization with a maximum sensitivity level up to 0.066ng/m1/Hz.

• Archives of Pharmacal Research
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• v.27 no.8
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• pp.829-833
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• 2004

The bioactivity-guided fractionation of the methylene chloride extract of the sclerotium of Poria cocos led to the isolation of (S)-(＋)-turmerone (1), ergosterol peroxide (2), polyporenic acid C (3), dehydropachymic acid (4), pachymic acid (5), and tumulosic acid (6). Compounds 4-6 exhibited moderate cytotoxicities, with $IC_{50}$ values of 20.5, 29.1, and $10.4{\;}\mu\textrm{m}$, respectively, against a human colon carcinoma cell line. However, 3-6 not only showed inhibitory activities as potent as etoposide used as a positive control on DNA topoisomerase II (36.1, 36.2, 43.9 and 66.7％ inhibition at a concentration of $20{\;}\mu\textrm{m}$, respectively), but also inhibition of DNA topoisomerase I (55.8, 60.7, 43.5, and 83.3％ inhibition at a concentration of $100{\;}\mu\textrm{m}$, respec-tively).

• JSTS:Journal of Semiconductor Technology and Science
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• v.14 no.2
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• pp.153-162
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• 2014

We show that carbon nanotube sensors with gold particles on the single-walled carbon nanotube (SWNT) network operate as Schottky barrier transistors, in which transistor action occurs primarily by varying the resistance of Au-SWNT junction rather than the channel conductance modulation. Transistor characteristics are calculated for the statistically simplified geometries, and the sensing mechanisms are analyzed by comparing the simulation results of the MOSFET model and Schottky junction model with the experimental data. We demonstrated that the semiconductor MOSFET effect cannot explain the experimental phenomena such as the very low limit of detection (LOD) and the logarithmic dependence of sensitivity to the DNA concentration. By building an asymmetric concentric-electrode model which consists of serially-connected segments of CNTFETs and Schottky diodes, we found that for a proper explanation of the experimental data, the work function shifts should be ~ 0.1 eV for 100 pM DNA concentration and ~ 0.4 eV for $100{\mu}M$.