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A Comparative Study of the Anti-Platelet Effects of cis- and trans-Resveratrol
( Hwa Kim ),( Seok Jeong Oh ),( Ying Qiu Liu ),( Moo Yeol Lee ) 한국응용약물학회 2011 Biomolecules & Therapeutics(구 응용약물학회지) Vol.19 No.2
Although various biological activities of resveratrol have been extensively studied, most reports have focused on trans-resveratrol and little attention has been paid to the cis-isomer. In this study, the effect of cis-resveratrol on platelet activity was examined and compared with that of the trans-isomer. Treatment with cis-resveratrol resulted in inhibition of platelet aggregation induced by thrombin, collagen or ADP, which are representative aggregation-inducing agents, and the trans-isomer elicited the same effects. These effects were concentration-dependent in the range of 1-100 μM. However, the potency of the cis-isomer was much lower than that of the trans-isomer; the IC50 values for the cis-isomer versus the trans-isomer were 31 ± 12 vs 15 ± 3, 16 ± 3 vs 9 ± 4, and 60 ± 15 vs 25 ± 6 μM for thrombin-, collagen- and ADP-induced aggregation, respectively. These results indicate that cis-resveratrol has a less potent anti-platelet activity, compared with the trans-isomer, and raise the possibility that the biological activities of the cis-isomer may be different from those of the trans-isomer. It will be necessary to evaluate the activity of cis-resveratrol independently of the trans-isomer.
Biocompatible Dispersion Methods for Carbon Black
Hwa Kim,Kwangsik Park,Moo-Yeol Lee 한국독성학회 2012 Toxicological Research Vol.28 No.4
The biological activity of particles is largely dependent on their size in biological systems. Dispersion in the aqueous phase has been both a critical impediment to and a prerequisite for particle studies. Carbon black has been used as a surrogate to investigate the biological effects of carbonaceous particles. Here, biocompatible methods were established to disperse carbon black into ultrafine and fine particles which are generally distinguished by the small size of 100 nm. Carbon black with a distinct particle size, N330 and N990 were suspended in blood plasma, cell culture media, Krebs-Ringer’s solution (KR), or physiological salt solution (PSS). Large clumps were observed in all dispersion preparations; however, sonication improved dispersion - averaged particle sizes for N330 and N990 were 85.0 ± 42.9 and 112.4 ± 67.9 nm, respectively, in plasma; the corresponding sizes in culture media were 84.8 ± 38.4 and 164.1 ± 77.8 nm. However, sonication was not enough to disperse N330 less than 100 nm in either KR or PSS. Application of Tween 80 along with sonication reduced the size of N330 to less than 100 nm, and dispersed N990 larger than 100 nm (73.6 ± 28.8 and 80.1 ± 30.0 nm for N330 and 349.5 ± 161.8 and 399.8 ± 181.1 nm for N990 in KR and PSS, respectively). In contrast, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) exhibited little effect. Electron microscopy confirmed the typical aciniform structure of the carbon arrays; however, zeta potential measurement failed to explain the dispersibility of carbon black. The methods established in this study could disperse carbon black into ultrafine and fine particles, and may serve as a useful model for the study of particle toxicity, particularly size-related effects.
Polygalacturonase의 활성 증진 및 이를 이용한 식물 단세포 제조 방법
김혁화(Hyuk?Hwa Kim) 한국식품영양과학회 2007 한국식품영양과학회지 Vol.36 No.12
본 연구에서는 효소의 활성을 증진시킬 수 있는 새로운 방법의 개발을 위하여 미생물로부터 분리, 정제된 polygalacturonase(PGase)에 xanthan gum, guar gum, locust bean gum 등과 같은 교질물질을 첨가함으로써 효소의 안정성 외에 활성을 특이적으로 향상시킬 수 있는 새로운 방법 조사하였다. 정제된 PGase를 0.2%의 상술한 교질물질을 함유하는 동일한 완충용액에 잘 혼합시켜 30℃에서 배양하여 효소의 불활성화에 대한 일차반응 속도상수 k값을 구한 결과, 대조군의 k값이 0.0082 min<SUP>-1</SUP>인데 반해 xanthan gum 첨가 시는 0.0003 min<SUP>-1</SUP>, guar gum 첨가 시는 0.0001 min<SUP>-1</SUP>이하, locust bean gum 첨가 시는 0.0001 min<SUP>-1</SUP>로서 교질물질 첨가에 의해 효소의 안정성이 현저히 증가하였다. 또한 대조군에 비해 xanthan gum 첨가 시는 PGase의 상대활성이 89%가 증가되었으며, guar gum 첨가 시는 97%, locust bean gum 첨가 시는 90%가 증가되어 상술한 교질물질들이 효소의 활성 촉진제로서의 기능이 있음을 확인할 수 있었다. Guar gum 처리에 의해 약 2배의 활성이 증진된 상태로 당근 단세포 생성 반응을 수행한 결과 모든 반응시간에서 guar gum을 가했을 때가 PGase만을 가하여 단세포화 반응을 수행한 경우보다 높은 수율을 보였으며, 단세포화 반응 2시간 경과 후에 대조군 대비 13%의 가장 높은 수율 향상을 보였다. This study was carried out to enhance the stability and activity of polygalacturonase (PGase) purified from Kluyveromyces marxianus IFO 0288. Gums such as xanthan gum, guar gum, and locust bean gum were capable of increasing the catalytic stability and activity of the PGase. At 30℃, the rate constants for the inactivation of the PGase with xanthan gum, guar gum, and locust bean gum were estimated to be 0.0003 min<SUP>-1</SUP>, below 0.0001 min<SUP>-1</SUP>, and 0.0001 min<SUP>-1</SUP> respectively, whereas control was estimated to be 0.0082 min<SUP>-1</SUP>. The yield of the maceration reaction catalyzed by the PGase for the production of carrot single cells increased by 13% in the presence of guar gum, where the relative enzyme activity supplemented with guar gum was two-fold greater than that of the PGase alone.
FDTD Modeling for the Accurate Electromagnetic Wave Analysis of Graphene
Yeon‑Hwa Kim,Hongjin Choi,Jeahoon Cho,Kyung‑Young Jung 대한전기학회 2020 Journal of Electrical Engineering & Technology Vol.15 No.3
We develop a fnite-diference time-domain (FDTD) method suitable for the electromagnetic (EM) analysis of graphene. In this work, we employ the modifed Lorentz model for dispersion modeling, the two-dimensional (2-D) sheet model for geometrical modeling, and the complex-frequency-shifted (CFS)-perfectly matched layer (PML) for the absorbing boundary condition. In specifc, the accurate complex-conjugate pole-residue (CCPR) dispersion model is frst adapted for the electrical modeling of graphene by using the robust vector ftting. Next, the CCPR parameters are converted to the modifed Lorentz parameters and then the modifed Lorentz-based dispersive FDTD formulation is used to enhance the computational efciency. In FDTD cell modeling, the 2-D sheet cells are allocated for graphene rather than the conventional FDTD cell-based modeling. Finally, CFS-PML are employed for terminating the computational domain to avoid the late-time instability. The presented FDTD approach is validated in numerical examples for graphene-based parallel plate waveguides.