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Jinwoo Lee

Publications and source records attributed to Jinwoo Lee.

14 recordsLinked to original sources
PubMed2007

Crosslinked enzyme aggregates in hierarchically-ordered mesoporous silica: a simple and effective method for enzyme stabilization.

alpha-chymotrypsin (CT) and lipase (LP) were immobilized in hierarchically-ordered mesocellular mesoporous silica (HMMS) in a simple but effective way for the enzyme stabilization, which was achieved by the enzyme adsorption followed by glutaraldehyde (GA) crosslinking. This resulted in the formation of nanometer scale crosslinked enzyme aggregates (CLEAs) entrapped in the mesocellular pores of HMMS (37 nm), which did not leach out of HMMS through narrow mesoporous channels (13 nm). CLEA of alpha-chymotrypsin (CLEA-CT) in HMMS showed a high enzyme loading capacity and significantly increased enzyme stability. No activity decrease of CLEA-CT was observed for 2 weeks under even rigorously shaking condition, while adsorbed CT in HMMS and free CT showed a rapid inactivation due to the enzyme leaching and presumably autolysis, respectively. With the CLEA-CT in HMMS, however, there was no tryptic digestion observed suggesting that the CLEA-CT is not susceptible to autolysis. Moreover, CLEA of lipase (CLEA-LP) in HMMS retained 30% specific activity of free lipase with greatly enhanced stability. This work demonstrates that HMMS can be efficiently employed as host materials for enzyme immobilization leading to highly enhanced stability of the immobilized enzymes with high enzyme loading and activity.

Chymotrypsin↗
PubMed2005

Large-scale synthesis of TiO2 nanorods via nonhydrolytic sol-gel ester elimination reaction and their application to photocatalytic inactivation of E. coli.

A simple method of synthesizing a large quantity of TiO(2) nanorods was developed. A nonhydrolytic sol-gel reaction between titanium(IV) isopropoxide and oleic acid at 270 degrees C generated 3.4 nm (diameter) x 38 nm (length) sized TiO(2) nanocrystals. The transmission electron microscopic image showed that the particles have a uniform diameter distribution. X-ray diffraction and selected-area electron diffraction patterns combined with high-resolution transmission electron microscopic image showed that the TiO(2) nanorods are highly crystalline anatase crystal structure grown along the [001] direction. The diameters of the TiO(2) nanorods were controlled by adding 1-hexadecylamine to the reaction mixture as a cosurfactant. TiO(2) nanorods with average sizes of 2.7 nm x 28 nm, 2.2 nm x 32 nm, and 2.0 nm x 39 nm were obtained using 1, 5, and 10 mmol of 1-hexadecylamine, respectively. The optical absorption spectrum of the TiO(2) nanorods exhibited that the band gap of the nanorods was 3.33 eV at room temperature, which is 130 meV larger than that of bulk anatase (3.2 eV), demonstrating the quantum confinement effect. Oleic acid coordinated on the nanorod surface was removed by the reduction of the carboxyl group of oleic acid, and the Brunauer-Emmett-Teller surface area of the resulting naked TiO(2) nanorods was 198 m(2)/g. The naked TiO(2) nanorods exhibited higher photocatalytic activity than the P-25 photocatalyst for the photocatalytic inactivation of E. coli.

Catalysis↗
PubMed2005

Simple synthesis of hierarchically ordered mesocellular mesoporous silica materials hosting crosslinked enzyme aggregates.

Hierarchically ordered mesocellular mesoporous silica materials (HMMS) were synthesized using a single structure-directing agent. The mesocellular pores are synthesized without adding any pore expander; the pore walls are composed of SBA-15 type mesopores. Small-angle X-ray scattering revealed the presence of uniform pore structures with two different sizes. Using HMMS as a nanoscopic template, hierarchically ordered mesocellular mesoporous carbon (HMMC) and polymer (HMMP) materials were synthesized. HMMS was used as a host for enzyme immobilization. To improve the retention of enzymes in HMMS, we adsorbed enzymes, and then employed crosslinking using glutaraldehyde (GA). The resulting crosslinked enzyme aggregates (CLEAs) show an impressive stability with extremely high enzyme loadings. For example, 0.5 g alpha-chymotrypsin (CT) could be loaded in 1 g of silica with no activity decrease observed with rigorous shaking over one month. In contrast, adsorbed CT without GA treatment resulted in a lower loading, which further decreased due to continuous leaching of adsorbed CT under shaking. The activity of crosslinked CT aggregates in HMMS was approximately 10 times higher than that of the adsorbed CT, which represents a 74-fold increase in activity per unit weight of HMMS due to higher CT loading.

Adsorption↗
PubMed2005

Effects of Yukmijihwang-tang derivatives (YMJd), a memory enhancing herbal extract, on the gene-expression profile in the rat hippocampus.

The herbal extract Yukmijihwang-tang (YMJ) has been widely used for centuries as an anti-aging herbal medicine in Asian countries. Among the various modified prescriptions of YMJ, YMJ derivatives (YMJd) were formulated to enhance memory retention. This study has three goals: 1) to quantitatively evaluate the memory-enhancing effect of YMJd using behavior tasks; 2) to use cDNA micro-array tools to identify candidate genes responsible for enhancing memory; and 3) to statistically evaluate the specific gene expression patterns using Real-time PCR. Memory retention abilities are addressed by the passive avoidance task with SD male rat. The retention time of the YMJd group was significantly delayed (ca. 100%), whereas with Ginkgo biloba and Soya lecithin treatment, this was only delayed 20% and 10%, respectively. The cDNA from the hippocampi of YMJd and rat control groups were applied to an Incyte rat GEM2 cDNA microarray. The microarray results showed that transthyretin and PEP-19 were abundantly expressed in the YMJd treated group. Importantly, PEP-19 is a neuron-specific protein that inhibits apoptotic processes. On the other hand, neuronal genes involved in neuronal death or neurodegeneration, such as pentraxin and spectrin, were abundantly expressed in the control group. The list of differentially expressed genes may provide further insight into the action and mechanism behind the memory-enhancing effect of herbal extracts of YMJd.

Animals↗
PubMed2004

Ginsenoside Rg1 enhances CD4(+) T-cell activities and modulates Th1/Th2 differentiation.

Panax ginseng is commonly used as a tonic medicine in Asian countries such as Korea, China, and Japan. It has been reported that ginsenoside Rg1 in P. ginseng increases the proportion of T helper (Th) cells among the total number of T cells and promotes IL-2 gene expression in murine splenocytes. This implies that ginsenoside Rg1 increases the immune activity of CD4(+) T cells, however, the exact mechanism remains unknown. The present study elucidated the direct effect of Rg1 on helper T-cell activities and on Th1/Th2 lineage development. The results demonstrated that ginsenoside Rg1 had no mitogenic effects on unstimulated CD4(+) T cells, but augmented CD4(+) T-cell proliferation upon activation with anti-CD3/anti-CD28 antibodies in a dose-dependent manner. Rg1 also enhanced the expression of cell surface protein CD69 on CD4(+) T cells. In Th0 condition, ginsenoside Rg1 increases the expression of IL-2 mRNA, and enhances the expression of IL-4 mRNA on CD4(+) T cells, suggesting that Rg1 prefers to induce Th2 lineage development. In addition, ginsenoside Rg1 increases IL-4 secretion in CD4(+) T cells under Th2 skewed condition, while decreasing IFN-gamma secretion of cells in Th1 polarizing condition. Thus, Rg1 enhances Th2 lineage development from the naïve CD4(+) T cell both by increasing Th2 specific cytokine secretion and by repressing Th1 specific cytokine production. Therefore, these results suggest that ginsenoside Rg1 is a desirable agent for enhancing CD4(+) T-cell activity, as well as the correction of Th1-dominant pathological disorders.

Animals↗
PubMed2004

Nelumbinis Semen reverses a decrease in 5-HT1A receptor binding induced by chronic mild stress, a depression-like symptom.

Depression is associated with a dysfunctional serotonin (5-hydroxytryptamine; 5-HT) system. More recently, several lines of evidence suggest that an important factor in the development of depression may be a deficit in the function and expression of 5-HT1A receptors. The present study assessed if Nelumbinis Semen (N.s.) had an anti-depression effect through reversing a decrease in 5-HT1A receptor binding in rats with depression-like symptoms induced by chronic mild stress. Using a 5-HT1A receptor binding assay, with a specific 5-HT1A receptor agonist, 8-OH-DPAT (8-hydroxy-2-(di-n-propylamino) tetralin), the mechanism of the anti-depression effect of N.s. on rats was investigated, and the effects compared with two well-known antidepressants, Hyperium Perforatum (St. Johns Wort) and fluoxetine (Prozac). Animals were divided into five groups: the normal (N) group without chronic mild stress (CMS), the control (C) group under CMS for 8 weeks, the Nelumbinis Semen (N.s.) treatment group under CMS for 8 weeks, the Hyperium Perforatum (H.p.) treatment group under CMS for 8 weeks and finally, the fluoxetine (F) treatment group under CMS for 8 weeks. Each treatment was administered to rats during the last 4 weeks of the 8-week CMS. A sucrose intake test was performed to test the anti-depression effect of N.s. The N.s. treatment significantly reversed the decreased sucrose intake under CMS (P < 0.05 compared to control group under CMS). In the CA2 and CA3 regions of the hippocampus, both N.s. and H.p. reversed the CMS-induced decrease in 5-HT1A receptor binding. In the I to II regions of the frontal cortex, N.s. and H.p. also reversed the CMS-induced decrease in 5-HT1A receptor binding, and even showed a significant increase in 5-HT1A receptor binding compared to the F treatment group (N.s. vs. P, p < 0.05, H.p. vs. P, p < 0.05). However, in the hypothalamus, all treatments reversed the CMS-induced decrease in 5-HT1A receptor binding. This reversal effect of N.s. on the decrease in 5-HT1A receptor binding in the frontal cortex, hippocampus and hypothalamus of rat brains was very similar to that of H.p, but different from that of F. It is concluded that N.s. presents an anti-depression effect through enhancing 5-HT1A receptor binding.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed2003

A facile synthesis of bimodal mesoporous silica and its replication for bimodal mesoporous carbon.

Bimodal mesoporous silica material composed of 30-40 nm sized nanoparticles with 3.5 nm sized three-dimensionally interconnected mesopores was synthesized under neutral conditions using sodium silicate as a silica source. Using the bimodal mesoporous silica as a template, bimodal mesoporous carbon having 4 nm sized framework mesopores and approximately 30 nm sized textural pores was synthesized.

Journal Article↗