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Physiological and biochemical responses of Ulva pertusa to metal exposure
Geonhee Kim(김건희),Jihae Park(박지혜),Soyeon Choi(최소연),Hojun Lee(이호준),Taejun Han(한태준) 환경독성보건학회 2021 한국독성학회 심포지움 및 학술발표회 Vol.2021 No.5
The green alga Ulva is considered to be a simple, homogeneous algal form with little functional differentiation within the thallus. Functional differentiation of the thallus is a strategy that contributes to the survival of Ulva pertusa as an opportunistic alga. Although many ecotoxicity assessments have been conducted based on spore-forming properties of the marginal thallus parts, ecotoxicity using the middle parts of the thallus has rarely been achieved. Therefore, we investigated the response of the middle and marginal thallus region of Ulva pertusa to exposure of six heavy metals (Cu, Cr, Cd, Ni, As, Ag). Concentration-dependent reduction in disc size, Fv/Fm, ETRmax and pigment were observed with Ag being the most toxic to Ulva pertusa.
Haeun CHO,Geonhee HAN,Kwang Yeon HWANG,Sun Hwa KIM,Yooso YANG 한국생물공학회 2021 한국생물공학회 학술대회 Vol.2021 No.10
Exosomes are a type of extracellular vesicles with a diameter of 30 to 150 ㎚, and are secreted by multiple cell types. Exosomes can mediate cell-to-cell communication and modulate many physiological and pathological processes by carrying biomolecules such as nucleic acids, proteins and metabolites. In particular, bovine milk is a readily accessible source for mass production of exosome, and milk-exosomes can effectively deliver inflammatory and immunomodulatory active cargo through the gastrointestinal tract in a stable form. Here, we investigated the beneficial effects of bovine milk, especially colostrum-derived exosomes in a murine model of ulcerative colitis induced by dextran sodium sulfate (DSS). Our results showed that oral gavage of colostrum-derived exosomes can alleviate colitis symptoms such as abdominal pain, loss weight, diarrhea and rectal bleeding by regulating intestinal inflammatory immune responses. Collectively, our findings that bovine colostrum-derived exosomes with excellent structural and functional stability offer great potential as natural therapeutics for the recovery of colitis, may broaden the applications of milk consumption.
Prebiotic effect of resistant maltodextrin analyzed by in vitro digestion, and fecal fermentation
Seong Won Cheon,Geonhee Kim,Dong Hyeon Lee,Minsu Kim,Kyoung-Hee Cho,Nam Soo Han 한국식품영양과학회 2021 한국식품영양과학회 학술대회발표집 Vol.2021 No.10
The importance of dietary fiber has been highlighted, which has led to increased interest in functional fiber ingredients such as resistant maltodextrin (RMD). However, the evaluation of prebiotic effects by RMDs is limited. The aim of this study was to evaluate the prebiotic effects of five RMDs, by analyzing changes in the gut microbiome and metabolites. For this, in vitro digestion and fecal fermentation on RMDs were performed. As a result, the single culture studies showed that among 21 species, only B. xylanisolvens utilized those RMDs most efficiently, but which the others poorly used. The digestibility of RMDs in in vitro digestion was highest in TDF75, followed by Fibersol-2, Nutriose in the order. In in vitro fecal fermentation using RMDs as carbon sources, NGS analysis showed that Bacteroides spp. increased in the genus level. In addition, metabolite analysis showed that SCFAs, such as acetate and propionate increased, conversion of betaine to TMA was inhibited, and vitamin B7 increased. In conclusion, RMDs appeared that it may contribute to gut health with limited prebiotic effects by promoting the growth of Bacteroides spp., which are considered potential probiotics.
Fully Dispersed Rh Ensemble Catalyst To Enhance Low-Temperature Activity
Jeong, Hojin,Lee, Geonhee,Kim, Beom-Sik,Bae, Junemin,Han, Jeong Woo,Lee, Hyunjoo American Chemical Society 2018 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.140 No.30
<P>Minimizing the use of precious metal catalysts is important in many applications. Single-atom catalysts (SACs) have received much attention because all of the metal atoms can be used for surface reactions. However, SACs cannot catalyze some important reactions that require ensemble sites. Here, Rh catalysts were prepared by treating 2 wt % Rh/CeO<SUB>2</SUB> hydrothermally at 750 °C for 25 h. Nearly 100% dispersion was obtained, but the surface Rh atoms were not isolated (denoted as ENS). They catalyzed the oxidation of C<SUB>3</SUB>H<SUB>6</SUB> or C<SUB>3</SUB>H<SUB>8</SUB> at low temperatures, but these oxidations did not occur on the Rh SAC. When the simultaneous oxidation of CO, C<SUB>3</SUB>H<SUB>6</SUB>, and C<SUB>3</SUB>H<SUB>8</SUB> was performed, the <I>T</I><SUB>20</SUB> (temperature at conversion 20%) for CO oxidation increased significantly from 40 °C for sole CO oxidation to 180 °C on SAC due to the competitive adsorption of hydrocarbons. However, <I>T</I><SUB>20</SUB> increased much less on ENS, from 60 to 100 °C. ENS exhibited superior activity for low-temperature oxidation. During hydrothermal treatment for 25 h, the Rh size initially increased from 2.3 to 6.7 nm then decreased to 0.9 nm. The surface hydroxyl groups formed on the catalyst surface help detach Rh atoms from Rh clusters, while preventing the reaggregation of dispersed Rh atoms into Rh clusters. This fully dispersed catalyst would have maximum atom-efficiency while catalyzing various surface reactions.</P> [FIG OMISSION]</BR>
Lee, Dennis T.,Chung, Jong Won,Park, Geonhee,Kim, Yun-Tae,Lee, Chang Young,Cho, Yeonchoo,Yoo, Pil J.,Han, Jae-Hee,Shin, Hyeon-Jin,Kim, Woo-Jae Elsevier 2018 APPLIED SURFACE SCIENCE - Vol.429 No.-
<P><B>Abstract</B></P> <P>Semiconducting single-walled carbon nanotubes (SWNTs) show promise as core materials for next-generation solar cells and nanoelectronic devices. However, most commercial SWNT production methods generate mixtures of metallic SWNTs (m-SWNTs) and semiconducting SWNT (sc-SWNTs). Therefore, sc-SWNTs must be separated from their original mixtures before use. In this study, we investigated a polymer-based, noncovalent sc-SWNT separation approach, which is simple to perform and does not disrupt the electrical properties of the SWNTs, thus improving the performance of the corresponding sc-SWNT-based applications. By systematically investigating the effect that different structural features of the semiconductor polymer have on the separation of sc-SWNTs, we discovered that the length and configuration of the alkyl side chains and the rigidity of the backbone structure exert significant effects on the efficiency of sc-SWNT separation. We also found that electron transfer between the semiconductor polymers and sc-SWNTs is strongly affected by their energy-level alignment, which can be tailored by controlling the donor-acceptor configuration in the polymer backbone structures. Among the polymers investigated, the highly planar P8T2Z-C12 semiconductor polymer showed the best sc-SWNT separation efficiency and unprecedentedly strong electronic interaction with the sc-SWNTs, which is important for improving their performance in applications.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The effect of polymers’ structural features on the separation of sc-SWNTs is explored. </LI> <LI> Polymer’s alkyl side-chain length and orientation are keys in sc-SWNT separation. </LI> <LI> The rigidity of the backbone structure is key factor in efficient separation of sc-SWNTs. </LI> <LI> Energy level alignment of polymer and sc-SWNTs is important for device performance. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Song, Inhak,Lee, Jaeha,Lee, Geonhee,Han, Jeong Woo,Kim, Do Heui American Chemical Society 2018 The Journal of Physical Chemistry Part C Vol.122 No.29
<P>V/TiO<SUB>2</SUB> catalysts are used in various reactions, including oxidative dehydrogenation, partial oxidation of ethanol, and selective catalytic reduction of NO<SUB><I>x</I></SUB> with NH<SUB>3</SUB>. In this work, we investigated the effect of supported monomeric vanadium oxide (VO<SUB>3</SUB>) on the acidity of anatase TiO<SUB>2</SUB>(101) surface by using density functional theory calculations combined with in situ diffuse reflectance infrared Fourier transform (DRIFT) experiments. The hydrogenation of TiO<SUB>2</SUB> to form hydroxyl groups on the surface was energetically more favorable in the presence of the supported monomeric vanadium oxide. Charge transfer between TiO<SUB>2</SUB> support and VO<SUB>3</SUB> was considered as an origin of −OH stabilization, which made Brønsted acid sites more abundant on the V/TiO<SUB>2</SUB> surface than on TiO<SUB>2</SUB>. Moreover, it was observed that the cationic vanadium center in VO<SUB>3</SUB> can act as much weaker Lewis acid sites than the titanium center in TiO<SUB>2</SUB>. Such weakened acidity of Lewis acid sites in the presence of monomeric vanadium oxide was consistently observed in in situ DRIFT results, which could explain the higher reactivity of NH<SUB>3</SUB> adsorbed on Lewis acid sites of V/TiO<SUB>2</SUB> than those of TiO<SUB>2</SUB> in the NH<SUB>3</SUB>-selective catalytic reduction reaction.</P> [FIG OMISSION]</BR>
Ulva bioassay as a tool to assess potential toxicity in industrial wastewater
Hojun Lee(이호준),Kisik Shin(신기식),Jihae Park(박지혜),Soyeon Choi(최소연),Geonhee Kim(김건희),Stephen Depuydt(스테픈 데퓨잇),Taejun Han(한태준) 환경독성보건학회 2021 한국독성학회 심포지움 및 학술발표회 Vol.2021 No.5
Industrial wastewater is a complex source of organic and man-made pollutants containing numerous metal ions. These effluents can be a major problem for the environment due to their complex chemical content, which is known for its toxicity and low biodegradability, which can have harmful effects on the aquatic environment. In this study, we used the green macroalga Ulva pertusa to evaluate the toxicity of wastewater samples from 99 industries in South Korea and to characterize the relationship between ecotoxicity and chemical content to identify chemicals that could contribute to overall ecotoxicity. Although the metal content of most of the effluents did not exceed the allowable criteria, the measured ecological toxicity of the effluents is related to Cd, Cu, Ni, Pb and Zn. Specifically in the area of metals, the Ulva bioassay shows a positive and important relationship with Cr. These results highlight the importance of biological assays to continuously monitor the toxicity of treated wastewater to prevent harmful effects on the environment. The results also suggest that ecotoxicity data are needed in parallel with chemical data to better assess the safety of wastewater discharges to the environment.