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288
result(s) for
"Lee, Sung-Gyu"
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Observation of an exceptional point in a non-Hermitian metasurface
by
Baek, Soojeong
,
Ha, Taewoo
,
Zhang, Shuang
in
asymmetric polarization conversion
,
Broken symmetry
,
Circular polarization
2020
Exceptional points (EPs), also known as non-Hermitian degeneracies, have been observed in parity-time symmetric metasurfaces as parity-time symmetry breaking points. However, the parity-time symmetry condition puts constraints on the metasurface parameter space, excluding the full examination of unique properties that stem from an EP. Here, we thus design a general non-Hermitian metasurface with a unit cell containing two orthogonally oriented split-ring resonators (SRRs) with overlapping resonance but different scattering rates and radiation efficiencies. Such a design grants us full access to the parameter space around the EP. The parameter space around the EP is first examined by varying the incident radiation frequency and coupling between SRRs. We further demonstrate that the EP is also observable by varying the incident radiation frequency along with the incident angle. Through both methods, we validate the existence of an EP by observing unique level crossing behavior, eigenstate swapping under encirclement, and asymmetric transmission of circularly polarized light.
Journal Article
Synergistic Protective Effects of Haematococcus pluvialis -Derived Astaxanthin and Walnut Shell Polyphenols Against Particulate Matter (PM) 2.5 -Induced Pulmonary Inflammation
2025
Airborne particulate matter (PM) triggers oxidative stress and inflammation in pulmonary tissues, contributing to chronic respiratory diseases. This study evaluated the antioxidant and anti-inflammatory effects of a combined extract of
(
and walnut shell (HW extract) and its protective efficacy against PM
-induced pulmonary inflammation. Extracts mixed at different ratios (10:0-0:10,
/
) were tested using 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging, cell-based assays, HPLC quantification, molecular docking, and a PM
-induced pulmonary inflammation mouse model. The optimized 6:4 mixture showed the strongest antioxidant activity (RC
= 0.61 ± 0.14 μg/mL) and significantly reduced nitric oxide (NO) and cyclooxygenase-2 (COX-2) expression without cytotoxicity. HPLC confirmed the presence of astaxanthin (1.714 μg/mg) and quercetin (0.722 μg/mg). Docking simulations indicated strong COX-2 binding affinities (-9.501 and -8.753 kcal/mol) through hydrogen bonding and hydrophobic interactions. In vivo, HW extract reduced leukocyte infiltration, serum IL-6 levels, and pulmonary expression of COX-2, interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α) while improving alveolar structure. These results suggest that HW extract exerts synergistic antioxidant and anti-inflammatory actions via dual-site COX-2 modulation, providing a promising natural therapeutic approach for mitigating PM
-induced respiratory inflammation.
Journal Article
Antioxidative and Anti-Atopic Dermatitis Effects of Peptides Derived from Hydrolyzed Sebastes schlegelii Tail By-Products
by
Lee, Sung-Gyu
,
Kang, Hyun
,
Hwang, Jin-Woo
in
Amino acids
,
Animals
,
Anti-Inflammatory Agents - chemistry
2024
Atopic dermatitis (AD) is a chronic inflammatory skin disorder associated with significant morbidity, including pruritus, recurrent skin lesions, and immune dysregulation. This study aimed to investigate the antioxidative and anti-AD effects of peptides derived from hydrolyzed Sebastes schlegelii (Korea rockfish) tail by-products. Hydrolysates were prepared using various enzymes, including Alcalase, Flavourzyme, Neutrase, and Protamex. Among them, Protamex hydrolysates demonstrated the highest ABTS radical scavenging activity with an RC50 value of 69.69 ± 0.41 µg/mL. Peptides were further isolated from the Protamex hydrolysate using dialysis, fast protein liquid chromatography (FPLC), and high-performance liquid chromatography (HPLC). The most active peptide, STPO-B-II, exhibited a single peak and was identified as a sequence of Glu-Leu-Ala-Lys-Thr-Trp-His-Asp-Met-Lys, designated as MP003. In vivo experiments were conducted using a 2,4-dinitrochlorbenzene (DNCB)-induced AD model in NC/Nga mice. The isolated peptide, MP003, showed significantly reduced AD symptoms, including erythema, lichenification, and collagen deposition. Additionally, MP003 decreased epidermal and dermal thickness, eosinophil, and mast cell infiltration and downregulated the expression of pro-inflammatory cytokines IL-1β, IL-6, and IgE in serum and skin tissues. These findings suggest that peptides derived from Sebastes schlegelii tail by-products may serve as potential therapeutic agents for AD.
Journal Article
Regional Variation in Antioxidant and Anti-Inflammatory Activities of the Brown Alga Sargassum thunbergii and Mechanistic Role of Fucosterol in Inflammation Modulation
2025
Background/Objectives: Natural products derived from marine algae serve as promising reservoirs of bioactive compounds for preventing and managing inflammation-associated diseases. This study systematically investigated the regional variations in antioxidant and anti-inflammatory activities of the brown alga Sargassum thunbergii collected from seven coastal regions of Korea and elucidated the underlying mechanisms of action. Methods: Among all samples, the extract from Haeundae-gu exhibited the highest total polyphenol (47.3 ± 2.1 mg GAE/g) and flavonoid (19.8 ± 1.7 mg QE/g) contents, showing superior antioxidant activity in 2,2-diphenyl-1-picrylhydrazyl (DPPH) (RC50 = 44.54 µg/mL), 2,2′-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) (RC50 = 36.42 µg/mL), and ferric reducing antioxidant power (FRAP) (0.56 mM FeSO4 eq/mg) assays. In lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages, the Haeundae-gu extract markedly suppressed nitric oxide (NO) production and downregulated inducible nitric oxide synthase (iNOS) expression in a dose-dependent manner without cytotoxic effects. High-performance liquid chromatography (HPLC) identified fucosterol (10.23 ± 0.17 mg/g extract) as a predominant sterol component, and molecular docking analysis revealed specific hydrogen bonding of fucosterol with TYR489 in the active site of iNOS (GlideScore = −4.774 kcal/mol). Results: These findings indicate that both phenolic compounds and sterols such as fucosterol act synergistically to enhance the antioxidant and anti-inflammatory effects of S. thunbergii. Conclusions: In summary, the mechanistic and functional insights obtained in this study highlight S. thunbergii, particularly from Haeundae-gu, as a promising marine-derived bioresource for developing nutraceuticals and therapeutic interventions against oxidative stress and inflammation-related disorders.
Journal Article
Antioxidant and Skin-Whitening Efficacy of a Novel Decapeptide (DP, KGYSSYICDK) Derived from Fish By-Products
2024
The skin is vulnerable to damage from ultraviolet rays and oxidative stress, which can lead to aging and pigmentation issues. This study investigates the antioxidant and whitening efficacy of a decapeptide (DP, KGYSSYICDK) derived from marine fish by-products and evaluates its potential as a new skin-whitening agent. DP demonstrated high antioxidant activity, showing comparable or superior performance to Vitamin C (Vit. C) in ferric reducing antioxidant power (FRAP) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging assays. In hydrogen peroxide (H2O2)-treated HaCaT cells, DP increased cell viability and reduced reactive oxygen species (ROS) generation. Furthermore, DP inhibited tyrosinase activity and decreased melanin production in α-melanocyte stimulating hormone (α-MSH)-induced B16F10 melanoma cells in a dose-dependent manner. Reverse transcription polymerase chain reaction (RT-PCR) analysis revealed that DP reduces the mRNA expression of MITF, tyrosinase, and MC1R, thus suppressing melanin production. DP exhibits strong binding interactions with multiple amino acid residues of tyrosinase, indicating potent inhibitory effects on the enzyme. These results suggest that DP possesses significant antioxidant and whitening properties, highlighting its potential as a skin-whitening agent. Future research should focus on optimizing DP’s structure and exploring structure–activity relationships.
Journal Article
Antioxidant, Antibacterial Properties of Novel Peptide CP by Enzymatic Hydrolysis of Chromis notata By-Products and Its Efficacy on Atopic Dermatitis
by
Lee, Sung-Gyu
,
Kang, Hyun
,
Hwang, Jin-Woo
in
Amino acid sequence
,
Amino acid sequences
,
Amino acids
2024
This study investigated the antioxidant, antimicrobial, and anti-atopic dermatitis (AD) effects of a novel peptide (CP) derived from a Chromis notata by-product hydrolysate. Alcalase, Flavourzyme, Neutrase, and Protamex enzymes were used to hydrolyze the C. notata by-product protein, and the 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical-scavenging activity was measured. Alcalase hydrolysate exhibited the highest ABTS radical-scavenging activity, leading to the selection of Alcalase for further purification. The CHAO-1-I fraction, with the highest ABTS activity, was isolated and further purified, resulting in the identification of the peptide CP with the amino acid sequence Ala-Gln-Val-Met-Lys-Leu-Pro-His-Arg-Met-Gln-His-Ser-Gln-Ser. CP demonstrated antimicrobial activity against Staphylococcus aureus, inhibiting its growth. In a 2,4-dinitrochlorobenzene (DNCB)-induced AD-like skin model in mice, CP significantly alleviated skin lesions, reduced epidermal and dermal thickness, and inhibited mast cell infiltration. Moreover, CP suppressed the elevated levels of interleukin-6 (IL-6) in the plasma of DNCB-induced mice. These findings highlight the potential of CP as a therapeutic agent for AD and suggest a novel application of this C. notata by-product in the fish processing industry.
Journal Article
Effect of E. cava and C. indicum Complex Extract on Phorbol 12-Myristate 13-Acetate (PMA)-Stimulated Inflammatory Response in Human Pulmonary Epithelial Cells and Particulate Matter (PM)2.5-Induced Pulmonary Inflammation in Mice
2023
This study explores the potential of a natural composite formulation known as ED, consisting of Ecklonia cava (E. cava, family: Lessoniaceae) and Chrysanthemum indicum Linne (C. indicum, family: Asteraceae), in alleviating lung inflammation induced by fine particulate matter (PM2.5). Initial assessments confirmed that neither ED nor one of its components, dieckol, exhibited cytotoxic effects on A549 cells. Subsequently, the impact of ED and dieckol on MUC5AC gene expression in A549 cells stimulated by phorbol 12-myristate 13-acetate (PMA) was investigated, revealing promising results that demonstrated a dose-dependent inhibition of MUC5AC gene expression. The study also delves into the underlying mechanisms, demonstrating that ED and dieckol effectively suppressed the phosphorylation of mitogen-activated protein kinases (MAPKs), including JNK, ERK, and p38, which are known to be involved in the regulation of MUC5AC gene expression. In in vivo experiments using a PM2.5-induced pulmonary inflammation mouse model, the research findings showed that ED mitigated cellular accumulation in the airways, leading to a significant reduction in the total cell count in bronchoalveolar lavage fluid (BALF). Moreover, ED exhibited protective effects against PM2.5-induced pulmonary damage, characterized by reduced inflammatory cell infiltration and decreased mucus secretion in pulmonary tissues. Additionally, ED’s anti-inflammatory properties were evident in its ability to decrease the levels of key inflammatory cytokines, TNF-α and IL-6, both in the serum and lung tissue of the PM2.5-induced pulmonary inflammation mouse model. These findings suggest the potential of ED as a therapeutic agent for inflammatory respiratory diseases.
Journal Article
Characterizing nanoscale spatiotemporal defects of multi-layered MoSe2 in hyper-temporal transient nanoscopy
2025
We directly characterize nanoscale spatiotemporal inhomogeneities of multi-layered molybdenum diselenide (MoSe
) in real space and time – the nanometre–femtosecond scale, attributing to local mechanical structures such as strain and surface/subsurface defects, which are critical in semiconductor and optoelectronic applications. This remarkable precision is achieved through the development of a hyper-temporal transient nanoscopy incorporating a sideband-coupled generalized lock-in amplification technique, allowing for characterization of local spatiotemporal defects at each pixel within a subwavelength mapping region. By utilizing this technique, we characterize the nanoscale strain-induced spatiotemporal defects of multi-layered MoSe
, including nano-bubbles that exhibit a noticeable reduction in exciton-exciton annihilation rates, which may attribute to the suppressed probability of bimolecular interaction of excitons due to the strain-induced band distortion. Moreover, we visualize topographically hidden spatiotemporal defects such as lattice mismatches, which induce mid-gap states that traps charge carriers and thereby slow down recombination process. We propose that this hyper-temporal approach to resolving intricate spatiotemporal inhomogeneities in van der Waals materials provides significant insights into their optoelectronic properties and opens new avenues for innovative material design and characterization.
Journal Article
ED Formula, a Complex of Ecklonia cava and Chrysanthemum indicum, Ameliorates Airway Inflammation in Lipopolysaccharide-Stimulated RAW Macrophages and Ovalbumin-Induced Asthma Mouse Model
by
Kwon, Sang-Oh
,
Park, Chan-Hwi
,
Lee, Sung-Gyu
in
airway inflammation
,
Asthma
,
Chrysanthemum indicum
2023
Ecklonia cava (E. cava) and Chrysanthemum indicum Linne (C. indicum) are natural raw materials known to have beneficial effects on inflammatory-related diseases, as evidenced by various sources in the literature. This study aimed to investigate the airway-protective effects of a formulation called ED, comprising E. cava and C. indicum, by evaluating its potential anti-inflammatory properties. Methods: The major components of ED were analyzed using high-performance liquid chromatography (HPLC) and its anti-inflammatory activity was assessed in RAW 264.7 cells through measurements of nitric oxide’s (NO) inhibitory effect, cyclooxygenase (COX)-2 protein expression, and the mitogen-activated protein kinase (MAPK) signaling pathway. Additionally, the anti-inflammatory effect of ED was evaluated in an ovalbumin-induced asthma model by measuring cytokine levels in serum, bronchoalveolar lavage fluid (BALF), and lung tissue. Through HPLC analysis, the major components of ED, dieckol and luteolin, were identified. ED demonstrated no cytotoxicity and effectively reduced NO production in lipopolysaccharide (LPS)-induced RAW 264.7 cells. Moreover, ED downregulated COX-2 expression through the MAPK signaling pathway in LPS-induced RAW 264.7 cells. In the ovalbumin-induced asthma model, the ED-treated group exhibited reduced levels of inflammatory cytokines in lung tissue. Furthermore, the ED-treated group showed a decrease in the number of inflammatory cells in BALF and lower serum interleukin (IL)-6 levels compared to the ovalbumin-treated group. These results suggest that ED has the potential to be a novel therapeutic agent for improving inflammatory respiratory diseases.
Journal Article
Characteristics and Prognosis of Colorectal Cancer after Liver or Kidney Transplantation
2021
Background
The purpose of this study was to evaluate the characteristics and prognosis of de novo CRC patients who underwent liver or kidney transplantation.
Methods
We retrospectively reviewed the medical records of 66 de novo CRC patients selected from 8,734 liver transplant (LT) or kidney transplant (KT) recipients. We analyzed characteristics and survival outcomes of de novo CRC patients and sporadic CRC patients who underwent radical surgery with stage I-III in Asan Medical Center between 2005 and 2016. Survival outcomes were analyzed via the 1:4 matching method.
Results
The standard incidence ratio (SIR) of de novo CRC in KT recipients is 1.67 in men and 2.54 in women. That in LT recipients is 3.10 in men and 2.25 in women. Compared with sporadic CRC patients, de novo CRC patients had more colon cancer than rectal cancer (
p
=0.041). In 9 patients (13.6%), CRC was diagnosed within one year after transplantation, 21 patients (31.8%) were diagnosed between 1–5 years, and the remaining 36 patients (54.6%) were diagnosed thereafter. There were no significant differences in recurrence-free survival and overall survival between the two groups (
p
=0.211 and
p
=0.324, respectively).
Conclusions
The risk of developing de novo CRC in transplant recipients was higher than in the general population. The survival outcome of de novo CRC was no different compared with the sporadic CRC. Therefore, regular surveillance is essential for timely diagnosis and treatment for transplantation patients. A large prospective study for an intense CRC surveillance program in transplantation patients is needed.
Journal Article