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91.
Young Mi Ha Yohei Uehara Daeui Park Hyoung Oh Jeong Ji Young Park Yun Jung Park Ji Yeon Lee Hye Jin Lee Yu Min Song Hyung Ryong Moon Hae Young Chung 《Applied biochemistry and biotechnology》2012,168(6):1416-1433
We describe the design, synthesis, and biological activities of 5-chloro-2-(substituted phenyl)benzo[d]thiazole derivatives as novel tyrosinase inhibitors. Among them, 4-(5-chloro-2,3-dihydrobenzo[d]thiazol-2-yl)-2,6-dimethoxyphenol (MHY884) and 2-bromo-4-(5-chloro-benzo[d]thiazol-2-yl)phenol (MHY966) showed inhibitory activity higher than or similar to kojic acid, against mushroom tyrosinase. Therefore, we carried out kinetic studies on the two compounds with potent tyrosinase inhibitory effects. Kinetic analysis of tyrosinase inhibition revealed that all of these compounds are competitive inhibitors. MHY884 and MHY966 effectively inhibited tyrosinase activity and reduced melanin levels in B16 cells treated with ??-melanocyte stimulating hormone (??-MSH). These data strongly suggest that the newly synthesized compounds MHY884 and MHY966 could suppress production of melanin via inhibition of tyrosinase activity. 相似文献
92.
A lithium ion conducting glass, Li2O-B2O3-SiO2, is fabricated by the conventional melt and quenching technique from a mixture of Li2CO3, B2O3 and SiO2 powders. It appears that B2O3 decreases the crystallization tendency of the Li2O-SiO2 binary glass, resulting in an expanded glass forming region in the Li2O-B2O3-SiO2 ternary glass. The maximum conductivity is 2 × 10− 6 S cm− 1 at 25 °C for the 50Li2O-38B2O3-12SiO2 glass sample. The observed high conductivity is due to the mixed former effect. The conductivity strongly depends on the Li2O content, but not on K (SiO2/B2O3) in the Li2O-B2O3-SiO2 ternary glass. 相似文献
93.
Rolczynski BS Szarko JM Son HJ Liang Y Yu L Chen LX 《Journal of the American Chemical Society》2012,134(9):4142-4152
Record-setting organic photovoltaic cells with PTB polymers have recently achieved ~8% power conversion efficiencies (PCE). A subset of these polymers, the PTBF series, has a common conjugated backbone with alternating thieno[3,4-b]thiophene and benzodithiophene moieties but differs by the number and position of pendant fluorine atoms attached to the backbone. These electron-withdrawing pendant fluorine atoms fine tune the energetics of the polymers and result in device PCE variations of 2-8%. Using near-IR, ultrafast optical transient absorption (TA) spectroscopy combined with steady-state electrochemical methods we were able to obtain TA signatures not only for the exciton and charge-separated states but also for an intramolecular ("pseudo") charge-transfer state in isolated PTBF polymers in solution, in the absence of the acceptor phenyl-C(61)-butyric acid methyl ester (PCBM) molecules. This led to the discovery of branched pathways for intramolecular, ultrafast exciton splitting to populate (a) the charge-separated states or (b) the intramolecular charge-transfer states on the subpicosecond time scale. Depending on the number and position of the fluorine pendant atoms, the charge-separation/transfer kinetics and their branching ratios vary according to the trend for the electron density distribution in favor of the local charge-separation direction. More importantly, a linear correlation is found between the branching ratio of intramolecular charge transfer and the charge separation of hole-electron pairs in isolated polymers versus the device fill factor and PCE. The origin of this correlation and its implications in materials design and device performance are discussed. 相似文献
94.
Sae‐Jin Kim Joohwi Lee Seung‐Cheol Lee Chan Park Cheol Seong Hwang Jung‐Hae Choi 《固体物理学:研究快报》2012,6(3):108-110
The migration barrier energies of the nitrogen atom and N2 molecule, and the activation barriers for the dissociation and formation of N2 in Ge2Sb2Te5 were calculated by ab‐initio methods. Various transition and metastable states were found along the migration pathway. Migration barrier energies up to 1.19 eV for the nitrogen atom suggest that it is difficult for it to move from one site to any other site or diffuse out from Ge2Sb2Te5 although doped nitrogen is energetically less stable with respect to N2 in vacuum. N2 in Ge2Sb2Te5 was hardly expected to dissociate into nitrogen atoms and vice versa. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
95.
96.
Chul Eui Kim Jong Seol Yoon Hae Jin Hwang 《Journal of Sol-Gel Science and Technology》2009,49(1):47-52
A crack-free silica aerogel monolith was fabricated from a cheap water glass derived silicic acid solution by adding glycerol,
which served as a drying control chemical additive (DCCA). The OH surfaces of the wet gel with glycerol were modified using
a TMCS/n-hexane mixture followed by solvent exchange from water to n-hexane. The obtained surface modified wet gel was dried at 75 °C under ambient pressure. The addition of glycerol appears
to give the wet gel a more homogeneous microstructure (larger pore size and uniform size distribution) as well as enhanced
stiffness. However, glycerol also retards surface modification and solvent exchange. The aerogel synthesized with glycerol
added to the silica sol maintained a relatively low bulk density compared with the aerogels aged in a mixed ethanol (EtOH)/TEOS
solution. The reproducibility of aerogel production was further improved in the aerogel synthesized with glycerol added to
the silica sol and aged in a 70%EtOH/30%TEOS solution. 相似文献
97.
Changsheng Wu Helga U. vanderHeul Alexey V. Melnik Jens Lübben Pieter C. Dorrestein Adriaan J. Minnaard Young Hae Choi Gilles P. vanWezel 《Angewandte Chemie (International ed. in English)》2019,58(9):2809-2814
The angucyclines form the largest family of polycyclic aromatic polyketides, and have been studied extensively. Herein, we report the discovery of lugdunomycin, an angucycline‐derived polyketide, produced by Streptomyces species QL37. Lugdunomycin has unique structural characteristics, including a heptacyclic ring system, a spiroatom, two all‐carbon stereocenters, and a benzaza‐[4,3,3]propellane motif. Considering the structural novelty, we propose that lugdunomycin represents a novel subclass of aromatic polyketides. Metabolomics, combined with MS‐based molecular networking analysis of Streptomyces sp. QL37, elucidated 24 other rearranged and non‐rearranged angucyclines, 11 of which were previously undescribed. A biosynthetic route for the lugdunomycin and limamycins is also proposed. This work demonstrates that revisiting well‐known compound families and their producer strains still is a promising approach for drug discovery. 相似文献
98.
Soo‐Young Jeong Hae Won Jang Trishna Debnath Kwang‐Geun Lee 《Journal of separation science》2019,42(5):1012-1018
In this study, an automated solid‐phase microextraction coupled with gas chromatography and mass spectrometry method was developed and validated for the determination of furan in eight matrices including ham, milk, apple juice, rice porridge, peanut butter, flatfish, tuna (canned) and seaweed. The calibration curves were highly linear (r2 > 0.990) and the limit of detection and limit of quantification ranged from 0.01?0.02 and 0.04?0.06 ng/g, respectively. The recovery ranged from 77.81?111.47%. The validated method was used to analyse the furan levels in 120 foods. The highest levels of furan were detected in black tea (172.05 ng/g) and red ginseng extract (89.27 ng/g). Whelk (canned) contained a high furan content (21.34 ng/g) among the seafood samples. 相似文献
99.
We report the fabrication and performance of a lensed photonic crystal fiber (PCF) designed as a compact but effective side-viewing optical imaging probe. The lensed-PCF probe was implemented in a single body without using any other fibers or additional optics. The beam expansion region and a focusing ball lens, necessary for a focuser, were simultaneously formed along a small piece of PCF by applying arc discharges. The side-viewing ability was provided by polishing the ball lens with a femtosecond laser to form a total internal reflection surface. The working distance and the transverse resolution of the fabricated single-body lensed-PCF were experimentally measured to be 570 and 6.8 microm, respectively. With the proposed lensed-PCF probe, optical coherence tomography images of an in vitro biological sample were successfully obtained. 相似文献
100.
Ah-Reum Han Hae Ran Park Geum Jin Kim Bo-Ram Kim Ye-Ram Kim Hyeon Hwa Park Jisu Park Chang Hyun Jin Jung Min Kim Soon-Jae Kwon Jin-Baek Kim Shugeng Cao Joo-Won Nam Hyukjae Choi 《Molecules (Basel, Switzerland)》2021,26(24)
Lentil (Lens culinaris; Fabaceae), one of the major pulse crops in the world, is an important source of proteins, prebiotics, lipids, and essential minerals as well as functional components such as flavonoids, polyphenols, and phenolic acids. To improve crop nutritional and medicinal traits, hybridization and mutation are widely used in plant breeding research. In this study, mutant lentil populations were generated by γ-irradiation for the development of new cultivars by inducing genetic diversity. Molecular networking via Global Natural Product Social Molecular Networking web platform and dipeptidyl peptide-IV inhibitor screening assay were utilized as tools for structure-based discovery of active components in active mutant lines selected among the lentil population. The bioactivity-based molecular networking analysis resulted in the annotation of the molecular class of phosphatidylcholine (PC) from the most active mutant line. Among PCs, 1-stearoyl-2-hydroxy-sn-glycero-3-phosphocholine (18:0 Lyso PC) was selected for further in vivo study of anti-obesity effect in a high-fat diet (HFD)-induced obese mouse model. The administration of 18:0 Lyso PC not only prevented body weight gain and decreased relative gonadal adipose tissue weight, but also attenuated the levels of total cholesterol, triglycerides, low-density lipoprotein cholesterol, and leptin in the sera of HFD-induced obese mice. Additionally, 18:0 Lyso PC treatment inhibited the increase of adipocyte area and crown-like structures in adipose tissue. Therefore, these results suggest that 18:0 Lyso PC is a potential compound to have protective effects against obesity, improving obese phenotype induced by HFD. 相似文献