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121.
Joseph P. Gaut Jaeman Byun Hung D. Tran Jay W. Heinecke 《Analytical biochemistry》2002,300(2):252-259
Halogenation and nitration of biomolecules have been proposed as key mechanisms of host defense against bacteria, fungi, and viruses. Reactive oxidants also have the potential to damage host tissue, and they have been implicated in disease. In the current studies, we describe specific, sensitive, and quantitative methods for detecting three stable markers of oxidative damage: 3-chlorotyrosine, 3-bromotyrosine, and 3-nitrotyrosine. Our results indicate that electron capture-negative chemical ionization-gas chromatography/mass spectrometry (EC-NCI GC/MS) is 100-fold more sensitive than liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-MS/MS) for analyzing authentic 3-chlorotyrosine, 3-bromotyrosine, and 3-nitrotyrosine. Using an isotopomer of tyrosine to evaluate artifactual production of the analytes during sample preparation and analysis, we found that artifact generation was negligible with either technique. However, LC-MS/MS proved cumbersome for analyzing multiple samples because it required 1.5 h of run and equilibration time per analysis. In contrast, EC-NCI GC/MS required only 5 min of run time per analysis. Using EC-NCI GC/MS, we were able to detect and quantify attomole levels of free 3-chlorotyrosine, 3-bromotyrosine, and 3-nitrotyrosine in human plasma. Our results indicate that EC-NCI GC/MS is a sensitive and specific method for quantifying free 3-chlorotyrosine, 3-bromotyrosine, and 3-nitrotyrosine in biological fluids in a single, rapid analysis and that it avoids generating any of the analytes ex vivo. 相似文献
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The PEGylated gelatin nanoparticles were prepared by self-assembling method and characterized. The gelatin drug carrier was
proposed as a targeting drug delivery system with the hypothesis that the gelatin carrier could be degraded by the matrix
metalloprotease (MMP) and release the anticancer drug loaded inside carriers around the cancer site. The gelatin nanoparticles
proposed in this study were composed of deoxycholic acid (DOCA), monomethoxy polyethylene glycol (MPEG), and gelatin. The
carboxyl groups of DOCA and carboxylated MPEG were coupled with amine group of gelatin by dichlorohexylcarbodiimide (DCC)
method. One molecule of gelatin coupled with 205 molecules of MPEG and 275 molecules of DOCA. The synthesized gelatin/DOCA/MPEG
conjugates (GDM) were ultrasonicated to produce self-assembled nanoparticles. DOCA acted as the hydrophobic core, thereby
aggregating gelatin molecules and hydrophilic MPEG chains located at the surface of the nanoparticles. The concentration of
GDM, intensity of sonication, sonication time and temperature, all affected to control the particle size in the ultrasonication.
The optimum condition was obtained as 1.0 mg/mL of GDM, 28 W for sonication intensity, 3 min of sonication time, and room
temperature. The size distribution of particle was found to be 100–1000 nm in this condition. The particles which had a broad
size distribution were filtered by 0.2 μm membrane. The product yield of particles having below 200 nm of size was about 30%.
After filtration, an average diameter of GDM nanoparticle was 176 nm (155–200 nm). 相似文献
124.
Jun-Kyu Byun John A. Vu Siou-Luan He Jyan-Chyun Jang Karin Musier-Forsyth 《The Journal of biological chemistry》2022,298(9)
Faithful translation of the genetic code is critical for the viability of all living organisms. The trans-editing enzyme ProXp-ala prevents Pro to Ala mutations during translation by hydrolyzing misacylated Ala-tRNAPro that has been synthesized by prolyl-tRNA synthetase. Plant ProXp-ala sequences contain a conserved C-terminal domain (CTD) that is absent in other organisms; the origin, structure, and function of this extra domain are unknown. To characterize the plant-specific CTD, we performed bioinformatics and computational analyses that provided a model consistent with a conserved α-helical structure. We also expressed and purified wildtype Arabidopsis thaliana (At) ProXp-ala in Escherichia coli, as well as variants lacking the CTD or containing only the CTD. Circular dichroism spectroscopy confirmed a loss of α-helical signal intensity upon CTD truncation. Size-exclusion chromatography with multiangle laser-light scattering revealed that wildtype At ProXp-ala was primarily dimeric and CTD truncation abolished dimerization in vitro. Furthermore, bimolecular fluorescence complementation assays in At protoplasts support a role for the CTD in homodimerization in vivo. The deacylation rate of Ala-tRNAPro by At ProXp-ala was also significantly reduced in the absence of the CTD, and kinetic assays indicated that the reduction in activity is primarily due to a tRNA binding defect. Overall, these results broaden our understanding of eukaryotic translational fidelity in the plant kingdom. Our study reveals that the plant-specific CTD plays a significant role in substrate binding and canonical editing function. Through its ability to facilitate protein–protein interactions, we propose the CTD may also provide expanded functional potential for trans-editing enzymes in plants. 相似文献
125.
Hoang Vu Phan Quoc Viet Nguyen Quang Tri Truong Tien Van Truong Hoon Cheol Park Nam Seo Goo Doyoung Byun Min Jun Kim 《仿生工程学报(英文版)》2012,9(4):391-401
We briefly summarized how to design and fabricate an insect-mimicking flapping-wing system and demonstrate how to implement inherent pitching stability for stable vertical takeoff.The effect of relative locations of the Center of Gravity (CG) and the mean Aerodynamic Center (AC) on vertical flight was theoretically examined through static force balance consideration.We conducted a series of vertical takeoff tests in which the location of the mean AC was determined using an unsteady Blade Element Theory (BET) previously developed by the authors.Sequential images were captured during the takeoff tests using a high-speed camera.The results demonstrated that inherent pitching stability for vertical takeoff can be achieved by controlling the relative position between the CG and the mean AC of the flapping system. 相似文献
126.
127.
Azhar Muhammad Quoc Viet Nguyen Hoon Cheol Park Do Y.Hwang Doyoung Byun Nam Seo Goo 《仿生工程学报(英文版)》2010,7(2):134-141
<正> In an attempt to realize a flapping wing micro-air vehicle with morphing wings, we report on improvements to our previousfoldable artificial hind wing.Multiple hinges, which were implemented to mimic the bending zone of a beetle hind wing, weremade of small composite hinge plates and tiny aluminum rivets.The buck-tails of rivets were flared after the hinge plates wereassembled with the rivets so that the folding/unfolding motions could be completed in less time, and the straight shape of theartificial hind wing could be maintained after fabrication.Folding and unfolding actions were triggered by electrically-activatedShape Memory Alloy (SMA) wires.For wing folding, the actuation characteristics of the SMA wire actuator were modifiedthrough heat treatment.Through a series of flapping tests, we confirmed that the artificial wings did not fold back and arbitrarilyfluctuate during the flapping motion. 相似文献
128.
Hye Suck An Jang Wook Lee Woo Jin Kim Hyun Jeong Lim Eun Mi Kim Soon Gyu Byun Young Baek Hur Jung Youn Park Jeong In Myeong Chul Min An 《Genes & genomics.》2013,35(6):805-815
The Pacific oyster, Crassostrea gigas, is the most important and valuable commercial fishery species in Korea. Its farming started 20 years ago and is still rapid expansion in Korea. In this study, to maintain the genetic diversity of this valuable marine resource, possible genetic similarity and differences between the wild population and hatchery population in Tongyeong, Korea were accessed using multiplex assays with nine highly polymorphic microsatellite loci. A total of 250 different alleles were found over all loci. Despite a long history of hatchery practices, very high levels of polymorphism (mean alleles = 22.89 and mean heterozygosity = 0.92) were detected between the two populations. No statistically significant reductions were found in heterozygosity or allelic diversity in the hatchery population compared with the wild population. However, significant genetic heterogeneity was found between two populations. These results provide no evidence to show that hatchery practice of Pacific oyster in Korea has significantly affected the genetic variability of the hatchery stock. Although further studies are needed for comprehensive determinations of the hatchery and wild populations with increased number of Pacific oyster sample collections, information on the genetic variation and differentiation obtained in this study can be applied for genetic monitoring of aquaculture stocks, genetic improvement by selective breeding and designing of more efficient conservation management guidelines for these valuable genetic materials. 相似文献
129.
130.
Seulgi Lee Bernie Byeonghoon Park Hongmok Kwon Vitchan Kim Jang Su Jeon Rowoon Lee Milan Subedi Taehyeong Lim Hyunsoo Ha Dongju An Jaehoon Kim Donghak Kim Sang Kyum Kim Seyun Kim Youngjoo Byun 《Journal of enzyme inhibition and medicinal chemistry》2022,37(1):269
Inositol hexakisphosphate kinase (IP6K) is an important mammalian enzyme involved in various biological processes such as insulin signalling and blood clotting. Recent analyses on drug metabolism and pharmacokinetic properties on TNP (N2-(m-trifluorobenzyl), N6-(p-nitrobenzyl)purine), a pan-IP6K inhibitor, have suggested that it may inhibit cytochrome P450 (CYP450) enzymes and induce unwanted drug-drug interactions in the liver. In this study, we confirmed that TNP inhibits CYP3A4 in type I binding mode more selectively than the other CYP450 isoforms. In an effort to find novel purine-based IP6K inhibitors with minimal CYP3A4 inhibition, we designed and synthesised 15 TNP analogs. Structure-activity relationship and biochemical studies, including ADP-Glo kinase assay and quantification of cell-based IP7 production, showed that compound 9 dramatically reduced CYP3A4 inhibition while retaining IP6K-inhibitory activity. Compound 9 can be a tool molecule for structural optimisation of purine-based IP6K inhibitors. 相似文献