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| 1 | Toward point-of-care management of chronic respiratory conditions:Electrochemical sensing of nitrite content in exhaled breath condensate using reduced graphene oxide显示文摘We present a portable non-invasive approach for measuring indicators of inflammation and oxidative stress in the respiratory tract by quantifying a biomarker in exhaled breath condensate(EBC).We discuss the fabrication and characterization of a miniaturized electrochemical sensor for detecting nitrite content in EBC using reduced graphene oxide.The nitrite content in EBC has been demonstrated to be a promising biomarker of inflammation in the respiratory tract,particularly in asthma.We utilized the unique properties of reduced graphene oxide(rGO);specifically,the material is resilient to corrosion while exhibiting rapid electron transfer with electrolytes,thus allowing for highly sensitive electrochemical detection with minimal fouling.Our rGO sensor was housed in an electrochemical cell fabricated from polydimethyl siloxane(PDMS),which was necessary to analyze small EBC sample volumes.The sensor is capable of detecting nitrite at a low over-potential of 0.7 V with respect to an Ag/AgCl reference electrode.We characterized the performance of the sensors using standard nitrite/buffer solutions,nitrite spiked into EBC,and clinical EBC samples.The sensor demonstrated a sensitivity of 0.21μAμM^(−1) cm^(−2) in the range of 20–100μM and of 0.1μAμM^(−1) cm^(−2) in the range of 100–1000μM nitrite concentration and exhibited a low detection limit of 830 nM in the EBC matrix.To benchmark our platform,we tested our sensors using seven pre-characterized clinical EBC samples with concentrations ranging between 0.14 and 6.5μM.This enzyme-free and label-free method of detecting biomarkers in EBC can pave the way for the development of portable breath analyzers for diagnosing and managing changes in respiratory inflammation and disease. | Azam Gholizadeh Damien Voiry Clifford Weisel Andrew Gow Robert Laumbach Howard Kipen Manish Chhowalla Mehdi Javanmard | 2017 | Microsystems & Nanoengineering2017，3，1： | 5 |
| 2 | Critical Amino Acid Residues for Nicotine 5'-Hydroxylation in Human CYP2A Enzymes显示文摘Objective: We have continued previous work in which we demonstrated that #117 and #372 amino acids contrib- uted to the high activities of human CYP2A13 in catalyzing 4-methylnitrosamino-1-(3-pyridyl)-1-butanone(NNK) and aflatoxin B1(AFB1) carcinogenic activation. The present study was designed to identify other potential amino acid residues that contribute to the different catalytic characteristics of two CYP2A enzymes, CYP2A6 and CYP2A13, in nicotine metabolism and provide insights of the substrate and related amino acid residues interactions. Methods: A series of reciprocally substituted mutants of CYP2A6Ile300 → Phe, CYP2A6Gly301Ala, CYP2A6Ser369 → Gly, CYP2A13Phe300 → Ile, CYP2A13Ala301 → Gly and CYP2A13Gly369 → Ser were generated by site-directed mutagenesis/baculovirus-Sf9 insect cells expression. Comparative kinetic analysis of nicotine 5'hydroxylatin by wild type and mutant CYP2A proteins was performed. Results:All amino acid residue substitutions at 300, 301 and 369 caused significant kinetic property changes in nicotine metabolism. While CYP2A6Ile300 → Phe and CYP2A6Gly301→Ala mutations had notable catalytic efficiency increases compared to that for the wild type CYP2A6, CYP2A13Phe300→Ile and CYP2A13Ala301→Gly replacement introduced remarkable catalytic efficiency decreases. CteIunfYtf iaioPcdni2de Aiontif1co #3yn3G ,v 6ali9ylal 3 r6tae9h s→seiisdge uSn ecei afrsit.iac gClanyonitnfti cicKc leaumfns fdtiilcoeyinc ea:rn#fecf3aey0sc 0eate ,l vtd#ee 3rbra0sot1uitoh san KnVsd mmw a#axe 3nree6dn 9 chV aarmuenassxcei evddmau bleueysen iVstn,. m whaCxu hYvmialPaer2in aAt htCi6eoYS noePspr 2r3pa6A9oth→6sei/t1reG 3t h lepyafl fnaien yKcc tirmsme cawphsoeea rrnttegha eenss etc. e raSontual ewlbyssi tttiiinhc- nicotine 5'-oxidation. Switching #300 or #301 residues did not affect the CYP2A protein affinities toward nicotine, although these amino acids are located in the active center. Ser369 to Gly substitution indirectly affected nicotine binding by creating more space and conformational flexibility for the nearby residues, such as Leu370 which is crucial for many hydroxylations. | Xiaoyang Hea Xu Xu Jian Shen Li Sun Anthony Y. H. Lu Clifford Weisel Junyan Hong | 2008 | Journal of Nanjing Medical University2008，22，6： | 1 |
| 3 | Halogenated DBP concentrations in a distribution system 显示文摘 | Wei Jie Chen Clifford P Weisel | 1998 | Journal of American Water Works Association1998，90，4： | 1 |
| 4 | Computational fluid dynamics modeling of transport and deposition of pesticides in an aircraft cabin显示文摘 | Sastry S. Isukapalli Sagnik Mazumdar Pradeep George Binnian Wei Byron Jones Clifford P. Weisel | 2013 | Atmospheric Environment2013，，： | 1 |
| 5 | 第208位异亮氨酸对人细胞色素P4502A6尼古丁代谢活性的影响显示文摘目的探讨人体尼古丁主要代谢酶细胞色素P450(CYP)2A6及其同族成员CYP2A13肽链结构中,影响其尼古丁5′-羟化代谢活性的关键性氨基酸残基。方法使用前期制备的CYP2A6和CYP2A13系列氨基酸互换突变体:CYP2A6V117A,CYP2A6G164H,CYP2A6I208S,CYP2A6R372H和CYP2A6S465P以及CYP2A13A117V,CYP2A13H164G,CYP2A13S208I,CYP2A13H372R和CYP2A13P465S,比较其与相应野生蛋白酶的尼古丁5′-羟化催化反应的动力学参数。结果各突变体对2个CYP2A蛋白酶的尼古丁代谢活性影响不同。对于CYP2A6,I208S突变对酶活性的影响显著,导致表观反应常数Km及最大反应速度Vmax由野生型62.25μmol.L-1和6.53mol.min-1.mol-1变化为345μmol.L-1和2.19mol.min-1.mol-1,但该位点对CYP2A13酶活性无显著影响;对于CYP2A13,H372R突变对酶活性的影响最为显著,导致Km及Vmax由野生型的26.01μmol.L-1和24.51mol.min-1.mol-1变为148.7μmol.L-1和6.11mol.min-1.mol-1,此位点对CYP2A6无显著影响。其他位点突变对酶活性影响较小或不显著。结论CYP2A家族蛋白中,I208与H372分别是影响CYP2A6和CYP2A13对尼古丁代谢的关键残基。对于同家族蛋白酶而言,关键性氨基酸的作用并不总是一一对应。 | 何晓阳 王守林 徐旭 Clifford WEISEL 洪钧言 | 2009 | 中国药理学与毒理学杂志2009，23，6： | 0 |
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