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81.
Protein AMPylation is an emerging post-translational modification, which plays key roles in bacterial pathogenesis and cell biology. Enzymes with AMPylation activity, referred to as AMPylators, have been identified in several bacterial pathogens and eukaryotes. To facilitate the study of this unique modification, we developed an alkynyl chemical reporter for detection and identification of protein AMPylation substrates. Covalent functionalization of AMPylation substrates with the alkynyl reporter in lieu of adenylyl 5'-monophosphate (AMP) allows their subsequent bioorthogonal ligation with azide-fluorescent dyes or affinity enrichment tags. We show that this chemical reporter is transferred by a range of AMPylators onto their cognate protein substrates and allows rapid detection and identification of AMPylated substrates. 相似文献
82.
Guaiacol and its analogs, a distinct flavor in whiskey, foods, and beverages, display different inclusion complexes with α‐Cyclodextrin (α‐CD) and can be detected on a Nafion modified boron‐doped diamond (BDD) electrode. The stable Nafion layer preconcentrates the analyte‐α‐CD complexes prior to electroanalysis by square wave voltammetry (SWV) to enhance detection sensitivities. This sensing mode together with peak deconvolution successfully distinguishes between guaiacol, 4‐ethylguaiacol (4‐EG), three cresol isomers, and phenols in a popular whiskey brand. The results obtained are corroborated by high‐performance liquid chromatography (HPLC). Anodic oxidation at + 2 V in phosphate buffer, pH 7 is proven as an effective method to renew the electrode surface after its exposure to the guaiacols. This robust approach circumvents several drawbacks associated with the use of enzymes and nanomaterials for the analysis of such analytes as reported in the literature. 相似文献
83.
Keith B. Male Mahsa HamzehJohnny Montes Alfred C.W. LeungJohn H.T. Luong 《Analytica chimica acta》2013
Titanium dioxide (TiO2) nanoparticles (NPs) with different sizes and structures were probed for plausible cytotoxicity using electric cell-substrate impedance sensing (ECIS), a non-invasive and on-line procedure for continuous monitoring of cytotoxicity. For insect cells (Spodoptera frugiperda Sf9), the ECIS50 values, i.e., the concentration required to achieve 50% inhibition of the response, differed depending on the size and shape of the TiO2 nanostructure. The lowest ECIS50 value (158 ppm) was observed for the needle shaped rutile TiO2 (10 nm × 40 nm, 15.5 nm nominal particle size), followed by 211 ppm for P-25 (34.1 nm, 80% anatase and 20% rutile), 302 ppm for MTI5 (5.9 nm, 99% anatase) and 417 ppm for Hombitan LW-S bulk TiO2 (169.5 nm, 99% anatase). Exposure of TiO2 NPs to UV light at 254 nm or 365 nm exhibited no significant effect on the ECIS50 value due to the aggregation of TiO2 NPs with diminishing photocatalytic activities. Chinese hamster lung fibroblast V79 cells, exhibited no significant cytotoxicity/inhibition up to 400 ppm with P25, MTI5 and bulk TiO2. However, a noticeable inhibitory effect was observed (ECIS50 value of 251 ppm) with rutile TiO2 as cell spreading on the electrode surface was prevented 相似文献
84.
A practical gas chromatographic approach is introduced for the characterization of trace ethylene glycol in industrial solvents and lubricants. The analytical approach employs single step derivatization technique that effectively converts ethylene glycol to the cyclic boronate ester (2-phenyl-1,3,2-dioxaborolane), using phenyl boronic acid as a derivatizing reagent. The separation of the derivatized product was achieved by using multidimensional gas chromatography. Heavy lubricant matrices like engine crankcase oil were back-flushed to improve sample throughput and system cleanliness. Detection and quantitation of 2-phenyl-1,3,2-dioxaborolane was conducted with mass spectrometry in selected ion monitoring mode. 相似文献
85.
Minh Phong Luong 《Particle & Particle Systems Characterization》1993,10(2):79-85
The paper discusses the interest in conventional triaxial tests widely used in soil mechanics for a better understanding of both the mechanical behaviour and flow characteristics of granular bulk materials. It proposes a rheological characterization of granular foodstuffs on diverse types of stress path using a conventional triaxial cell. The characteristic state concept, defining the disaggregation threshold of the granular structure, is found to be suitable and even indispensible for examining the mechanical behaviour and the flowability of stored bulk materials. The experimental results readily suggest, as an indicator of the arching effect, a rheological index that characterizes the particle interlocking breakdown and hence the flowability of the stored materials. In addition, this study offers a realistic physical meaning for parameters in use in constitutive models (yield conditions and flow rules) when describing granular flow in various hopper geometries. The case of silos equipped with vibrating hoppers necessitates additionally the study of the rheological behaviour of materials under cyclic and vibratory loadings in order to analyse the processes of densification or disaggregation conditioning the flowability of the stored materials during emptying operations. 相似文献
86.
The Plasma Membrane as a Reservoir,Protective Shield,and Light‐Triggered Launch Pad for Peptide Therapeutics
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Colin P. O'Banion Dr. Luong T. Nguyen Prof. Qunzhao Wang Prof. Melanie A. Priestman Prof. Stephen P. Holly Prof. Leslie V. Parise Prof. David S. Lawrence 《Angewandte Chemie (International ed. in English)》2016,55(3):950-954
Although peptide‐based therapeutics are finding increasing application in the clinic, extensive structural modification is typically required to prevent their rapid degradation by proteases in the blood. We have evaluated the ability of erythrocytes to serve as reservoirs, protective shields (against proteases), and light‐triggered launch pads for peptides. We designed lipidated peptides that are anchored to the surface of red blood cells, which furnishes a protease‐resistant environment. A photocleavable moiety is inserted between the lipid anchor and the peptide backbone, thereby enabling light‐triggered peptide release from erythrocytes. We have shown that a cell‐permeable peptide, a hormone (melanocyte stimulating hormone), and a blood‐clotting agent can be anchored to erythrocytes, protected from proteases, and photolytically released to create the desired biological effect. 相似文献
87.
Ultra‐trace analysis of furanic compounds in transformer/rectifier oils with water extraction and high‐performance liquid chromatography
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Monica Lin Kham Lin Amanda Lin Ronda Gras Jim Luong 《Journal of separation science》2016,39(14):2777-2784
A novel approach for the determination of parts‐per‐billion level of 5‐hydroxymethyl‐2‐furaldehyde, furfuryl alcohol, furfural, 2‐furyl methyl ketone, and 5‐methylfurfural in transformer or rectifier oils has been successfully innovated and implemented. Various extraction methods including solid‐phase extraction, liquid–liquid extraction using methanol, acetonitrile, and water were studied. Water was by far the most efficient solvent for use as an extraction medium. Separation of the analytes was conducted using a 4.6 mm × 250 mm × 3.5 μm Agilent Zorbax column while detection and quantitation were conducted with a variable wavelength UV detector. Detection limits of all furans were at 1 ppb v/v with linear ranges range from 5 to 1000 ppb v/v with correlation coefficients of 0.997 or better. A relative standard deviation of at most 2.4% at 1000 ppb v/v and 7.3% at 5 ppb v/v and a recovery from 43% to 90% depending on the analyte monitored were obtained. The method was purposely designed to be environmental friendly with water as an extraction medium. Also, the method uses 80% water and 20% acetonitrile with a mere 0.2 mL/min of acetonitrile in an acetonitrile/water mixture as mobile phase. The analytical technique has been demonstrated to be highly reliable with low cost of ownership, suitable for deployment in quality control labs or in regions where available analytical resources and solvents are difficult to procure. 相似文献
88.
Raman-based detection of bacteria using silver nanoparticles conjugated with antibodies 总被引:1,自引:0,他引:1
Surface enhanced Raman scattering (SERS) has been used to detect bacteria captured by polyclonal antibodies sorbed onto protein-A-modified silver nanoparticles. The selectivity and discrimination of the technique were assured by using a specific antibody to the model bacterium, Escherichia coli. As the SERS enhancement mechanism depends upon the metal surface proximity, 8 nm was considered as the optimum distance between the bacterium and the nanoparticle surface. Spectral reproducibility was verified using Principal Components Analysis to differentiate the clusters corresponding to the biomolecules and/or bacteria sorbed onto nanoparticles. Compared to the normal Raman spectrum, the SERS technique resulted in an intensity enhancement of over 20-fold. 相似文献
89.
Huda Alghamdi Majidah Alsaeedi Dr. Alyah Buzid Prof. Jeremy D. Glennon Prof. John H. T. Luong 《Electroanalysis》2021,33(5):1137-1142
Benzalkonium chloride (BAK) is a mixture of alkyl benzyl dimethyl ammonium chlorides, which is used primarily as a biocide, surfactant, preservative, and antimicrobial agent in the pharmaceutical industry, in particular in ophthalmologic and nasal solutions. However, BAK may cause harmful consequences on the eye structures of the anterior segment. Control of BAK identity and content is necessary by applying a sensitive detection method. This study unravels the use of a glassy carbon (GC) electrode and a pristine boron-doped diamond electrode (BDD) for the detection of four BAK homologs in a non-aqueous medium using square wave voltammetry (SWV). The BDD provided more reproducibility of the oxidation potential than GC with a correlation coefficient of 0.999. The irreversible oxidation peak was very broad and deconvoluted into 3 peaks corresponding to C12, C14, and combined C16–C18 to reflect their concentration ratio in the mixture. The method was then extended to the detection of the C12 homolog in the ophthalmic formulations with a limit of detection (LOD) of 0.4 μg/mL. The estimated BAK levels in three ophthalmic formulations were in agreement with the specified values by the manufacturers. The results were validated by high-performance liquid chromatography (HPLC) with ultraviolet (UV) detection, confirming the presence of a single homolog (C12) in the eye drops. 相似文献
90.
Suliman Al-Homidan Qamrul Hasan Ansari Luong Van Nguyen 《Journal of Optimization Theory and Applications》2017,175(3):683-701
In this paper, we study the weak sharp solutions for nonsmooth variational inequalities and give a characterization in terms of error bound. Some characterizations of solution set of nonsmooth variational inequalities are presented. Under certain conditions, we prove that the sequence generated by an algorithm for finding a solution of nonsmooth variational inequalities terminates after a finite number of iterates provided that the solutions set of a nonsmooth variational inequality is weakly sharp. We also study the finite termination property of the gradient projection method for solving nonsmooth variational inequalities under weak sharpness of the solution set. 相似文献