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https://www.readbyqxmd.com/read/28738658/an-ultrasensitive-chemiluminescence-aptasensor-for-thrombin-detection-based-on-iron-porphyrin-catalyzing-luminescence-desorbed-from-chitosan-modified-magnetic-oxide-graphene-composite
#1
Yuanling Sun, Yanhui Wang, Jianbo Li, Chaofan Ding, Yanna Lin, Weiyan Sun, Chuannan Luo
In this work, an ultrasensitive chemiluminescence (CL) aptasensor was prepared for thrombin detection based on iron porphyrin catalyzing luminol - hydrogen peroxide luminescence under alkaline conditions, and iron porphyrin was desorbed from chitosan modified magnetic oxide graphene composite (CS@Fe3O4@GO). Firstly, CS@Fe3O4@GO was prepared. CS@Fe3O4@GO has advantages of the good biocompatibility and positively charged on its surface of CS, the large specific surface area of GO and the easy separation characteristics of Fe3O4...
November 1, 2017: Talanta
https://www.readbyqxmd.com/read/28738649/well-defined-magnetic-surface-imprinted-nanoparticles-for-selective-enrichment-of-2-4-dichlorophenoxyacetic-acid-in-real-samples
#2
Le Sheng, Yulong Jin, Yonghuan He, Yanyan Huang, Liushui Yan, Rui Zhao
Superparamagnetic core-shell molecularly imprinted polymer nanoparticles (MIPs) were prepared via surface initiated reversible-addition fragmentation chain transfer (si-RAFT) polymerization for the selective recognition of 2,4-dichlorophenoxyacetic acid (2,4-D) in real samples. The construction of uniform core-shell structure with a 50nm MIP layer was successfully accomplished, which favored mass transfer and resulted in fast recognition kinetics. The static equilibrium experiments revealed the satisfied adsorption capacity and imprinting efficiency of Fe3O4@MIP...
November 1, 2017: Talanta
https://www.readbyqxmd.com/read/28738644/biosensor-for-the-characterisation-of-hmao-b-inhibitors-and-the-quantification-of-selegiline
#3
Maximilian Aigner, Patricia Preissegger, Kurt Kalcher, Eda Mehmeti, Peter Macheroux, Dale Edmondson, Astrid Ortner
A novel human monoamine oxidase B (hMAO B) based biosensor for inhibitory measurements was developed. It allows both the characterisation of the type of enzyme inhibition and the sensitive and simple determination of inhibitors like selegiline hydrochloride. The sensor consists of a screen printed carbon working electrode modified with 20% manganese dioxide (MnO2) and the enzyme hMAO B, which was immobilised on the electrode via a dialysis membrane (regenerated cellulose, molecular weight cut-off 14000). Inhibition of hMAO B is evaluated by adding different concentrations of the inhibitor selegiline hydrochloride to the enzyme and applying a defined amount of the hMAO B substrate phenylethylamine (PEA)...
November 1, 2017: Talanta
https://www.readbyqxmd.com/read/28738626/elimination-of-interference-from-water-in-kbr-disk-ft-ir-spectra-of-solid-biomaterials-by-chemometrics-solved-with-kinetic-modeling
#4
Sherald H Gordon, Rogers E Harry-O'kuru, Abdellatif A Mohamed
Infrared analysis of proteins and polysaccharides by the well known KBr disk technique is notoriously frustrated and defeated by absorbed water interference in the important amide and hydroxyl regions of spectra. This interference has too often been overlooked or ignored even when the resulting distortion is critical or even fatal, as in quantitative analyses of protein secondary structure, because the water has been impossible to measure or eliminate. Therefore, a new chemometric method was devised that corrects spectra of materials in KBr disks by mathematically eliminating the water interference...
November 1, 2017: Talanta
https://www.readbyqxmd.com/read/28738576/development-of-ph-responsive-polymer-and-citrate-aqueous-two-phase-system-for-extractive-bioconversion-of-cefprozil
#5
Jialing Chen, Zhaoyang Ding, Hongxia Pan, Xuejun Cao
A pH-responsive aqueous two-phase system (pH-ATPS) has been developed by sodium citrate and a recyclable pH-responsive polymer PADB6.8 that can response to the change of pH values. Phase separation mechanism is studied through Low field-NMR. All variables affecting the phase separation are evaluated. Phase characteristics (viscosity, density, interfacial tension) and phase separation kinetic are studied for understanding of separation process and operational parameters in applications. This pH-ATPS has the characters of low interfacial tension, high recovery leading efficient mass transfer and low cost...
November 1, 2017: Talanta
https://www.readbyqxmd.com/read/28738548/effect-of-thiosulfate-on-rapid-start-up-of-sulfur-based-reduction-of-high-concentrated-perchlorate-a-study-of-kinetics-extracellular-polymeric-substances-eps-and-bacterial-community-structure
#6
Jianbo Guo, Chao Zhang, Jing Lian, Caicai Lu, Zhi Chen, Yuanyuan Song, Yankai Guo, Yajuan Xing
Perchlorate (ClO4(-)) contamination is more and more concerned due to the hazards to humans. Based on the common primary bacterium (Helicobacteraceae) of both thiosulfate-acclimated sludge (T-Acc) and sulfur-acclimated sludge (S-Acc) for perchlorate reduction, the rapid start-up of sulfur-based perchlorate reduction reactor (SBPRR) was hypothesized by inoculating T-Acc. Furthermore, the performance of SBPRR, the SO4(2-) yield, kinetics of ClO4(-) reduction and the extracellular polymeric substances (EPS) of biofilm confirmed the hypothesis...
July 11, 2017: Bioresource Technology
https://www.readbyqxmd.com/read/28738510/degradation-kinetics-and-mechanism-of-sulfadiazine-and-sulfamethoxazole-in-an-agricultural-soil-system-with-manure-application
#7
Yu Zhang, Shuangqing Hu, Hongchang Zhang, Genxiang Shen, Zhejun Yuan, Wei Zhang
Recently, under the application of waste-water, manure and biosolids, antibiotics have been used massively in agriculture resulted in antibiotic resistance and potential environmental risks. In the present study, the removal of sulfadiazine (SDZ) and sulfamethoxazole (SMX) in an agricultural soil system was explored. All the experiments were conducted under different incubation conditions for 49days. The experimental results indicated that all the degradation processes could effectively follow a first-order kinetic model...
July 18, 2017: Science of the Total Environment
https://www.readbyqxmd.com/read/28738357/biphasically-modulating-the-activity-of-carboxypeptidase-g2-with-ultrasound
#8
Wanying Ma, Ying Zhang, Xueling Zheng, Tinghe Yu
BACKGROUND/AIMS: Carboxypeptidase G2 (CPG2) has been used for cancer prodrug therapy to realize the targeted release of active drugs, but there yet lacks a means to modulate the CPG2 activity. Here ultrasound was used to modulate the CPG2 activity. METHODS: The activity of insonated CPG2 was determined, and then underlying biochemical (i.e., monomer, dimer and conformation) and ultrasonic (i.e., heat and cavitation) mechanisms were explored. RESULTS: Ultrasound (1...
July 24, 2017: Cellular Physiology and Biochemistry
https://www.readbyqxmd.com/read/28738289/germinal-center-enhancement-by-extended-antigen-availability
#9
REVIEW
Kimberly M Cirelli, Shane Crotty
Vaccine elicitation of protective antibody responses has proved difficult for a number of important human pathogens, including HIV-1. The amount of somatic hypermutation associated with the development of broadly neutralizing antibodies against HIV has not been achieved using conventional immunization strategies. An underexplored aspect of vaccine design is modulation of antigen kinetics. Immunization strategies with extended antigen availability have recently been shown to enhance humoral responses. In this review, we explore the mechanisms through which sustained antigen availability can enhance germinal center responses and the potency of antibody responses...
July 21, 2017: Current Opinion in Immunology
https://www.readbyqxmd.com/read/28738204/the-fate-of-sotalol-in-aqueous-chlorination-kinetics-mechanisms-and-ecotoxicity-assessment
#10
Wan Nor Adira Wan Khalit, Kheng Soo Tay
Unmetabolized pharmaceuticals often enter the water treatment plants and exposed to various treatment processes. Among these water treatment processes, disinfection is a process which involves the application of chemical oxidation to remove pathogen. Untreated pharmaceuticals from primary and secondary treatment have the potential to be exposed to the chemical oxidation process during disinfection. This study investigated the kinetics and mechanism of the degradation of sotalol during chlorination process. Chlorination with hypochlorous acid (HOCl) as main reactive oxidant has been known as one of the most commonly used disinfection methods...
July 21, 2017: Ecotoxicology and Environmental Safety
https://www.readbyqxmd.com/read/28738154/modifying-surface-chemistry-of-metal-oxides-for-boosting-dissolution-kinetics-in-water-by-liquid-cell-electron-microscopy
#11
Yue Lu, Jiguo Geng, Kuan Wang, Wei Zhang, Wenqiang Ding, Zhenhua Zhang, Shaohua Xie, Hongxing Dai, Fu-Rong Chen, Manling Sui
Dissolution of metal oxides is fundamentally important for understanding mineral evolution and micromachining oxide functional materials. In general, dissolution of metal oxides is a slow and inefficient chemical reaction. Here, by introducing oxygen deficiencies to modify the surface chemistry of oxides, we can boost the dissolution kinetics of metal oxides in water, as in situ demonstrated in a liquid environmental transmission electron microscope (LETEM). The dissolution rate constant significantly increases by 16-19 orders of magnitude, equivalently a reduction of 0...
July 24, 2017: ACS Nano
https://www.readbyqxmd.com/read/28738141/quantification-of-chemical-and-mechanical-effects-on-the-formation-of-g-quadruplex-and-i-motif-in-duplex-dna
#12
Sangeetha Selvam, Shankar Mandal, Hanbin Mao
Formation of biologically significant tetraplex DNA species, such as G-quadruplexes and i-motifs, is affected by chemical (ions and pH) and mechanical (superhelicity [σ] and molecular crowding) factors. Due to the extremely challenging experimental conditions, relative im-portance of these factors on tetraplex folding is unknown. In this work, we quantitatively evalu-ated the chemical and mechanical effects on the population dynamics of DNA tetraplexes in In-sulin Linked Polymorphic Region using magneto-optical tweezers...
July 24, 2017: Biochemistry
https://www.readbyqxmd.com/read/28737944/in-situ-generated-glycinyl-chloroaminals-for-a-one-pot-synthesis-of-non-proteinogenic-%C3%AE-amino-esters
#13
Shyam S Samanta, Stephane P Roche
An acetyl chloride-mediated cascade transformation involving a primary carbamate, ethyl glyoxylate and various types of nucleophiles is reported for the synthesis of orthogonally protected α-amino esters. These reactions proceeded rapidly to afford the pivotal α-chloroglycine intermediate in excellent yields which can be directly functionalized in situ with various types of nucleophiles. A mild and unique AcOH(cat.)/AcCl system was found to promote an autocatalytic-like condensation and facilitate the multicomponent assembly of non-proteinogenic α-amino esters...
July 24, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28737940/defining-the-structural-basis-for-allosteric-product-release-from-e-coli-dihydrofolate-reductase-using-nmr-relaxation-dispersion
#14
David Oyen, R Bryn Fenwick, Phillip C Aoto, Robyn L Stanfield, Ian A Wilson, H Jane Dyson, Peter E Wright
The rate-determining step in the catalytic cycle of E.coli dihydrofolate reductase is tetrahydrofolate (THF) product release, which can occur via an allosteric or an intrinsic pathway. The allosteric pathway, which becomes accessible when the reduced cofactor NADPH is bound, involves transient sampling of a higher energy conformational state, greatly increasing the product dissociation rate compared to the intrinsic pathway that obtains when NADPH is absent. Although the kinetics of this process are known, the enzyme structure and the THF product conformation in the transiently formed excited state remains elusive...
July 24, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28737938/heterogeneous-photooxidation-of-so2-in-the-presence-of-two-different-mineral-dust-particles-gobi-and-arizona-dust
#15
Jiyeon Park, Myoseon Jang, Zechen Yu
The impact of authentic mineral dust particles sourced from the Gobi Desert (GDD) on the kinetic uptake coefficient of SO2 was studied under varying environments (humidity, O3, and NOx) using both an indoor chamber and an outdoor chamber. There was a significant increase in the kinetic uptake coefficient of SO2 (ΥSO4(2-),light) for GDD particles under UV light compared to the value (ΥSO4(2-),dark) under dark conditions at various relative humidities (RH) ranging from 20% to 80%. In both the presence and absence of O3 and NOx, ΥSO4(2-),light and ΥSO4(2-),dark) greatly increased with increasing RH...
July 24, 2017: Environmental Science & Technology
https://www.readbyqxmd.com/read/28737937/asymmetric-hydrogen-bonding-catalysis-for-the-synthesis-of-dihydroquinazoline-containing-antiviral-letermovir
#16
Cheol K Chung, Zhijian Liu, Katrina Lexa, Teresa Andreani, Yingju Xu, Yining Ji, Daniel Adam DiRocco, Guy R Humphrey, Rebecca Tamra Ruck
A weak Brønsted acid-catalyzed asymmetric guanidine aza-conjugate addition reaction has been developed. C2-symmetric, dual hydrogen-bond donating bistriflamides are shown to be highly effective in activating α,β-unsaturated esters toward the intramolecular addition of a pendant guanidinyl nucleophile. Preliminary mechanistic investigation, including DFT calculations and kinetics studies, support a conjugate addition pathway as more favorable energetically than an alternative electrocyclization pathway. This methodology has been successfully applied to the synthesis of the 3,4-dihydroquinazoline-containing antiviral, Letermovir, and a series of analogues...
July 24, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28737918/reactive-inelastic-and-dissociation-processes-in-collisions-of-atomic-oxygen-with-molecular-nitrogen
#17
Fabrizio Esposito, Iole Armenise
We report the results of detailed calculations of reactive, inelastic and dissociative processes in collisions of atomic oxygen with molecular nitrogen in their respective electronic ground states. Cross sections are calculated as a function of collision energy in the range 0.001-10eV, considering the whole rovibrational ladder. Some problems related to the vibrational energy levels of the asymptotes of 3A" and 3A' potential energy surfaces used in this work are solved by an appropriate scaling at the level of cross sections...
July 24, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28737915/extended-study-on-crystal-growth-and-viscosity-in-ge-sb-se-bulk-glasses-and-thin-films
#18
Simona Martinkova, Jaroslav Barták, Petr Koštál, Jiri Malek, Hiroyo Segawa
Crystal growth rates in Ge18Sb28Se54 bulk glass and thin film were measured using optical and scanning electron microscopy under isothermal conditions. The studied temperature region was 255 - 346 °C and 254 - 286 °C for bulk glass and thin film, respectively. The compact crystalline layer growing from the surface into the amorphous core was formed in bulk glasses and no bulk crystallization was observed. In the case of thin films, needle-shape crystals were formed. The crystalline layer and needle-shape crystals grew linearly with time that corresponds to crystal growth controlled by the crystal-liquid interface kinetics...
July 24, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28737894/dual-role-of-gold-nanorods-inhibition-dissolution-of-a%C3%AE-fibrils-induced-by-near-ir-laser
#19
Swathi Sudhakar, Poornima Budime Santhosh, Ethayaraja Mani
Extracellular plaques of amyloid beta (Aβ) fibrils and neurofibrillary tangles are known to be associated with neurological diseases such as Alzheimer's. Studies have shown that spherical nanoparticles inhibit the formation of Aβ fibrils by intercepting the nucleation and growth pathways of fibrillation. In this report, gold nanorods (AuNR) are used to inhibit the formation of Aβ fibrils and the shape-dependent plasmonic properties of AuNR are exploited to faciliate faster dissolution of mature Aβ fibrils...
July 24, 2017: ACS Chemical Neuroscience
https://www.readbyqxmd.com/read/28737885/classics-in-chemical-neuroscience-memantine
#20
Shahrina Alam, Kaelyn Skye Lingenfelter, Aaron M Bender, Craig W Lindsley
Memantine was the first breakthrough medication for the treatment of moderate to severe Alzheimer's disease (AD) patients, and represents a fundamentally new mechanism of action (moderate-affinity, uncompetitive, voltage-dependent, N-methyl-D-aspartate (NMDA) receptor antagonist that exhibits fast on/off kinetics) to modulate glutamatergic dysfunction. Since its approval by the FDA in 2003, memantine, alone, and in combination with donepezil, has improved patient outcomes in terms of cognition, behavioral disturbances, daily functioning and delaying time to institutionalization...
July 24, 2017: ACS Chemical Neuroscience
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