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Chlorine reactivity

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https://www.readbyqxmd.com/read/28106994/enzymatic-halogenation-and-dehalogenation-reactions-pervasive-and-mechanistically-diverse
#1
Vinayak Agarwal, Zachary D Miles, Jaclyn M Winter, Alessandra S Eustáquio, Abrahim A El Gamal, Bradley S Moore
Naturally produced halogenated compounds are ubiquitous across all domains of life where they perform a multitude of biological functions and adopt a diversity of chemical structures. Accordingly, a diverse collection of enzyme catalysts to install and remove halogens from organic scaffolds has evolved in nature. Accounting for the different chemical properties of the four halogen atoms (fluorine, chlorine, bromine, and iodine) and the diversity and chemical reactivity of their organic substrates, enzymes performing biosynthetic and degradative halogenation chemistry utilize numerous mechanistic strategies involving oxidation, reduction, and substitution...
January 20, 2017: Chemical Reviews
https://www.readbyqxmd.com/read/28098448/new-insights-into-trihalomethane-and-haloacetic-acid-formation-potentials-correlation-with-the-molecular-composition-of-natural-organic-matter-in-source-water
#2
Xin Wang, Haifeng Zhang, Yahe Zhang, Quan Shi, Juan Wang, Jianwei Yu, Min Yang
Natural organic matter (NOM) represents the major source of precursors for disinfection byproducts (DBPs), such as trihalomethanes (THMs) and haloacetic acids (HAAs), formed during disinfection of drinking water, but the molecular composition and reactivity of NOM remain not well understood. In this study, electrospray ionization coupled to Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) was used to characterize the molecular composition of NOM of twenty source waters taken across China for the purpose of determining the major precursors of THMs and HAAs at molecular level...
January 18, 2017: Environmental Science & Technology
https://www.readbyqxmd.com/read/28095695/frontier-molecular-orbital-contributions-to-chlorination-versus-hydroxylation-selectivity-in-the-non-heme-iron-halogenase-syrb2
#3
Martin Srnec, Edward I Solomon
The ability of an Fe(IV)=O intermediate in SyrB2 to perform chlorination vs. hydroxylation was computationally evaluated for different substrates that had been studied experimentally. The π-trajectory for H-atom abstraction (Fe(IV)=O oriented perpendicular to the C-H bond of substrate) was found to lead to the S = 2 five-coordinate HO-Fe(III)-Cl complex with the C• of the substrate, π-oriented relative to both the Cl(-) and OH(-) ligands. From this ferric intermediate, hydroxylation is thermodynamically favored, but chlorination is intrinsically more reactive due to the energy splitting between two key redox-active dπ* frontier molecular orbitals (FMOs)...
January 18, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28087479/synthesis-and-characterization-of-gold-nanostructured-chorin-e6-for-photodynamic-therapy
#4
L Vieira, M L Castilho, I Ferreira, J Ferreira-Strixino, K C Hewitt, L Raniero
Photodynamic therapy is an alternative treatment for cancer based on cellular uptake of a photosensitizer, illuminated with an appropriate wavelength in the presence of oxygen. A cascade of reactions generates reactive oxygen species leading to cell death. Using carbodiimide chemistry, chlorin e6 (Ce6) was covalently bonded to thiourea, and (via the sulphur end group) to gold nanoparticles (AuNPs), forming the Ce6-AuNP complex. Ce6 absorbs in the range 650-680nm, where the coefficient of biological tissue absorption is low (part of the therapeutic window), which is ideal for biological application...
January 10, 2017: Photodiagnosis and Photodynamic Therapy
https://www.readbyqxmd.com/read/28075568/reaction-pathways-and-kinetics-of-a-cyanobacterial-neurotoxin-%C3%AE-n-methylamino-l-alanine-bmaa-during-chlorination
#5
Yiting Chen, Wan-Ru Chen, Zhiquan Liu, Tsair-Fuh Lin
β-N-Methylamino-L-alanine (BMAA), a probable cause of the amyotrophic lateral sclerosis/parkinsonism-dementia complex (ALS/PDC), or Alzheimer's disease, has been identified in more than 20 cyanobacterial genera. However, its removal and fate in drinking water has never been reported before. In this study, the reaction of BMAA with chlorine, a common drinking-water oxidant/disinfectant, was investigated. A liquid chromatograph coupled with a triple quadrupole mass spectrometer was employed to quantify BMAA and its intermediates...
January 11, 2017: Environmental Science & Technology
https://www.readbyqxmd.com/read/28070104/comparative-photodynamic-therapy-cytotoxicity-of-mannose-conjugated-chlorin-and-talaporfin-sodium-in-cultured-human-and-rat-cells
#6
Yo Shinoda, Tsutomu Takahashi, Jiro Akimoto, Megumi Ichikawa, Hiromi Yamazaki, Atsushi Narumi, Shigenobu Yano, Yasuyuki Fujiwara
Photodynamic therapy (PDT) is a Food and Drug Administration authorized method for cancer treatment, which uses photosensitizer and laser photo-irradiation to generate reactive oxygen species to induce cell death in tumors. Photosensitizers have been progressively developed, from first to third generation, with improvements in cell specificity, reduced side effects and toxicity, increased sensitivity for irradiation and reduced persistence of photosensitizer in healthy cells. These improvements have been achieved by basic comparative experiments between current and novel photosensitizers using cell lines; however, photosensitizers should be carefully evaluated because they may have cell type specificity...
2017: Journal of Toxicological Sciences
https://www.readbyqxmd.com/read/28067486/photo-cross-linkable-polymer-dots-with-stable-sensitizer-loading-and-amplified-singlet-oxygen-generation-for-photodynamic-therapy
#7
Ying Tang, Haobin Chen, Kaiwen Chang, Zhihe Liu, Yu Wang, Songnan Qu, Hong Xu, Changfeng Wu
Photodynamic therapy (PDT) is a promising treatment modality for clinical cancer therapy. However, the therapeutic effect of PDT is strongly dependent on the property of photosensitizer. Here, we developed photo-cross-linkable semiconductor polymer dots doped with photosensitizer Chlorin e6 (Ce6) to construct a nanoparticle platform for photodynamic therapy. Photoreactive oxetane groups were attached to the side chains of the semiconductor polymer. After photo-cross-linking reaction, the Ce6-doped Pdots formed an interpenetrated structure to prevent Ce6 leaching out from the Pdot matrix...
January 18, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28066950/pd-peppsi-ipentcl-a-useful-catalyst-for-the-coupling-of-2-aminopyridine-derivatives
#8
Michael G Organ, Abir Khadra, Stanislas Mayer
Pd-PEPPSI-IPentCl precatalyst has been demonstrated to be highly effective at the coupling of hetero(aryl)chlorides to free 2-aminopyridine substrates to produce N-(hetero)aryl-2-aminopyridine derivatives. The catalyst has proven competent in a number of other difficult cross-coupling reactions owing to the combination of the 3-penyl-substituted N-aryl groups and the chlorines on the backbone of the NHC core. This same reactivity here allows couplings to take place under very mild conditions (e.g., NaBHT or carbonate base) such that sensitive functional groups including esters, ketones, and nitriles are tolerated...
January 9, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28056449/transformation-of-aminopyrine-in-the-presence-of-free-available-chlorine-kinetics-products-and-reaction-pathways
#9
Mei-Quan Cai, Li Feng, Li-Qiu Zhang
Aminopyrine (AMP) has been frequently detected in the aquatic environment. In this study, the transformation mechanism of AMP by free available chlorine (FAC) oxidation was investigated. The results showed that FAC reacted with AMP rapidly, and a 74% elimination was achieved for 1.30 μM AMP after 2 min at 14.08 μM FAC dose. AMP chlorination was strongly pH-dependent, and its reaction included second- and third-order kinetic processes. Three active FAC species, including chlorine monoxide (Cl2O), molecular chlorine (Cl2), and hypochlorous acid (HOCl), were observed to contribute to AMP degradation...
December 26, 2016: Chemosphere
https://www.readbyqxmd.com/read/28032509/molecular-and-spectroscopic-characterization-of-water-extractable-organic-matter-from-thermally-altered-soils-reveal-insight-into-disinfection-byproduct-precursors
#10
Kaelin M Cawley, Amanda K Hohner, David C Podgorski, William T Cooper, Julie A Korak, Fernando L Rosario-Ortiz
To characterize the effects of thermal-alteration on water extractable organic matter (WEOM), soil samples were heated in a laboratory at 225, 350, and 500 °C. Next, heated and unheated soils were leached, filtered, and analyzed for dissolved organic carbon (DOC) concentration, optical properties, molecular size distribution, molecular composition, and disinfection byproduct (DBP) formation following the addition of chlorine. The soils heated to 225 °C leached the greatest DOC and had the highest C- and N-DBP precursor reactivity per unit carbon compared to the unheated material or soils heated to 350 or 500 °C...
December 29, 2016: Environmental Science & Technology
https://www.readbyqxmd.com/read/28026159/a-ratiometric-fluorescent-silicon-quantum-dots-ce6-complex-probe-for-the-live-cell-imaging-of-highly-reactive-oxygen-species
#11
Qianqian Zhao, Ren Zhang, Daixin Ye, Song Zhang, Hui Chen, Jilie Kong
The monitoring of reactive oxygen species (ROS) in living cells remains challenging, mainly due to the complexity, short half-life and autofluorescence of biological samples. In this work, we designed a ratiometric fluorescent probe for the detection and imaging of ROS, which was constructed from silicon quantum dots (Si QDs) with chlorin e6 (Ce6) through electrostatic attraction and showed well-resolved dual fluorescence emission signals (490 nm and 660 nm). Sensitive and selective biosensing of hydroxyl radical (•OH) was demonstrated based on fluorescence quenching of the Si QDs and Ce6 as an internal reference to avoid environmental interference, with a detection limit of ~0...
December 27, 2016: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28009922/luminescence-color-control-and-quantum-efficiency-enhancement-of-colloidal-si-nanocrystals-by-pulsed-laser-irradiation-in-liquid
#12
Ze Yuan, Toshihiro Nakamura, Sadao Adachi, Kiyoto Matsuishi
We demonstrate the emission color change of white-emitting chlorine-terminated silicon nanocrystals (Cl:Si-ncs) to blue-emitting carbon-terminated silicon nanocrystals (C:Si-ncs), together with the enhancement of the luminescence quantum efficiency from 7% to 13%, by post-laser ablation in 1-octene. Such changes of the PL properties are caused by the size reduction of Si-nc and efficient surface passivation by hydrocarbons, resulting from a high reactivity of 1-octene in the laser-ablation and subsequent nanoparticle-formation processes...
January 19, 2017: Nanoscale
https://www.readbyqxmd.com/read/28006704/combined-uv-treatment-and-ozonation-for-the-removal-of-by-product-precursors-in-swimming-pool-water
#13
Waqas A Cheema, Kamilla M S Kaarsholm, Henrik R Andersen
Both UV treatment and ozonation are used to reduce different types of disinfection by-products (DBPs) in swimming pools. UV treatment is the most common approach, as it is particularly efficient at removing combined chlorine. However, the UV treatment of pool water increases chlorine reactivity and the formation of chloro-organic DBPs such as trihalomethanes. Based on the similar selective reactivity of ozone and chlorine, we hypothesised that the created reactivity to chlorine, as a result of the UV treatment of dissolved organic matter in swimming pool water, might also be expressed as increased reactivity to ozone...
December 10, 2016: Water Research
https://www.readbyqxmd.com/read/27998787/formation-and-reactivity-of-inorganic-and-organic-chloramines-and-bromamines-during-oxidative-water-treatment
#14
Michèle B Heeb, Ina Kristiana, Daniela Trogolo, J Samuel Arey, Urs von Gunten
The formation and further reactions of halamines during oxidative water treatment can be relevant for water quality. In this study, we investigated the formation and reactivity of several inorganic and organic halamines (monochloramine, N-chloromethylamine, N-chlorodimethylamine, monobromamine, dibromamine, N-bromomethylamine, N,N-dibromomethylamine, and N-bromodimethylamine) by kinetic experiments, transformation product analysis, and quantum chemical computations. Kinetic model simulations were conducted to evaluate the relevance of halamines for various water treatment scenarios...
November 30, 2016: Water Research
https://www.readbyqxmd.com/read/27997135/subinhibitory-concentrations-of-disinfectants-promote-the-horizontal-transfer-of-multidrug-resistance-genes-within-and-across-genera
#15
Ye Zhang, April Z Gu, Miao He, Dan Li, Jianmin Chen
The greater abundances of antibiotic resistance genes (ARGs) in point-of-use tap and reclaimed water than that in freshly treated water raise the question whether residual disinfectants in distribution systems facilitate the spread of ARGs. This study investigated three widely used disinfectants (free chlorine, chloramine, and hydrogen peroxide) on promoting ARGs transfer within Escherichia coli strains and across genera from Escherichia coli to Salmonella typhimurium. The results demonstrated that subinhibitory concentrations (lower than minimum inhibitory concentrations [MICs]) of these disinfectants, namely 0...
January 3, 2017: Environmental Science & Technology
https://www.readbyqxmd.com/read/27993038/degradation-of-deet-and-caffeine-under-uv-chlorine-and-simulated-sunlight-chlorine-conditions
#16
Peizhe Sun, Wan-Ning Lee, Ruochun Zhang, Ching-Hua Huang
Photoactivation of aqueous chlorine could promote degradation of chlorine-resistant and photochemically stable chemicals accumulated in swimming pools. This study investigated the degradation of two such chemicals, N,N-diethyl-3-methylbenzamide (DEET) and caffeine, by low pressure ultraviolet (UV) light and simulated sunlight (SS) activated free chlorine (FC) in different water matrices. Both DEET and caffeine were rapidly degraded by UV/FC and SS/FC but exhibited different kinetic behaviors. The degradation of DEET followed pseudo-first-order kinetics, whereas the degradation of caffeine accelerated with reaction...
December 20, 2016: Environmental Science & Technology
https://www.readbyqxmd.com/read/27989134/stability-and-application-of-reactive-nitrogen-and-oxygen-species-induced-hemoglobin-modifications-in-dry-blood-spots-as-analyzed-by-liquid-chromatography-tandem-mass-spectrometry
#17
Hauh-Jyun Candy Chen, Chih-Huang Fan, Ya-Fen Yang
Dried blood spot (DBS) is an emerging microsampling technique for the bioanalysis of small molecules, including fatty acids, metabolites, drugs, and toxicants. DBS offers many advantages as a sample format including easy sample collection and cheap sample shipment. Hemoglobin adducts have been recognized as a suitable biomarker for monitoring chemical exposure. We previously reported that certain modified peptides in hemoglobin derived from reactive chlorine, nitrogen, and oxygen species are associated with factors including smoking, diabetes mellitus, and aging...
December 19, 2016: Chemical Research in Toxicology
https://www.readbyqxmd.com/read/27984131/enhanced-photo-geno-toxicity-of-demethylated-chlorpromazine-metabolites
#18
Fabrizio Palumbo, Guillermo Garcia-Lainez, Daniel Limones-Herrero, M Dolores Coloma, Javier Escobar, M Consuelo Jiménez, Miguel A Miranda, Inmaculada Andreu
Chlorpromazine (CPZ) is an anti-psychotic drug widely used to treat disorders such as schizophrenia or manic-depression. Unfortunately, CPZ exhibits undesirable side effects such as phototoxic and photoallergic reactions in humans. In general, the influence of drug metabolism on this type of these reactions has not been previously considered in photosafety testing. Thus, the present work aims to investigate the possible photo(geno)toxic potential of drug metabolites, using CPZ as an established reference compound...
October 27, 2016: Toxicology and Applied Pharmacology
https://www.readbyqxmd.com/read/27934265/cosolvent-effects-on-dechlorination-of-soil-sorbed-polychlorinated-biphenyls-using-bentonite-clay-templated-nanoscale-zero-valent-iron
#19
Kai Yu, G Daniel Sheng, Wesley McCall
Zero-valent iron synthesized using bentonite clay as a template (CZVI) was tested for its reactivity toward polychlorinated biphenyl (PCB) dechlorination in soil slurries. Aqueous-phase decachlorobiphenyl (PCB209) was rapidly dechlorinated by CZVI with a reaction rate 10 times greater than that by conventional nanoscale zerovalent iron. This superior reactivity was due largely to the nanoscale size (∼0.5 nm) of the ZVI particles located in the clay galleries. In soil slurries where PCB209 was strongly soil-bound, adding ethanol as an organic cosolvent led to increased PCB209 desorption into the liquid phase, thereby enhancing the PCB209 dechlorination with CZVI...
December 6, 2016: Environmental Science & Technology
https://www.readbyqxmd.com/read/27933980/nanoceria-mediated-drug-delivery-for-targeted-photodynamic-therapy-on-drug-resistant-breast-cancer
#20
Hong Li, Cong Liu, Yi-Ping Zeng, Yu-Hui Hao, Jia-Wei Huang, Zhang-You Yang, Rong Li
Photodynamic therapy (PDT) has shown great potential for overcoming drug-resistant cancers. Here, we report a multifunctional drug delivery system based on chlorin e6 (Ce6)/folic acid (FA)-loaded branched polyethylenimine-PEGylation ceria nanoparticles (PPCNPs-Ce6/FA), which was developed for targeted PDT to overcome drug-resistant breast cancers. Nanocarrier delivery and FA targeting significantly promoted the cellular uptake of photosensitizers (PSs), followed by their accumulation in lysosomes. PPCNPs-Ce6/FA generated reactive oxygen species (ROS) after near-infrared irradiation (NIR, 660 nm), leading to reduced P-glycoprotein (P-gp) expression, lysosomal membrane permeabilization (LMP), and excellent phototoxicity toward resistant MCF-7/ADR cells, even at ultralow doses...
November 23, 2016: ACS Applied Materials & Interfaces
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