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https://www.readbyqxmd.com/read/28108379/-dark-singlet-oxygen-and-epr-spin-trapping-as-convenient-tools-to-assess-photolytic-drug-degradation
#1
Peter Persich, Steven Hostyn, Céline Joie, Guy Winderickx, Jeroen Pikkemaat, Edwin P Romijn, Bert U W Maes
Forced degradation studies are an important tool for a systematic assessment of decomposition pathways and identification of reactive sites in active pharmaceutical ingredients (APIs). Two methodologies have been combined in order to provide a deeper understanding of singlet-oxygen related degradation pathways of APIs under light irradiation. Firstly, we report that a "dark" singlet oxygen test enables the investigation of drug reactivity towards singlet oxygen independently of photolytic irradiation processes...
January 17, 2017: Journal of Pharmaceutical Sciences
https://www.readbyqxmd.com/read/28107011/delocalization-of-coherent-triplet-excitons-in-linear-rigid-rod-conjugated-oligomers
#2
Christian Hintze, Patrick Korf, Frank Degen, Friederike Schütze, Stefan Mecking, Ulrich E Steiner, Malte Drescher
In this work, the triplet state delocalization in a series of monodisperse oligo(p-phenyleneethynylene)s (OPEs) is studied by pulsed electron paramagnetic resonance (EPR) and pulsed electron nuclear double resonance (ENDOR) determining zero-field splitting, optical spin polarization, and proton hyperfine couplings. Neither the zero-field splitting parameters nor the optical spin polarization change significantly with OPE chain length, in contrast to the hyperfine coupling constants, which showed a systematic decrease with chain length n according to a 2/(1+n) decay law...
January 20, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28106365/coordinatively-self-assembled-luminescent-gold-nanoparticles-fluorescence-turn-on-system-for-high-efficiency-passive-tumor-imaging
#3
Xuandi Lai, Lishan Tan, Xiulong Deng, Jinbin Liu, Aiqing Li, Jianyu Liu, Jianqiang Hu
A fluorescence turn-on system for highly efficient and prolonged tumor imaging has been established by Co2+-induced coordination self-assembly strategy, in which luminescent glutathione (GSH)-modified gold nanoparticles (LGAuNPs) are assembled into LGAuNPs assemblies (LGAuNPs-Co) through coordination bond between unoccupied orbit of Co2+ and lone pair electrons of GSH on the surface of LGAuNPs. The LGAuNPs-Co is sensitive to microenvironment pH and its quenched luminescence will be turned on in tumor tissues (acidic microenvironment), which behaves as a fluorescence turn-on system for passive tumor imaging...
January 20, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28103007/glutamate-350-plays-an-essential-role-in-conformational-gating-of-long-range-radical-transport-in-e-coli-class-ia-ribonucleotide-reductase
#4
Kanchana R Ravichandran, Ellen C Minnihan, Qinghui Lin, Kenichi Yokoyama, Alexander T Taguchi, Jimin Shao, Daniel G Nocera, JoAnne Stubbe
E. coli Ia ribonucleotide reductase is composed of two subunits that form an active α2β2 complex. The nucleoside diphosphate substrates (NDP) are reduced in α2, 35 Å from the essential diferric-tyrosyl radical (Y122•) cofactor in β2. The Y122• mediated oxidation of C439 in α2 occurs by a pathway (Y122 ↔ [W48] ↔ Y356 in β2 to Y731 ↔ Y730 ↔ C439 in α2) across the α/β interface. The absence of an α2β2 structure precludes insight into the location of Y356 and Y731 at the subunit interface...
January 19, 2017: Biochemistry
https://www.readbyqxmd.com/read/28098798/free-radical-scavenging-activity-of-drops-and-spray-containing-propolis-an-epr-examination
#5
Pawel Olczyk, Katarzyna Komosinska-Vassev, Pawel Ramos, Lukasz Mencner, Krystyna Olczyk, Barbara Pilawa
The influence of heating at a temperature of 50 °C and UV-irradiation of propolis drops and spray on their free radical scavenging activity was determined. The kinetics of interactions of the propolis samples with DPPH free radicals was analyzed. Interactions of propolis drops and propolis spray with free radicals were examined by electron paramagnetic resonance spectroscopy. A spectrometer generating microwaves of 9.3 GHz frequency was used. The EPR spectra of the model DPPH free radicals were compared with the EPR spectra of DPPH in contact with the tested propolis samples...
January 13, 2017: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
https://www.readbyqxmd.com/read/28098314/isoindoline-nitroxide-labeled-porphyrins-as-potential-fluorescence-suppressed-spin-probes
#6
F Liu, T J Zou, Z L Tan, S Chen, Z H Wu, G P Yan, Q Zhang, S C Liang, J Yang
A series of isoindoline nitroxide-labeled porphyrins were synthesized by the reaction of 5-phenyldipyrromethane and 5-(4'-carboethoxy-methyleneoxyphenyl)dipyrromethane with 5-formyl-1,1,3,3-tetramethylisoindolin-2-yloxyl (FTMIO) using the Lindsey method. The corresponding water-soluble spin-labeled porphyrins were also prepared. Subsequently, these compounds were characterized and their in vitro properties were evaluated. The electrochemical assay demonstrated that these isoindoline nitroxide-labeled porphyrins had similar electrochemical and redox properties to 5-carboxy-1,1,3,3-tetramethylisoindolin-2-yloxyl (CTMIO)...
January 18, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28098267/a-tailored-multi-frequency-epr-approach-to-accurately-determine-the-magnetic-resonance-parameters-of-dynamic-nuclear-polarization-agents-application-to-amupol
#7
P Gast, D Mance, E Zurlo, K L Ivanov, M Baldus, M Huber
To understand the dynamic nuclear polarization (DNP) enhancements of biradical polarizing agents, the magnetic resonance parameters need to be known. We describe a tailored EPR approach to accurately determine electron spin-spin coupling parameters using a combination of standard (9 GHz), high (95 GHz) and ultra-high (275 GHz) frequency EPR. Comparing liquid- and frozen-solution continuous-wave EPR spectra provides accurate anisotropic dipolar interaction D and isotropic exchange interaction J parameters of the DNP biradical AMUPol...
January 18, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28097771/solution-synthesis-structure-and-co2-reduction-reactivity-of-a-scandium-ii-complex-sc-n-sime3-2-3
#8
David H Woen, Guo P Chen, Joseph W Ziller, Timothy J Boyle, Filipp Furche, William J Evans
The first crystallographically characterizable complex of Sc(2+) , [Sc(NR2 )3 ](-) (R=SiMe3 ), has been obtained by LnA3 /M reactions (Ln=rare earth metal; A=anionic ligand; M=alkali metal) involving reduction of Sc(NR2 )3 with K in the presence of 2.2.2-cryptand (crypt) and 18-crown-6 (18-c-6) and with Cs in the presence of crypt. Dark maroon [K(crypt)](+) , [K(18-c-6)](+) , and [Cs(crypt)](+) salts of the [Sc(NR2 )3 ](-) anion are formed, respectively. The formation of this oxidation state of Sc is also indicated by the eight-line EPR spectra arising from the I=7/2 (45) Sc nucleus...
January 18, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28094884/oxygen-delivery-as-a-limiting-factor-in-modelling-dicopper-ii-oxidase-reactivity
#9
Jana Gülzow, Gerald Hoerner, Peter Strauch, Anika Stritt, Elisabeth Irran, Andreas Grohmann
Ionisation of ligand-appended alkoxyl groups in mononuclear copper(II) complexes of N,O ligands L1 and L2, results in dinuclear complexes sharing symmetrical Cu2O2 cores. Mono- and binuclear complexes thus derived have been characterised with respect to molecular structure (XRD), electronic structure (UV-Vis, 1H-NMR, and EPR; density functional methods) and catalytic performance as models of catechol oxidase. The binuclear complexes with anti-ferromagnetically coupled copper(II) centres are moderately active in quinone formation from 3,5-di-tert-butyl-catechol under the established conditions of oxygen saturation, but are strongly activated when additional dioxygen is administered during catalytic turnover...
January 17, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28094367/formation-of-carbon-nanodots-with-different-spin-states-in-mechanically-processed-mixtures-of-zno-with-carbon-nanoparticles-an-electron-paramagnetic-resonance-study
#10
M Kakazey, M Vlasova, V Gómez-Vidales, A Ángeles-Pascual, V A Basiuk
Mixtures of zinc oxide with carbon nanoparticles, ZnO + xC (x = 0.1%, 1% and 3% by weight), were subjected to mechanical processing (MP) in a hermetically sealed grinding chamber. Using electron paramagnetic resonance (EPR) spectroscopy, we monitored the evolution of spin centers in CNPs. While the initial CNPs were EPR silent, their short-duration MP (tMP) gave rise to emergence of low-intensity carbon signal. Increasing the sample temperature at tMP > 9 min induced CNP oxidation, which lead to a dramatic increase in the intensity of C signal...
January 17, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28094364/effect-of-electron-spectral-diffusion-on-static-dynamic-nuclear-polarization-at-7-tesla
#11
Alisa Leavesley, Daphna Shimon, Ting Ann Siaw, Akiva Feintuch, Daniella Goldfarb, Shimon Vega, Ilia Kaminker, Songi Han
Here, we present an integrated experimental and theoretical study of (1)H dynamic nuclear polarization (DNP) of a frozen aqueous glass containing free radicals at 7 T, under static conditions and at temperatures ranging between 4 and 20 K. The DNP studies were performed with a home-built 200 GHz quasi-optics microwave bridge, powered by a tunable solid-state diode source. DNP using monochromatic and continuous wave (cw) irradiation applied to the electron paramagnetic resonance (EPR) spectrum of the radicals induces the transfer of polarization from the electron spins to the surrounding nuclei of the solvent and solutes in the frozen aqueous glass...
January 17, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28092786/imaging-thiol-redox-status-in-murine-tumors-in-vivo-with-rapid-scan-electron-paramagnetic-resonance
#12
Boris Epel, Subramanian V Sundramoorthy, Martyna Krzykawska-Serda, Matthew C Maggio, Mark Tseytlin, Gareth R Eaton, Sandra S Eaton, Gerald M Rosen, Joseph P Y Kao, Howard J Halpern
Thiol redox status is an important physiologic parameter that affects the success or failure of cancer treatment. Rapid scan electron paramagnetic resonance (RS EPR) is a novel technique that has shown higher signal-to-noise ratio than conventional continuous-wave EPR in in vitro studies. Here we used RS EPR to acquire rapid three-dimensional images of the thiol redox status of tumors in living mice. This work presents, for the first time, in vivo RS EPR images of the kinetics of the reaction of (2)H,(15)N-substituted disulfide-linked dinitroxide (PxSSPx) spin probe with intracellular glutathione...
December 31, 2016: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28089912/hiding-clinical-information-in-medical-images-a-new-high-capacity-and-reversible-data-hiding-technique
#13
Shabir A Parah, Farhana Ahad, Javaid A Sheikh, G M Bhat
A new high capacity and reversible data hiding scheme for e-healthcare applications has been presented in this paper. Pixel to Block (PTB) conversion technique has been used as an effective and computationally efficient alternative to interpolation for the cover image generation to ensure reversibility of medical images. A fragile watermark and Block Checksum (computed for each 4 × 4 block) have been embedded in the cover image for facilitating tamper detection and tamper localization, and hence content authentication at receiver...
January 12, 2017: Journal of Biomedical Informatics
https://www.readbyqxmd.com/read/28088630/support-dependent-active-species-formation-for-cuo-catalysts-leading-to-efficient-pollutant-degradation-in-alkaline-conditions
#14
Yibing Li, Lianshuang Guo, Dekang Huang, Ali Jawad, Zhuqi Chen, Jiakuan Yang, Weidong Liu, Yan Shen, Mingkui Wang, Guochuan Yin
Redox metal ions play the crucial role in versatile advanced oxidation technologies, in which controlling the active species formation through catalyst design is one of the key challenges in oxidant utilization. This work describes an example of different active species formations in CuO-mediated degradation just because of supporting material differences. Although three CuO catalysts were prepared by similar procedures, it was found that CuO-MgO catalyst demonstrated high efficiency in phenol degradation with bicarbonate activated H2O2, in which the superoxide radical is crucial, while hydroxyl radical and singlet oxygen are ignorable...
December 31, 2016: Journal of Hazardous Materials
https://www.readbyqxmd.com/read/28088569/design-of-%C3%AE-cyclodextrin-modified-tio2-nanotubes-for-the-adsorption-of-cu-ii-isotherms-and-kinetics-study
#15
Mohamed Triki, Haythem Tanazefti, Hafedh Kochkar
This paper builds on previous literature showing the interesting adsorptive properties of TiO2 nanotubes. It further explores the positive effect of β-cyclodextrin on these properties. Hence, β-cyclodextrin modified TiO2 nanotubes were successfully prepared and characterized by XRD, N2 physisorption at 77K, Raman, FTIR-ATR, (1)H NMR, TEM and EPR. The adsorptive interaction of Cu(II) with materials was investigated in aqueous solution at pH 9.25 (NH4(+)/NH3). The main conclusion is that copper(II)-ammonia complexation equilibria play an important role in the adsorption process...
January 10, 2017: Journal of Colloid and Interface Science
https://www.readbyqxmd.com/read/28081476/electron-spin-relaxation-of-a-boron-containing-heterocyclic-radical
#16
Sandra S Eaton, Kirby Huber, Hanan Elajaili, Joseph McPeak, Gareth R Eaton, Lauren E Longobardi, Douglas W Stephan
Preparation of the stable boron-containing heterocyclic phenanthrenedione radical, (C6F5)2B(O2C14H8), by frustrated Lewis pair chemistry has been reported recently. Electron paramagnetic resonance measurements of this radical were made at X-band in toluene:dichloromethane (9:1) from 10 to 293K, in toluene from 180 to 293K and at Q-band at 80K. In well-deoxygenated 0.1mM toluene solution at room temperature hyperfine splittings from (11)B, four pairs of (1)H, and 5 pairs of (19)F contribute to an EPR spectrum with many resolved lines...
December 30, 2016: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28079947/an-unusually-delocalized-mixed-valence-state-of-a-cyanidometal-bridged-compound-induced-by-thermal-electron-transfer
#17
Xiao Ma, Chen-Sheng Lin, Xiao-Quan Zhu, Sheng-Min Hu, Tian-Lu Sheng, Xin-Tao Wu
The heterometallic complexes trans-[Cp(dppe)FeNCRu(o-bpy)CNFe(dppe)Cp][PF6 ]n (1[PF6 ]n , n=2, 3, 4; o-bpy=1,2-bis(2,2'-bipyridyl-6-yl)ethane, dppe=1,2-bis(diphenylphosphino)ethane, Cp=1,3-cyclopentadiene) in three distinct states have been synthesized and fully characterized. 1(3+) [PF6 ]3 and 1(4+) [PF6 ]4 are the one- and two-electron oxidation products of 1(2+) [PF6 ]2 , respectively. The investigated results suggest that 1[PF6 ]3 is a Class II mixed valence compound. 1[PF6 ]4 after a thermal treatment at 400 K shows an unusually delocalized mixed valence state of [Fe(III) -NC-Ru(III) -CN-Fe(II) ], which is induced by electron transfer from the central Ru(II) to the terminal Fe(III) in 1[PF6 ]4 , which was confirmed by IR spectroscopy, magnetic data, and EPR and Mössbauer spectroscopy...
January 12, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28079373/energetics-of-the-s2-state-spin-isomers-of-the-oxygen-evolving-complex-of-photosystem-ii
#18
David J Vinyard, Sahr Khan, Mikhail Askerka, Victor S Batista, Gary W Brudvig
The S2 redox intermediate of the oxygen-evolving complex in Photosystem II is present as two spin isomers. The S = 1/2 isomer gives rise to a multiline EPR signal at g = 2, while the S = 5/2 isomer exhibits a broad EPR signal at g = 4.1. The electronic structures of these isomers are known, but their role in the catalytic cycle of water oxidation remains unclear. We show that formation of the S = 1/2 state from the S = 5/2 state is exergonic at temperatures above 160 K. However, the S = 1/2 isomer decays to S1 more slowly than the S = 5/2 isomer...
January 12, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28078892/dynamical-transitions-at-low-temperatures-in-the-nearest-hydration-shell-of-phospholipid-bilayers
#19
Victoria N Syryamina, Sergei Andreevich Dzuba
For the so-called dynamical transition from harmonic to anharmonic (or diffusive) motions in biological systems, the presence of hydration water is important. To explain the molecular mechanism of this transition, the information on molecular motions in the nearest hydration shell would be helpful. In this work, to study molecular motions in the nearest hydration shell of spin-labeled model biological membranes, a pulsed version of electron paramagnetic resonance (EPR)-electron spin echo envelope modulation (ESEEM) spectroscopy-is employed...
January 12, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28078740/simlabel-a-graphical-user-interface-to-simulate-continuous-wave-epr-spectra-from-site-directed-spin-labeling-experiments
#20
E Etienne, N Le Breton, M Martinho, E Mileo, V Belle
Site Directed Spin Labeling (SDSL) combined with continuous wave Electron Paramagnetic Resonance (cw EPR) spectroscopy is a powerful technique to reveal, at the residue level, structural transitions in proteins. SDSL-EPR is based on the selective grafting of a paramagnetic label on the protein under study, followed by cw EPR analysis. To extract valuable quantitative information from SDSL-EPR spectra and thus give reliable interpretation on biological system dynamics, numerical simulations of the spectra are required...
January 12, 2017: Magnetic Resonance in Chemistry: MRC
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