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https://www.readbyqxmd.com/read/29156559/tocotrienols-a-family-of-molecules-with-specific-biological-activities
#1
REVIEW
Raffaella Comitato, Roberto Ambra, Fabio Virgili
Vitamin E is a generic term frequently used to group together eight different molecules, namely: α-, β-, γ- and δ-tocopherol and the corresponding tocotrienols. The term tocopherol and eventually Vitamin E and its related activity was originally based on the capacity of countering foetal re-absorption in deficient rodents or the development of encephalomalacia in chickens. In humans, Vitamin E activity is generally considered to be solely related to the antioxidant properties of the tocolic chemical structure...
November 18, 2017: Antioxidants (Basel, Switzerland)
https://www.readbyqxmd.com/read/29151676/jim-hyde-and-the-endor-connection-a-personal-account
#2
Klaus Möbius, Wolfgang Lubitz, Anton Savitsky
In this minireview, we report on our year-long EPR work, such as electron-nuclear double resonance (ENDOR), pulse electron double resonance (PELDOR) and ELDOR-detected NMR (EDNMR) at X-band and W-band microwave frequencies and magnetic fields. This report is dedicated to James S. Hyde and honors his pioneering contributions to the measurement of spin interactions in large (bio)molecules. From these interactions, detailed information is revealed on structure and dynamics of macromolecules embedded in liquid-solution or solid-state environments...
2017: Applied Magnetic Resonance
https://www.readbyqxmd.com/read/29133257/comparative-efficacy-of-colonoscope-distal-attachment-devices-in-increasing-rates-of-adenoma-detection-a-network-meta-analysis
#3
REVIEW
Antonio Facciorusso, Valentina Del Prete, Rosario Vincenzo Buccino, Nicola Della Valle, Maurizio Cosimo Nacchiero, Fabio Monica, Renato Cannizzaro, Nicola Muscatiello
BACKGROUND & AIMS: Several add-on devices have been developed to increase rates of colon adenoma detection (ADR). We assessed their overall and comparative efficacy, and estimated absolute magnitude of benefit through a network meta-analysis. METHODS: We searched the PubMed/Medline and Embase database through March 2017 and identified 25 randomized controlled trials (comprising 16,103 patients) that compared the efficacy of add-on devices (cap, Endocuff, and Endorings) with each other or with standard colonoscopy...
November 10, 2017: Clinical Gastroenterology and Hepatology
https://www.readbyqxmd.com/read/29119650/thermally-activated-delayed-fluorescence-in-y3n-c80-endohedral-fullerene-time-resolved-luminescence-and-electron-paramagnetic-resonance-studies
#4
Michal Zalibera, Denis S Krylov, Dimitrios Karagiannis, Paul-Anton Will, Frank Ziegs, Sandra Schiemenz, Wolfgang Lubitz, Sebastian Reineke, Anton Savitsky, Alexey Alexandrovich Popov
Endohedral fullerene Y3N@C80 exhibits luminescence with reasonable quantum yield and extraordinary long lifetime. By variable-temperature steady-state and time-resolved luminescence spectroscopy, we demonstrate that above 60 K the Y3N@C80 exhibits thermally-activated delayed fluorescence with maximum emission at 120 K and a negligible prompt fluorescence. Below 60 K, a phosphorescence with a lifetime of 192 ms is observed. Spin distribution and dynamics in the triplet excited state is investigated with X- and W-band EPR and ENDOR spectroscopies and DFT computations...
November 9, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/29090577/probing-ligand-exchange-in-the-p450-enzyme-cyp121-from-mycobacterium-tuberculosis-dynamic-equilibrium-of-the-distal-heme-ligand-as-a-function-of-ph-and-temperature
#5
Andrew J Fielding, Kednerlin Dornevil, Li Ma, Ian Davis, Aimin Liu
CYP121 is a cytochrome P450 enzyme from Mycobacterium tuberculosis that catalyzes the formation of a C-C bond between the aromatic groups of its cyclodityrosine substrate (cYY). The crystal structure of CYP121 in complex with cYY reveals that the solvent-derived ligand remains bound to the ferric ion in the enzyme-substrate complex. Whereas in the generally accepted P450 mechanism, binding of the primary substrate in the active-site triggers the release of the solvent-derived ligand, priming the metal center for reduction and subsequent O2 binding...
November 20, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/29035062/determination-of-the-complete-spin-density-distribution-in-13-c-labeled-protein-bound-radical-intermediates-using-advanced-2d-electron-paramagnetic-resonance-spectroscopy-and-density-functional-theory
#6
Alexander T Taguchi, Patrick J O'Malley, Colin A Wraight, Sergei A Dikanov
Determining the complete electron spin density distribution for protein-bound radicals, even with advanced pulsed electron paramagnetic resonance (EPR) methods, is a formidable task. Here we present a strategy to overcome this problem combining multifrequency HYSCORE and ENDOR measurements on site-specifically (13)C-labeled samples with DFT calculations on model systems. As a demonstration of this approach, pulsed EPR experiments are performed on the primary QA and secondary QB ubisemiquinones of the photosynthetic reaction center from Rhodobacter sphaeroides (13)C-labeled at the ring and tail positions...
October 31, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/29034914/local-water-sensing-water-exchange-in-bacterial-photosynthetic-reaction-centers-embedded-in-a-trehalose-glass-studied-using-multiresonance-epr
#7
Anna Nalepa, Marco Malferrari, Wolfgang Lubitz, Giovanni Venturoli, Klaus Möbius, Anton Savitsky
Using isotope labeled water (D2O and H2(17)O) and pulsed W-band (94 GHz) high-field multiresonance EPR spectroscopies, such as ELDOR-detected NMR and ENDOR, the biologically important question of detection and quantification of local water in proteins is addressed. A bacterial reaction center (bRC) from Rhodobacter sphaeroides R26 embedded into a trehalose glass matrix is used as a model system. The bRC hosts the two native radical cofactor ions (primary electron donor) and (primary electron acceptor) as well as an artificial nitroxide spin label site-specifically attached to the surface of the H-protein domain...
October 25, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/29030789/foreign-bodies-in-sigmoid-colon-diverticulosis
#8
REVIEW
Ellen Ross, Patricia McKenna, John H Anderson
This review addresses the management of sigmoid colon diverticular disease associated with foreign bodies. In addition, two novel cases are presented. One case describes the management of diverticular bleeding secondary to a chicken bone and the other case reports retrieval of a retained EndoRings™ Device. The review identified 40 relevant publications including 50 subjects. Foreign bodies within sigmoid diverticular disease may be associated with inflammation, perforation, abscess and fistula. In current practice, diagnosis is often achieved with CT scan...
October 13, 2017: Clinical Journal of Gastroenterology
https://www.readbyqxmd.com/read/28989623/endor-characterization-of-an-iron-alkene-complex-provides-insight-into-a-corresponding-organometallic-intermediate-of-nitrogenase
#9
Masaki Horitani, Katarzyna Grubel, Sean F McWilliams, Bryan D Stubbert, Brandon Q Mercado, Ying Yu, Prabhuodeyara M Gurubasavaraj, Nicholas S Lees, Patrick L Holland, Brian M Hoffman
A bio-organometallic intermediate, denoted PA, was previously trapped during the reduction of propargyl alcohol to allyl alcohol (AA) by nitrogenase, and a similar one was trapped during acetylene reduction, representing foundational examples of alkene binding to a metal center in biology. ENDOR spectroscopy led to the conclusion that these intermediates have η(2) binding of the alkene, with the hydrogens on the terminal carbon structurally/magnetically equivalent and related by local mirror symmetry. However, our understanding of both the PA intermediate, and of the dependability of the ENDOR analysis on which this understanding was based, was constrained by the absence of reference iron-alkene complexes for EPR/ENDOR comparison...
September 1, 2017: Chemical Science
https://www.readbyqxmd.com/read/28933856/understanding-the-coordination-modes-of-cu-acac-2-imidazole-n-1-2-adducts-by-epr-endor-hyscore-and-dft-analysis
#10
Nadine Ritterskamp, Katherine Sharples, Emma Richards, Andrea Folli, Mario Chiesa, James A Platts, Damien M Murphy
The interaction of imidazole with a [Cu(acac)2] complex was studied using electron paramagnetic resonance (EPR), electron nuclear double resonance (ENDOR), hyperfine sublevel correlation spectroscopy (HYSCORE), and density functional theory (DFT). At low Im ratios (Cu:Im 1:10), a 5-coordinate [Cu(acac)2Imn=1] monoadduct is formed in frozen solution with the spin Hamiltonian parameters g1 = 2.063, g2 = 2.063, g3 = 2.307, A1 = 26, A2 = 15, and A3 = 472 MHz with Im coordinating along the axial direction. At higher Im concentrations (Cu:Im 1:50), a 6-coordinate [Cu(acac)2Imn=2] bis-adduct is formed with the spin Hamiltonian parameters g1 = 2...
October 2, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28892584/evidence-of-organic-luminescent-centers-in-sol-gel-synthesized-yttrium-aluminum-borate-matrix-leading-to-bright-visible-emission
#11
Pauline Burner, Atul D Sontakke, Mathieu Salaün, Michel Bardet, Jean-Marie Mouesca, Serge Gambarelli, Anne-Laure Barra, Alban Ferrier, Bruno Viana, Alain Ibanez, Vincent Maurel, Isabelle Gautier-Luneau
Yttrium aluminum borate (YAB) powders prepared by sol-gel process have been investigated to understand their photoluminescence (PL) mechanism. The amorphous YAB powders exhibit bright visible PL from blue emission for powders calcined at 450 °C to broad white PL for higher calcination temperature. Thanks to (13) C labelling, NMR and EPR studies show that propionic acid initially used to solubilize the yttrium nitrate is decomposed into aromatic molecules confined within the inorganic matrix. DTA-TG-MS analyses show around 2 wt % of carbogenic species...
September 11, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28829916/in-quest-of-the-alanine-r3-radical-multivariate-epr-spectral-analyses-of-x-irradiated-alanine-in-the-solid-state
#12
Eirik O Jåstad, Turid Torheim, Kathleen M Villeneuve, Knut Kvaal, Eli O Hole, Einar Sagstuen, Eirik Malinen, Cecilia M Futsaether
The amino acid l-α-alanine is the most commonly used material for solid-state electron paramagnetic resonance (EPR) dosimetry, due to the formation of highly stable radicals upon irradiation, with yields proportional to the radiation dose. Two major alanine radical components designated R1 and R2 have previously been uniquely characterized from EPR and electron-nuclear double resonance (ENDOR) studies as well as from quantum chemical calculations. There is also convincing experimental evidence of a third minor radical component R3, and a tentative radical structure has been suggested, even though no well-defined spectral signature has been observed experimentally...
September 19, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28798920/new-device-to-implement-the-adenoma-detection-rate
#13
REVIEW
Maddalena Zippi, Wandong Hong, Pietro Crispino, Giampiero Traversa
It is well-known that colonoscopy is considered the gold standard for colon cancer prevention. Although performed by experienced endoscopists, the matter remains of polyps missed during this examination. The reasons may include the size, shape and location of the lesions. Many colorectal cancer screening programs have been proposed to increase the adenoma detection rate. The substantial difference between these methods is whether the improvement in vision, particularly the detection of irregularities of the mucosa, is inside the endoscope electronic components (magnification, wide-angle vision, narrow band imaging, flexible spectral imaging colour enhancement, i-Scan) or outside the same, by the use of specific caps (EndoCuff, EndoVision, EndoRings)...
July 16, 2017: World Journal of Clinical Cases
https://www.readbyqxmd.com/read/28768413/monovalent-cation-activation-of-the-radical-sam-enzyme-pyruvate-formate-lyase-activating-enzyme
#14
Krista A Shisler, Rachel U Hutcheson, Masaki Horitani, Kaitlin S Duschene, Adam V Crain, Amanda S Byer, Eric M Shepard, Ashley Rasmussen, Jian Yang, William E Broderick, Jessica L Vey, Catherine L Drennan, Brian M Hoffman, Joan B Broderick
Pyruvate formate-lyase activating enzyme (PFL-AE) is a radical S-adenosyl-l-methionine (SAM) enzyme that installs a catalytically essential glycyl radical on pyruvate formate-lyase. We show that PFL-AE binds a catalytically essential monovalent cation at its active site, yet another parallel with B12 enzymes, and we characterize this cation site by a combination of structural, biochemical, and spectroscopic approaches. Refinement of the PFL-AE crystal structure reveals Na(+) as the most likely ion present in the solved structures, and pulsed electron nuclear double resonance (ENDOR) demonstrates that the same cation site is occupied by (23)Na in the solution state of the as-isolated enzyme...
August 30, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28715026/exchangeable-proton-endor-as-a-probe-of-the-redox-active-iron-center-in-activated-bleomycin-and-ferric-bleomycin
#15
Richard M Burger, Vladimir M Grigoryants, Charles P Scholes
Activated bleomycin (ABLM) is a drug-Fe(iii)-hydroperoxide complex kinetically competent in DNA attack (via H4' abstraction). This intermediate is relatively stable, but its spontaneous conversion to ferric bleomycin (Fe(iii)·BLM) is poorly characterized because no observable intermediate product accumulates. The Fe(iii)·BLM formed cryophotolytically from ABLM and kept at 77 K was remarkably similar by EPR and ENDOR criteria to Fe(iii)·BLM formed from Fe(iii) + BLM solution. The notable ENDOR criteria were the ENDOR frequencies and features of orientation-selected, strongly hyperfine-coupled, exchangeable protons associated with the environs of the iron within <3...
October 10, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28712805/direct-spectroscopic-detection-of-atp-turnover-reveals-mechanistic-divergence-of-abc-exporters
#16
Alberto Collauto, Smriti Mishra, Aleksei Litvinov, Hassane S Mchaourab, Daniella Goldfarb
We have applied high-field (W-band) pulse electron-nuclear double resonance (ENDOR) and electron-electron double resonance (ELDOR)-detected nuclear magnetic resonance (EDNMR) to characterize the coordination sphere of the Mn(2+) co-factor in the nucleotide binding sites (NBSs) of ABC transporters. MsbA and BmrCD are two efflux transporters hypothesized to represent divergent catalytic mechanisms. Our results reveal distinct coordination of Mn(2+) to ATP and transporter residues in the consensus and degenerate NBSs of BmrCD...
August 1, 2017: Structure
https://www.readbyqxmd.com/read/28678489/electronic-delocalization-in-the-radical-cations-of-porphyrin-oligomer-molecular-wires
#17
Martin D Peeks, Claudia E Tait, Patrik Neuhaus, Georg M Fischer, Markus Hoffmann, Renée Haver, Arjen Cnossen, Jeffrey R Harmer, Christiane R Timmel, Harry L Anderson
The radical cations of a family of π-conjugated porphyrin arrays have been investigated: linear chains of N = 1-6 porphyrins, a 6-porphyrin nanoring and a 12-porphyrin nanotube. The radical cations were generated in solution by chemical and electrochemical oxidation, and probed by vis-NIR-IR and EPR spectroscopies. The cations exhibit strong NIR bands at ∼1000 nm and 2000-5000 nm, which shift to longer wavelength with increasing oligomer length. Analysis of the NIR and IR spectra indicates that the polaron is delocalized over 2-3 porphyrin units in the linear oligomers...
August 2, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28668640/spectroscopic-studies-of-the-cytochrome-p450-reaction-mechanisms
#18
REVIEW
Piotr J Mak, Ilia G Denisov
The cytochrome P450 monooxygenases (P450s) are thiolate heme proteins that can, often under physiological conditions, catalyze many distinct oxidative transformations on a wide variety of molecules, including relatively simple alkanes or fatty acids, as well as more complex compounds such as steroids and exogenous pollutants. They perform such impressive chemistry utilizing a sophisticated catalytic cycle that involves a series of consecutive chemical transformations of heme prosthetic group. Each of these steps provides a unique spectral signature that reflects changes in oxidation or spin states, deformation of the porphyrin ring or alteration of dioxygen moieties...
June 28, 2017: Biochimica et Biophysica Acta
https://www.readbyqxmd.com/read/28640584/spectroscopic-evidence-for-a-h-bond-network-at-y356-located-at-the-subunit-interface-of-active-e-coli-ribonucleotide-reductase
#19
Thomas U Nick, Kanchana R Ravichandran, JoAnne Stubbe, Müge Kasanmascheff, Marina Bennati
The reaction catalyzed by E. coli ribonucleotide reductase (RNR) composed of α and β subunits that form an active α2β2 complex is a paradigm for proton-coupled electron transfer (PCET) processes in biological transformations. β2 contains the diferric tyrosyl radical (Y122·) cofactor that initiates radical transfer (RT) over 35 Å via a specific pathway of amino acids (Y122· ⇆ [W48] ⇆ Y356 in β2 to Y731 ⇆ Y730 ⇆ C439 in α2). Experimental evidence exists for colinear and orthogonal PCET in α2 and β2, respectively...
July 18, 2017: Biochemistry
https://www.readbyqxmd.com/read/28628313/tunneling-kinetics-and-nonadiabatic-proton-coupled-electron-transfer-in-proteins-the-effect-of-electric-fields-and-anharmonic-donor-acceptor-interactions
#20
Bridget Salna, Abdelkrim Benabbas, Douglas Russo, Paul M Champion
A proper description of proton donor-acceptor (D-A) distance fluctuations is crucial for understanding tunneling in proton-coupled electron transport (PCET). The typical harmonic approximation for the D-A potential results in a Gaussian probability distribution, which does not appropriately reflect the electronic repulsion forces that increase the energetic cost of sampling shorter D-A distances. Because these shorter distances are the primary channel for thermally activated tunneling, the analysis of tunneling kinetics depends sensitively on the inherently anharmonic nature of the D-A interaction...
July 11, 2017: Journal of Physical Chemistry. B
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