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Dynamic nuclear polarization

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https://www.readbyqxmd.com/read/28215095/ph-dependence-of-photoinduced-electron-transfer-with-ru-tap-3-2
#1
Ludovic Troian-Gautier, Epiphanie Mugeniwabagara, Luca Fusaro, Cécile Moucheron, Andrée Kirsch-De Mesmaeker, Michel Luhmer
The quenching of the excited state of [Ru(TAP)3](2+) (TAP = 1,4,5,8-tetraazaphenanthrene) by guanosine-5'-monophosphate (GMP), N-acetyltyrosine (N-Ac-Tyr), and hydroquinone (H2Q) has been studied in aqueous solution over a wide range of pH values including, for the first time, strongly acidic media. This quenching by electron transfer was examined by steady-state (1)H photochemically induced dynamic nuclear polarization (photo-CIDNP) as well as by more conventional techniques, among which are pulsed laser-induced transient absorption and emission experiments...
February 20, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28208473/non-hermitian-surface-hopping
#2
Xing Gao, Walter Thiel
We present a generalized non-Hermitian equation of motion (nH-EOM) to go beyond standard trajectory surface hopping dynamics. The derivation is based on the Born-Huang expansion of the total wave function and the polar representation of the nuclear factor. The nH-EOM contains two additional terms, a skew symmetry term iΓ with dissipation operator Γ to account for decoherence, and a kinetic-energy renormalization term to account for phase shifts, without destroying the invariance to the choice of representation...
January 2017: Physical Review. E
https://www.readbyqxmd.com/read/28201898/a-rayleighian-approach-for-modeling-kinetics-of-ionic-transport-in-polymeric-media
#3
Rajeev Kumar, Jyoti P Mahalik, Vera Bocharova, Eric W Stacy, Catalin Gainaru, Tomonori Saito, Mallory P Gobet, Steve Greenbaum, Bobby G Sumpter, Alexei P Sokolov
We report a theoretical approach for analyzing impedance of ionic liquids (ILs) and charged polymers such as polymerized ionic liquids (PolyILs) within linear response. The approach is based on the Rayleigh dissipation function formalism, which provides a computational framework for a systematic study of various factors, including polymer dynamics, in affecting the impedance. We present an analytical expression for the impedance within linear response by constructing a one-dimensional model for ionic transport in ILs/PolyILs...
February 14, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28195488/surface-sensitive-nmr-detection-of-the-sei-layer-on-reduced-graphene-oxide
#4
Michal Leskes, Gunwoo Kim, Tao Liu, Alison L Michan, Fabien Aussenac, Patrick Dorffer, Subhradip Paul, Clare P Grey
The solid electrolyte interphase (SEI) is detrimental for rechargeable batteries' performance and lifetime. Understanding its formation requires analytical techniques that provide molecular level insight. Here dynamic nuclear polarization (DNP) is utilized for the first time for enhancing the sensitivity of solid state NMR (ssNMR) spectroscopy to the SEI. The approach is demonstrated on reduced-graphene oxide (rGO) cycled in Li-ion cells in natural abundance and 13C-enriched electrolyte solvents. Our results indicate that DNP enhances the signal of outer SEI layers, enabling detection of natural abundance 13C spectra from this component of the SEI at reasonable timeframes...
February 14, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28194987/mass-defect-based-n-n-dimethyl-leucine-labels-for-quantitative-proteomics-and-amine-metabolomics-of-pancreatic-cancer-cells
#5
Ling Hao, Jillian Johnson, Christopher B Lietz, Amanda Buchberger, Dustin Frost, W John Kao, Lingjun Li
Mass spectrometry-based stable isotope labeling has become a key technology for protein and small-molecule analyses. We developed a multiplexed quantification method for simultaneous proteomics and amine metabolomics analyses via nano reversed-phase liquid chromatography-tandem mass spectrometry (nanoRPLC-MS/MS), called mass defect-based N,N-dimethyl leucine (mdDiLeu) labeling. The duplex mdDiLeu reagents were custom-synthesized with a mass difference of 20.5 mDa, arising from the subtle variation in nuclear binding energy between the two DiLeu isotopologues...
January 17, 2017: Analytical Chemistry
https://www.readbyqxmd.com/read/28191484/photoinduced-molecular-chirality-probed-by-ultrafast-resonant-x-ray-spectroscopy
#6
Jérémy R Rouxel, Markus Kowalewski, Shaul Mukamel
Recently developed circularly polarized X-ray light sources can probe the ultrafast chiral electronic and nuclear dynamics through spatially localized resonant core transitions. We present simulations of time-resolved circular dichroism signals given by the difference of left and right circularly polarized X-ray probe transmission following an excitation by a circularly polarized optical pump with the variable time delay. Application is made to formamide which is achiral in the ground state and assumes two chiral geometries upon optical excitation to the first valence excited state...
July 2017: Structural Dynamics (Melville, N.Y.)
https://www.readbyqxmd.com/read/28189087/a-ferromagnetic-shim-insert-for-nmr-magnets-towards-an-integrated-gyrotron-for-dnp-nmr-spectroscopy
#7
Herbert Ryan, Jan van Bentum, Thorsten Maly
In recent years high-field Dynamic Nuclear Polarization (DNP) enhanced NMR spectroscopy has gained significant interest. In high-field DNP-NMR experiments (⩾400MHz (1)H NMR, ⩾9.4T) often a stand-alone gyrotron is used to generate high microwave/THz power to produce sufficiently high microwave induced B1e fields at the position of the NMR sample. These devices typically require a second, stand-alone superconducting magnet to operate. Here we present the design and realization of a ferroshim insert, to create two iso-centers inside a commercially available wide-bore NMR magnet...
February 5, 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28183023/molecular-dynamics-based-selectivity-for-fast-field-cycling-relaxometry-by-overhauser-and-solid-effect-dynamic-nuclear-polarization
#8
Oliver Neudert, Carlos Mattea, Siegfried Stapf
In the last decade nuclear spin hyperpolarization methods, especially Dynamic Nuclear Polarization (DNP), have provided unprecedented possibilities for various NMR techniques by increasing the sensitivity by several orders of magnitude. Recently, in-situ DNP-enhanced Fast Field Cycling (FFC) relaxometry was shown to provide appreciable NMR signal enhancements in liquids and viscous systems. In this work, a measurement protocol for DNP-enhanced NMR studies is introduced which enables the selective detection of nuclear spin hyperpolarized by either Overhauser effect or solid effect DNP...
January 21, 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28165677/structure-of-the-sliding-clamp-from-the-fungal-pathogen-aspergillus-fumigatus-afumpcna-and-interactions-with-human-p21
#9
Andrew C Marshall, Alice J Kroker, Lauren A M Murray, Kahlia Gronthos, Harinda Rajapaksha, Kate L Wegener, John B Bruning
The fungal pathogen Aspergillus fumigatus has been implicated in a drastic increase in life-threatening infections over the past decade. However, compared to other microbial pathogens, little is known about the essential molecular processes of this organism. One such fundamental process is DNA replication. The protein responsible for ensuring processive DNA replication is PCNA (Proliferating Cell Nuclear Antigen, also known as the sliding clamp), which clamps the replicative polymerase to DNA. Here we present the first crystal structure of a sliding clamp from a pathogenic fungus (A...
February 6, 2017: FEBS Journal
https://www.readbyqxmd.com/read/28147646/hyperpolarization-of-nitrogen-15-nuclei-by-cross-polarization-and-dissolution-dynamic-nuclear-polarization
#10
Jonas Milani, Basile Vuichoud, Aurélien Bornet, Roberto Melzi, Sami Jannin, Geoffrey Bodenhausen
Dynamic Nuclear Polarization (DNP) is often achieved by the direct transfer of polarization from electrons to nuclei such as (13)C, induced by microwave saturation of the wings of narrow EPR lines of radicals like trityl. In the indirect approach on the other hand, DNP is used to transfer the polarization from the electrons of radicals such as nitroxides that have broad EPR lines to nuclear spins I = (1)H, followed by cross-polarization (CP) from I = (1)H to S = (13)C or other nuclei with low gyromagnetic ratios...
January 2017: Review of Scientific Instruments
https://www.readbyqxmd.com/read/28145700/synthetic-approach-to-determine-the-effect-of-nuclear-spin-distance-on-electronic-spin-decoherence
#11
Michael J Graham, Chung-Jui Yu, Matthew D Krzyaniak, Michael R Wasielewski, Danna E Freedman
Nuclear-electronic interactions are a fundamental phenomenon which impacts fields from magnetic resonance imaging to quantum information processing (QIP). The realization of QIP would transform diverse areas of research including accurate simulation of quantum dynamics and cryptography. One promising candidate for the smallest unit of QIP, a qubit, is electronic spin. Electronic spins in molecules offer significant advantages with regard to QIP, and for the emerging field of quantum sensing. Yet relative to other qubit candidates, they possess shorter superposition lifetimes, known as coherence times or T2, due to interactions with nuclear spins in the local environment...
February 15, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28128197/interfacial-ca-2-environments-in-nanocrystalline-apatites-revealed-by-dynamic-nuclear-polarization-enhanced-43-ca-nmr-spectroscopy
#12
Daniel Lee, César Leroy, Charlène Crevant, Laure Bonhomme-Coury, Florence Babonneau, Danielle Laurencin, Christian Bonhomme, Gaël De Paëpe
The interfaces within bones, teeth and other hybrid biomaterials are of paramount importance but remain particularly difficult to characterize at the molecular level because both sensitive and selective techniques are mandatory. Here, it is demonstrated that unprecedented insights into calcium environments, for example the differentiation of surface and core species of hydroxyapatite nanoparticles, can be obtained using solid-state NMR, when combined with dynamic nuclear polarization. Although calcium represents an ideal NMR target here (and de facto for a large variety of calcium-derived materials), its stable NMR-active isotope, calcium-43, is a highly unreceptive probe...
January 27, 2017: Nature Communications
https://www.readbyqxmd.com/read/28115611/cone-separation-quadratic-control-systems-and-control-of-spin-dynamics-in-the-presence-of-decoherence
#13
Navin Khaneja
In this paper, we study some control problems related to the control of coupled spin dynamics in the presence of relaxation and decoherence in nuclear magnetic resonance spectroscopy. The decoherence is modelled through a master equation. We study some model problems, whereby, through an appropriate choice of state variables, the system is reduced to a control system, where the state enters linearly and controls quadratically. We study this quadratic control system. Study of this system gives us explicit bounds on how close a coupled spin system can be driven to its target state and how much coherence and polarization can be transferred between coupled spins...
March 6, 2017: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
https://www.readbyqxmd.com/read/28112506/characterizing-substrate-surface-interactions-on-alumina-supported-metal-catalysts-by-dynamic-nuclear-polarization-enhanced-double-resonance-nmr-spectroscopy
#14
Frédéric A Perras, J Daniel Padmos, Robert L Johnson, Lin-Lin Wang, Thomas J Schwartz, Takeshi Kobayashi, J Hugh Horton, James A Dumesic, Brent H Shanks, Duane D Johnson, Marek Pruski
The characterization of nanometer-scale interactions between carbon-containing substrates and alumina surfaces is of paramount importance to industrial and academic catalysis applications, but it is also very challenging. Here, we demonstrate that dynamic nuclear polarization surface-enhanced NMR spectroscopy (DNP SENS) allows the unambiguous description of the coordination geometries and conformations of the substrates at the alumina surface through high-resolution measurements of (13)C-(27)Al distances. We apply this new technique to elucidate the molecular-level geometry of (13)C-enriched methionine and natural abundance poly(vinyl alcohol) adsorbed on γ-Al2O3-supported Pd catalysts, and we support these results with element-specific X-ray absorption near-edge measurements...
February 8, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28099013/dynamic-nuclear-polarization-signal-enhancement-with-high-affinity-biradical-tags
#15
Rivkah Rogawski, Ivan V Sergeyev, Yongjun Li, M Francesca Ottaviani, Virginia Cornish, Ann E McDermott
Dynamic nuclear polarization is an emerging technique for sensitizing solid-state NMR experiments by transferring polarization from electrons to nuclei. Stable biradicals, the polarization source for the cross effect mechanism, are typically codissolved at millimolar concentrations with proteins of interest. Here we describe the high-affinity biradical tag TMP-T, created by covalently linking trimethoprim, a nanomolar affinity ligand of dihydrofolate reductase (DHFR), to the biradical polarizing agent TOTAPOL...
February 6, 2017: Journal of Physical Chemistry. B
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
#16
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...
February 1, 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
#17
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...
February 1, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28093594/fast-and-accurate-mas-dnp-simulations-of-large-spin-ensembles
#18
Frédéric Mentink-Vigier, Shimon Vega, Gaël De Paëpe
A deeper understanding of parameters affecting Magic Angle Spinning Dynamic Nuclear Polarization (MAS-DNP), an emerging nuclear magnetic resonance hyperpolarization method, is crucial for the development of new polarizing agents and the successful implementation of the technique at higher magnetic fields (>10 T). Such progress is currently impeded by computational limitation which prevents the simulation of large spin ensembles (electron as well as nuclear spins) and to accurately describe the interplay between all the multiple key parameters at play...
February 1, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28078411/in-vitro-and-in-silico-assessment-of-the-structure-dependent-binding-of-bisphenol-analogues-to-glucocorticoid-receptor
#19
Jie Zhang, Tiehua Zhang, Tianzhu Guan, Hansong Yu, Tiezhu Li
Widespread use of bisphenol A (BPA) and other bisphenol analogues has attracted increasing attention for their potential adverse effects. As environmental endocrine-disrupting compounds (EDCs), bisphenols (BPs) may activate a variety of nuclear receptors, including glucocorticoid receptor (GR). In this work, the binding of 11 BPs to GR was investigated by fluorescence polarization (FP) assay in combination with molecular dynamics simulations. The human glucocorticoid receptor was prepared as a soluble recombinant protein...
January 11, 2017: Analytical and Bioanalytical Chemistry
https://www.readbyqxmd.com/read/28072398/transportable-hyperpolarized-metabolites
#20
Xiao Ji, Aurélien Bornet, Basile Vuichoud, Jonas Milani, David Gajan, Aaron J Rossini, Lyndon Emsley, Geoffrey Bodenhausen, Sami Jannin
Nuclear spin hyperpolarization of (13)C-labelled metabolites by dissolution dynamic nuclear polarization can enhance the NMR signals of metabolites by several orders of magnitude, which has enabled in vivo metabolic imaging by MRI. However, because of the short lifetime of the hyperpolarized magnetization (typically <1 min), the polarization process must be carried out close to the point of use. Here we introduce a concept that markedly extends hyperpolarization lifetimes and enables the transportation of hyperpolarized metabolites...
January 10, 2017: Nature Communications
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