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Dynamic nuclear polarization

Kendra K Frederick, Vladimir K Michaelis, Marc A Caporini, Loren B Andreas, Galia T Debelouchina, Robert G Griffin, Susan Lindquist
The yeast prion protein Sup35NM is a self-propagating amyloid. Despite intense study, there is no consensus on the organization of monomers within Sup35NM fibrils. Some studies point to a β-helical arrangement, whereas others suggest a parallel in-register organization. Intermolecular contacts are often determined by experiments that probe long-range heteronuclear contacts for fibrils templated from a 1:1 mixture of (13)C- and (15)N-labeled monomers. However, for Sup35NM, like many large proteins, chemical shift degeneracy limits the usefulness of this approach...
March 22, 2017: Proceedings of the National Academy of Sciences of the United States of America
Deni Mance, Johan van der Zwan, Marjolein E Z Velthoen, Florian Meirer, Bert M Weckhuysen, Marc Baldus, Eelco T C Vogt
A combination of solid-state NMR techniques supported by EPR and SEM-EDX experiments was used to localize different carbon species (coke) in commercial fluid catalytic cracking catalysts. Aliphatic coke species formed during the catalytic process and aromatic coke species deposited directly from the feedstock respond differently to dynamic nuclear polarization signal enhancement in integral and crushed FCC particles, indicating that aromatic species are mostly concentrated on the outside of the catalyst particles, whereas aliphatic species are also located on the inside of the FCC particles...
March 22, 2017: Chemical Communications: Chem Comm
Monu Kaushik, Mian Qi, Adelheid Godt, Björn Corzilius
High-spin complexes act as polarizing agents (PAs) for dynamic nuclear polarization (DNP) in solid-state NMR spectroscopy and feature promising aspects towards biomolecular DNP. We present a study on bis(Gd-chelate)s which enable cross effect (CE) DNP owing to spatial confinement of two dipolar-coupled electron spins. Their well-defined Gd⋅⋅⋅Gd distances in the range of 1.2-3.4 nm allowed us to elucidate the Gd⋅⋅⋅Gd distance dependence of the DNP mechanism and NMR signal enhancement. We found that Gd⋅⋅⋅Gd distances above 2...
March 20, 2017: Angewandte Chemie
L F Pinto, I Marín-Montesinos, V Lloveras, J L Muñoz-Gómez, M Pons, J Veciana, J Vidal-Gancedo
Herein, we report the synthesis and the study of a novel mixed biradical with BDPA and TEMPO radical units that are covalently bound by an ester group (BDPAesterTEMPO) as a polarizing agent for fast dissolution DNP. The biradical exhibits an extremely high DNP NMR enhancement of >50 000 times, which constitutes one of the largest signal enhancements observed so far, to the best of our knowledge.
March 17, 2017: Chemical Communications: Chem Comm
V Denysenkov, M Terekhov, R Maeder, S Fischer, S Zangos, T Vogl, T F Prisner
Here we describe a new hyperpolarization approach for magnetic resonance imaging applications at 1.5 T. Proton signal enhancements of more than 20 were achieved with a newly designed multimode microwave resonator situated inside the bore of the imager and used for Overhauser dynamic nuclear polarization of the water proton signal. Different from other approaches in our setup the hyperpolarization is achieved continuously by liquid water flowing through the polarizer under continuous microwave excitation. With an available flow rate of up to 1...
March 14, 2017: Scientific Reports
Ziang Li, Lindsay M Johnson, Ralm G Ricarte, Letitia J Yao, Marc A Hillmyer, Frank S Bates, Timothy P Lodge
Blends of hydroxypropyl methylcellulose acetate succinate (HPMCAS) and dodecyl (C12)-tailed poly(N-isopropylacrylamide) (PNIPAm) were systematically explored as a model system to dispense the active ingredient phenytoin by rapid dissolution, followed by the suppression of drug crystallization for an extended period. Dynamic and static light scattering revealed that C12-PNIPAm polymers, synthesized by reversible addition-fragmentation chain-transfer polymerization, self-assembled into micelles with dodecyl cores in phosphate-buffered saline (PBS, pH 6...
March 10, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Filippo Caracciolo, Pietro Carretta, Marta Filibian, Lucio Melone
1H dynamic nuclear polarization and nuclear spin-lattice relaxation rates have been studied in amorphous complexes of β -Cyclodextrins doped with different concentrations of TEMPO radical. Nuclear polarization increased up to 10 % in the optimal case, with a behavior of the build up rate ( 1/T_P OL ) and of the nuclear spin-lattice relaxation rate ( 1/T_1n ) consistent with a thermal mixing regime. The temperature dependence of 1/T_1n and its increase with the radical concentration indicate a relaxation process arising from the modulation of the electron-nucleus coupling by the glassy dynamics...
March 6, 2017: Journal of Physical Chemistry. B
Daniel A Starr, Lesilee S Rose
How LINC complexes are regulated to connect nuclei to the cytoskeleton during nuclear migration is unknown. Saunders et al. (2017. J. Cell Biol. show that the AAA+ ATPase torsinA and its partner LAP1 are required for nuclear migration during fibroblast polarization by mediating the dynamics of LINC complexes.
March 6, 2017: Journal of Cell Biology
Takeshi Kobayashi, Frédéric A Perras, Anna Murphy, Yao Yao, Jaclyn Catalano, Silvia A Centeno, Cecil Dybowski, Nicholas Zumbulyadis, Marek Pruski
Dynamic nuclear polarization (DNP) is used to enhance the (ultra)wideline (207)Pb solid-state NMR spectra of lead compounds of relevance in the preservation of cultural heritage objects. The DNP SSNMR experiments enabled, for the first time, the detection of the basic lead carbonate phase of the lead white pigment by (207)Pb SSNMR spectroscopy. Variable-temperature experiments revealed that the short T'2 relaxation time of the basic lead carbonate phase hinders the acquisition of the NMR signal at room temperature...
March 14, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
W Th Wenckebach
Dynamic Nuclear Polarization (DNP) via the mechanism of thermal mixing has proven itself most powerful for the orientation of nuclear spins in polarized targets and hyperpolarization for magnetic resonance imaging (MRI). Unfortunately, theoretical descriptions of this mechanism have been limited to using-at least partially-the high temperature approximation, in which Boltzmann factors are expanded linearly. However, the high nuclear spin polarization required and obtained for these applications does not justify such approximations...
February 20, 2017: Journal of Magnetic Resonance
Y-L Chung, M O Leach, T R Eykyn
Cancer cells undergoing starvation- and treatment-induced autophagy were found to exhibit reduced intracellular lactate, reduced rates of steady-state lactate excretion and reduced real-time pyruvate-lactate exchange rates, indicating that glycolytic metabolism was altered in autophagic cells. In this chapter, we describe the technical details of the use of (1)H-magnetic resonance spectroscopy (MRS) to measure endogenous cellular concentrations of lactate and glucose in autophagic cells and tissues, how to measure the rate of steady-state lactate excretion and glucose uptake by (1)H-MRS in autophagic cells, and details of the real-time measurement of [1-(13)C] pyruvate to lactate exchange in autophagic cells by (13)C-MRS-DNP (dynamic nuclear polarization)...
2017: Methods in Enzymology
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
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
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
Michal Leskes, Gunwoo Kim, Tao Liu, Alison L Michan, Fabien Aussenac, Patrick Dorffer, Subhradip Paul, Clare P Grey
Forming a stable solid electrolyte interphase (SEI) is critical 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 to enhance 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 (13)C-enriched electrolyte solvents. Our results indicate that DNP enhances the signal of outer SEI layers, enabling detection of natural abundance (13)C spectra from this component of the SEI on reasonable time frames...
February 21, 2017: Journal of Physical Chemistry Letters
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
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.)
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
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
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
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