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Dynamic nuclear polarization

Hyeonglim Seo, Ikjang Choi, Nicholas Whiting, Jingzhe Hu, Quy Son Luu, Shivanand Pudakalakatti, Caitlin McCowan, Yaewon Kim, Niki Zacharias, Seunghyun Lee, Pratip Bhattacharya, Youngbok Lee
Porous silicon nanoparticles have recently garnered attention as potentially-promising biomedical platforms for drug delivery and medical diagnostics. Here, we demonstrate porous silicon nanoparticles as contrast agents for ²⁹Si magnetic resonance imaging. Size-controlled porous silicon nanoparticles were synthesized by magnesiothermic reduction of silica nanoparticles and were surface activated for further functionalization. Particles were hyperpolarized via dynamic nuclear polarization to enhance their ²⁹Si MR signals; the particles demonstrated long ²⁹Si spin-lattice relaxation (T₁) times (~ 25 mins), which suggests potential applicability for medical imaging...
May 20, 2018: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
Ilia Kaminker, Songi Han
Dynamic nuclear polarization (DNP) takes center stage in nuclear magnetic resonance (NMR) as a tool to amplify its signal by orders of magnitude through the transfer of polarization from electron to nuclear spins. In contrast to modern NMR and electron paramagnetic resonance (EPR) that extensively rely on pulses for spin manipulation in the time domain, the current mainstream DNP technology exclusively relies on monochromatic continuous wave (CW) irradiation. This study introduces arbitrary phase shaped pulses that constitute a train of coherent chirp pulses in the time domain at 200 GHz (7 Tesla) to dramatically enhance the saturation bandwidth and DNP performance compared to CW DNP, yielding up to 500-fold in NMR signal enhancements...
May 18, 2018: Journal of Physical Chemistry Letters
Tanmoy Chakrabrty, Nir Goldin, Akiva Feintuch, Lothar Houben, Michal Leskes
Dynamic nuclear polarization (DNP), a technique in which the high electron spin polarization is transferred to surrounding nuclei via microwaves irradiation, equips solid state NMR spectroscopy with unprecedented sensitivity. The most commonly used polarization agents for DNP are nitroxide radicals. However, their applicability to inorganic materials is mostly limited to surface detection. Paramagnetic metal ions were recently introduced as alternatives for nitroxides. Doping inorganic solids with paramagnetic ions can be used to tune material properties and introduces endogenous DNP agents that can potentially provide sensitivity in the particles' bulk and surface...
May 17, 2018: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
Katia Le Barbu-Debus, Arne Scherrer, Aude Bouchet, Daniel Sebastiani, Rodolphe Vuilleumier, Anne Zehnacker
The influence of flexibility and hydrogen bond formation on the IR absorption and vibrational circular dichroism (VCD) spectrum of a floppy protic molecule, namely, (S)-1-indanol, is studied in both non-polar CCl4 and polar DMSO solvents. The experimental IR absorption and VCD spectra obtained by Fourier transform spectroscopy are interpreted using both static density functional theory (DFT) calculations and first principles molecular dynamics (FPMD) within DFT, using the nuclear velocity perturbation theory (NVPT)...
May 17, 2018: Physical Chemistry Chemical Physics: PCCP
E A Zhukov, E Kirstein, N E Kopteva, F Heisterkamp, I A Yugova, V L Korenev, D R Yakovlev, A Pawlis, M Bayer, A Greilich
The coherent spin dynamics of fluorine donor-bound electrons in ZnSe induced by pulsed optical excitation is studied in a perpendicular applied magnetic field. The Larmor precession frequency serves as a measure for the total magnetic field exerted onto the electron spins and, surprisingly, does not increase linearly with the applied field, but shows a step-like behavior with pronounced plateaus, given by multiples of the laser repetition rate. This discretization occurs by a feedback mechanism in which the electron spins polarize the nuclear spins, which in turn generate a local Overhauser field adjusting the total magnetic field accordingly...
May 16, 2018: Nature Communications
Thach Van Can, Johannes E McKay, Ralph T Weber, Chen Yang, Thierry Dubroca, Johan Van Tol, Stephen Hill, Robert G Griffin
We investigate a new time domain approach to dynamic nuclear polarization (DNP), the frequency-swept integrated solid effect (FS-ISE), utilizing a high power, broadband 94 GHz (3.35 T) pulse EPR spectrometer. The bandwidth of the spectrometer enabled measurement of the DNP Zeeman frequency/field profile that revealed two dominant polarization mechanisms, the expected ISE, and a new mechanism the stretched solid effect (S2E). At 94 GHz, despite the limitations in the microwave chirp pulse length (10 μs) and the repetition rate (2 kHz), we obtained signal enhancements up ~70 for the S2E and ~50 for the ISE...
May 14, 2018: Journal of Physical Chemistry Letters
An T Ta, Govind A Hegde, Brian D Etz, Anna G Baldwin, Yuan Yang, Jenifer C Shafer, Mark Peter Jensen, C Mark Maupin, Shubham Vyas
Actinide-Lanthanide Separation (ALSEP) has been a topic of interest in recent years as it has been shown to selectively extract problematic metals from spent nuclear fuel. However, the process suffers from slow kinetics prohibiting it from being applied to nuclear facilities. In effort to improve the process, many fundamental studies have been performed, but the majority have only focused on the thermodynamics of separation. Therefore, to understand the mechanism behind the ALSEP process, molecular dynamics (MD) simulations were utilized to obtain the dynamics and solvation characteristics for an organic extractant, 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (HEHEHP)...
May 14, 2018: Journal of Physical Chemistry. B
Michel Geiger, Anil Jagtap, Monu Kaushik, Han Sun, Daniel Stöppler, Snorri Sigurdsson, Björn Corzilius, Hartmut Oschkinat
Nitroxide biradicals are very efficient polarizing agents in magic angle spinning (MAS) cross effect (CE) dynamic nuclear polarization (DNP) nuclear magnetic resonance (NMR). Many recently synthesized, new radicals show superior DNP-efficiency in organic solvents but suffer from insufficient solubility in water or glycerol/water for biological applications. We report DNP efficiencies for two new radicals, the particularly well-water soluble bcTol-M and cyolyl-TOTAPOL, and include a comparison with three known biradicals, TOTAPOL, bcTol, and AMUPol...
May 9, 2018: Chemistry: a European Journal
A Kortyna, D M B Lesko, D J Nesbitt
The combination of a pulsed supersonic slit-discharge source and single-mode difference frequency direct absorption infrared spectroscopy permit first high resolution infrared study of the iodomethyl (CH2 I) radical, with the CH2 I radical species generated in a slit jet Ne/He discharge and cooled to 16 K in the supersonic expansion. Dual laser beam detection and collisional collimation in the slit expansion yield sub-Doppler linewidths (60 MHz), an absolute frequency calibration of 13 MHz, and absorbance sensitivities within a factor of two of the shot-noise limit...
May 7, 2018: Journal of Chemical Physics
Yeongjoon Lee, Chulhee Kwak, Ki-Woong Jeong, Prasannavenkatesh Durai, Kyoung-Seok Ryu, Eun-Hee Kim, Chaejoon Cheong, Hee-Chul Ahn, Hak Jun Kim, Yangmee Kim
Cold shock proteins (Csps) are expressed at lower-than-optimum temperatures, and they function as RNA chaperones; however, no structural studies on psychrophilic Csps have been reported. Here, we aimed to investigate the structure and dynamics of the Csp of the psychrophile Colwellia psychrerythraea 34H, ( Cp-Csp). Although Cp-Csp shares sequence homology, common folding patterns, and motifs-including a five β-stranded barrel-with its thermophilic counterparts, its thermostability (37 °C) was markedly lower than those of other Csps...
May 8, 2018: Biochemistry
Farida Shagieva, Sebastian Zaiser, Philipp Neumann, Durga Bhaktavatsala Rao Dasari, Rainer J Stöhr, Andrej Denisenko, Rolf Reuter, Carlos Andres Meriles, Joerg Wrachtrup
The ability to optically initialize the electronic spin of the nitrogen-vacancy (NV) center in diamond has long been considered a valuable resource to enhance the polarization of neighboring nuclei, but efficient polarization transfer to spin species outside the diamond crystal has proven challenging. Here we demonstrate variable-magnetic-field, microwave-enabled cross-polarization from the NV electronic spin to protons in a model viscous fluid in contact with the diamond surface. Further, slight changes in the cross-relaxation rate as a function of the wait time between successive repetitions of the transfer protocol suggest slower molecular dynamics near the diamond surface compared to that in bulk...
May 2, 2018: Nano Letters
Cheng-Shi Jiang, Chun-Lin Zhuang, Kongkai Zhu, Juan Zhang, Luis Alexandre Muehlmann, João Paulo Figueiró Longo, Ricardo Bentes Azevedo, Wen Zhang, Ning Meng, Hua Zhang
A new Keap1-Nrf2 protein-protein interaction (PPI) inhibitor ZJ01 was identified from our compound library by fluorescence polarization assay, surface plasmon resonance, molecular docking and molecular dynamics simulation. ZJ01 could in vitro trigger Nrf2 nuclear translocation, subsequently resulting in increased mRNA levels of Nrf2 target genes HO-1 and NQO1. Meanwhile, ZJ01 suppressed LPS-induced production of ROS and the mRNA levels of pro-inflammatory cytokines TNF-α, IL-1β and IL-6 in H9c2 cardiac cells...
December 2018: Journal of Enzyme Inhibition and Medicinal Chemistry
Makoto Negoro, Akinori Kagawa, Kenichiro Tateishi, Yoshiki Tanaka, Tomohiro Yuasa, Keigo Takahashi, Masahiro Kitagawa
Dissolution dynamic nuclear polarization (DNP) has recently gained attention as a method to enhance the sensitivity of liquid NMR spectroscopy and MRI. Here, we demonstrate dissolution of the sample hyperpolarized by DNP using photoexcited triplet electrons in 0.38 T at room temperature. The achieved polarization of 0.8% is 6100 times as high as that at thermal equilibrium in the condition. The result is an important step for DNP using photoexcited triplet electrons to become widely used in chemical and biomedical research...
April 13, 2018: Journal of Physical Chemistry. A
Johannes J Wittmann, Michael Eckardt, Wolfgang Harneit, Björn Corzilius
Dynamic nuclear polarization (DNP) can be applied to enhance the sensitivity of solid-state NMR experiments by several orders of magnitude due to microwave-driven transfer of spin polarization from unpaired electrons to nuclei. While the underlying quantum mechanical aspects are sufficiently well understood on a microscopic level, the exact description of the large-scale spin dynamics, usually involving hundreds to thousands of nuclear spins per electron, is still lacking consensus. Generally, it is assumed that nuclear hyperpolarization can only be observed on nuclei which do not experience strong influence of the unpaired electrons and thus being significantly removed from the paramagnetic polarizing agents...
April 12, 2018: Physical Chemistry Chemical Physics: PCCP
Songling Ma, Jiwon Choi, Xuemei Jin, Hyun-Yi Kim, Ji-Hye Yun, Weontae Lee, Kang-Yell Choi, Kyoung Tai No
The Wnt/β-catenin signaling pathway plays a significant role in the control of osteoblastogenesis and bone formation. CXXC finger protein 5 (CXXC5) has been recently identified as a negative feedback regulator of osteoblast differentiation through a specific interaction with Dishevelled (Dvl) protein. It was reported that targeting the Dvl-CXXC5 interaction could be a novel anabolic therapeutic target for osteoporosis. In this study, complex structure of Dvl PDZ domain and CXXC5 peptide was simulated with molecular dynamics (MD)...
April 7, 2018: Journal of Computer-aided Molecular Design
Mengxiao Liu, Guannan Zhang, Nilkamal Mahanta, Youngbok Lee, Christian Hilty
Paramagnetic relaxation enhancement (PRE) conjoint with hyperpolarized NMR reveals structural information on the enzyme-product complex in an on-going metalloenzyme catalyzed reaction. Substrates of pseudouridine monophosphate glycosidase are hyperpolarized using the dynamic nuclear polarization (DNP) method. Time series of13 C NMR spectra are subsequently measured with the enzyme containing diamagnetic Mg2+ or paramagnetic Mn2+ ions in the active site. The differences of the signal evolution and line widths in the Mg2+ vs...
April 6, 2018: Journal of Physical Chemistry Letters
Dongyoung Yoon, Alexandros I Dimitriadis, Murari Soundararajan, Christian Caspers, Jeremy Genoud, Stefano Alberti, Emile de Rijk, Jean-Philippe Ansermet
Nuclear hyperpolarization in liquid state by dynamic nuclear polarization (DNP) has been of great interest because of its potential use in NMR spectroscopy of small samples of biological and chemical compounds in aqueous media. Liquid state DNP generally requires microwave resonators in order to generate an alternating magnetic field strong enough to saturate electron spins in the solution. As a consequence, the sample size is limited to dimensions of the order of the wavelength, and this restricts the sample volume to less than 100 nL for DNP at 9 T (~ 260 GHz)...
April 5, 2018: Analytical Chemistry
Alisa Leavesley, Christopher B Wilson, Mark Sherwin, Songi Han
A paramount feature of robust experimental methods is acquiring consistent data. However, in dynamic nuclear polarization (DNP), it has been observed that the DNP-induced NMR signal enhancement of nominally the same sample can vary between different experimental sessions. We investigated the impact of various freezing conditions on the DNP results for a standard sample, a 50/40/10 by volume d8-glycerol/D2O/H2O solution of 40 mM 4-amino TEMPO, and found that annealing the samples 10 K above the glass transition temperature (Tg) causes significant changes to the DNP profiles and enhancements compared to that in rapidly frozen samples...
April 5, 2018: Physical Chemistry Chemical Physics: PCCP
Frédéric Mentink-Vigier, Guinevere Mathies, Yangping Liu, Anne-Laure Barra, Marc A Caporini, Daniel Lee, Sabine Hediger, Robert G Griffin, Gaël De Paëpe
Dynamic nuclear polarization (DNP) has the potential to enhance the sensitivity of magic-angle spinning (MAS) NMR by many orders of magnitude and therefore to revolutionize atomic resolution structural analysis. Currently, the most widely used approach to DNP for studies of chemical, material, and biological systems involves the cross-effect (CE) mechanism, which relies on biradicals as polarizing agents. However, at high magnetic fields (≥5 T), the best biradicals used for CE MAS-DNP are still far from optimal, primarily because of the nuclear depolarization effects they induce...
December 1, 2017: Chemical Science
Jeremias C Zill, Zhihui He, Marcus Tank, Bryan H Ferlez, Daniel P Canniffe, Yigal Lahav, Peter Bellstedt, A Alia, Igor Schapiro, John H Golbeck, Donald A Bryant, Jörg Matysik
Photochemically induced dynamic nuclear polarization (photo-CIDNP) has been observed in the homodimeric, type-1 photochemical reaction centers (RCs) of the acidobacterium, Chloracidobacterium (Cab.) thermophilum, by15 N magic-angle spinning (MAS) solid-state NMR under continuous white-light illumination. Three light-induced emissive (negative) signals are detected. In the RCs of Cab. thermophilum, three types of (bacterio)chlorophylls have previously been identified: bacteriochlorophyll a (BChl a), chlorophyll a (Chl a), and Zn-bacteriochlorophyll a' (Zn-BChl a') (Tsukatani et al...
March 30, 2018: Photosynthesis Research
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