Dynamic nuclear polarisation by thermal mixing: quantum theory and macroscopic simulations

Karabanov, Alexander; Kwiatkowski, Grzegorz; Perotto, Carlo U.; Wiśniewski, Daniel; McMaster, Jonathan; Lesanovsky, Igor; Köckenberger, Walter

doi:10.1039/c6cp04345c

Cited by 26 publications

(43 citation statements)

References 33 publications

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“…The dispersion parameter plays an important role of breaking the symmetry in the Hamiltonian by shifting one electron spin frequency with respect to the other, as was previously discussed for regular TM mechanism 18 . When the dispersion parameter = 0, the effective spin system Hamiltonian shown in eqns (7)(8)( 9) is symmetric with respect to swapping 1 and 2 operators, making the two electron spins indistinguishable.…”

Section: Quantum Mechanical Model Of Heteronuclear Dnpmentioning

confidence: 90%

“…Therefore, thermodynamically speaking, the two types of nuclei are in the indirect thermal contact with one another, leading to an observable polarization exchange between the two 11,16 . Recently, however, thermal mixing was also treated using models based on density matrix formalism 17,18 . In particular, the emergence of a common spin temperature in the dipolar reservoir of strongly coupled electron spins has been confirmed by the simulations 17 , which provides support for this concept, crucial to the thermodynamic description of TM-mechanism.…”

Section: Introductionmentioning

confidence: 99%

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Heteronuclear DNP of ¹H and ¹⁹F nuclei using BDPA as a polarizing agent

Gennaro

Karabanov

Потапов

et al. 2020

Phys. Chem. Chem. Phys.

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Section: Quantum Mechanical Model Of Heteronuclear Dnpmentioning

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Heteronuclear DNP of ¹H and ¹⁹F nuclei using BDPA as a polarizing agent

Gennaro

Karabanov

Потапов

et al. 2020

Phys. Chem. Chem. Phys.

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“…Depending on the degree of order and symmetries within the sample structure, D kk and D kk can either be well defined (e.g., for crystals) or considered to be random (e.g., for glasses). In amorphous materials ∆ k are also distributed due to the anisotropic interaction of the electrons with the static field, leading to inhomogeneous broadening of the EPR line [3,13,24]. Dissipative processes within the electron system are 1. (a) Steady-state polarization spectrapz(∆) obtained by the mean-field formula (6) (solid lines) and the numerically exact solution (dashed lines) for N = 4, D = 10 MHz, R2 = 10 6 s −1 and different temperature and microwave parameters: p = 0.11, ω1 = 75 kHz, R1 = 10 3 s −1 (red); p = 0.55, ω1 = 12 kHz, R1 = 10 s −1 (green); p = 0.99, ω1 = 7 kHz, R1 = 1 s −1 (blue).…”

mentioning

confidence: 99%

“…Insight into the dynamics of strongly coupled, microwave driven electronic ensembles is also needed in order to improve our understanding of dynamic nuclear polarization (DNP), which is an out-of-equilibrium technique to enhance the sensitivity of nuclear magnetic resonance (NMR) applications by orders of magnitude (see, e.g., Ref. [4][5][6]) -in particular, this concerns the cross effect and thermal mixing DNP mechanisms [7][8][9][10][11][12][13].…”

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confidence: 99%

Phase Transitions in Electron Spin Resonance Under Continuous Microwave Driving

et al. 2017

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We study an ensemble of strongly coupled electrons under continuous microwave irradiation interacting with a dissipative environment, a problem of relevance to the creation of highly polarized nonequilibrium states in nuclear magnetic resonance. We analyze the stationary states of the dynamics, described within a Lindblad master equation framework, at the mean-field approximation level. This approach allows us to identify steady-state phase transitions between phases of high and low polarization controlled by the distribution of disordered electronic interactions. We compare the mean-field predictions to numerically exact simulations of small systems and find good agreement. Our study highlights the possibility of observing collective phenomena, such as metastable states, phase transitions, and critical behavior, in appropriately designed paramagnetic systems. These phenomena occur in a low-temperature regime which is not theoretically tractable by conventional methods, e.g., the spin-temperature approach.

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“…Guarin et al characterized the TM-DNP using the nitroxide radicals at 3.5 T144 and Jähning et al investigated the TM in different nitroxide radical concentration at 3.5 T and 7 T 145 . Karabanov and coworkers described the quantum mechanics of TM-DNP and predicted that the strong asymmetry in the e-e coupling is essential for the efficient TM based polarization transfer 146. Kundu and coworkers further suggested that electron-electron double resonance (ELDOR) can be employed to identify the TM-DNP mechanism and differentiate between the CE and the TM 147.…”

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confidence: 99%

Probing the photointermediates of light-driven sodium ion pump KR2 by DNP-enhanced solid-state NMR

Jakdetchai¹

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KR2 is a light-driven sodium ion pump found in marine flavobacterium Krokinobacter Eikastus. The protein belongs to the microbial rhodopsin family, which is characterized by seven transmembrane helices and a retinal cofactor covalently bound to a conserved lysine residue through a Schiff base linkage. Specific features of KR2 and other sodium pumping rhodopsins are the NDQ motif, the N-terminal helix capping the protein at the extracellular side, and the sodium ion bound at the protomer interface in the pentameric structure. The ability to pump sodium ions was a surprising discovery since the positive charge at the Schiff base was long thought to hinder the transport of non-proton cations and the Grotthuss mechanism could not be applied to explain the Na+ transport. The photocycle of KR2 revealed by flashed photolysis and ultrafast femtosecond absorption spectroscopy consists of consecutive intermediates, named K, L, M, and O. Here, DNP-enhanced ssNMR was used to analyze various aspects of these intermediate states. The K/L-state can be generated and trapped by in-situ illumination inside the magnet at 110 K. The trapping of L-state together with the K-state at this temperature is unexpected as this usually leads to the trapping of only K-state in bacteriorhodopsin (BR), proteorhodopsin (PR), and channelrhodopsin 2 (ChR2). This observation suggests a lower energy barrier between K- and L-state in KR2. For the O-state, the intermediate was generated by illuminating outside the magnet, followed by rapid freezing in liquid nitrogen and transfer to the magnet. Based on these procedures, the retinal conformation, and the electrostatic environment at the Schiff base in KR2 dark, K-, L- and O-intermediates were probed using 13C-labeled retinals bound to 15N-labeled KR2 by both 1D and 2D magic angle spinning (MAS) NMR experiments. The obtained data show an all-trans retinal conformation with the distortion of 150° at H-C14-C15-H in the dark state whereas the retinal has a 13-cis, 15-anti conformation in the K- and L-state after light activation. Differences between K- and L-intermediates were observed. The retinal chemical shifts of the K-state show a large deviation from the model compound behavior between the middle and end part of the polyene chain. In the L-state, these differences are much less pronounced. These observations indicate that the light energy stored in the K-state dissipates into the protein in the subsequent photointermediate states. Furthermore, an additional shielding observed for C14 in L-state indicates the slight rotation toward a more compact 13-cis, 15-syn conformation. The distortion of the H-C14-C15-H angle in the L-state (136°) is larger than in the dark state. This twist of the retinal in the L-state would play an important role in lowering the pKa of the Schiff base, which is a prerequisite for the proton transfer from the Schiff base to the proton acceptor (D116). The electrostatic environments at the Schiff base in K- and L-states cause a de-shielding of the 15N nitrogen compared to the dark state. This indicates a stepwise stronger interaction with the counterion as the Schiff base proton moves away from the Schiff base and comes closer to the D116 in the transition from K- to L-state and approaches the proton transfer step during the M-state formation. In the O-state, the retinal was found to be in the all-trans conformation but differed to the dark state in the C13, C20, and Schiff base nitrogen chemical shifts. The largest effect (9 ppm) was observed for the Schiff base nitrogen, which could be explained by the effect of the positive charge of bound Na+ near the Schiff base in the O-state, coordinated by N112 and D116 as observed in the O-state crystal structure in the pentameric form. The structural change at the opsin followed the retinal isomerization and the energy transfer from the chromophore to the surrounding were also investigated in this thesis using various amino acids labeling schemes. Moreover, 1H-13C hNOE in combination with CE-DNP was applied to probe the dynamics of retinylidene methyl groups and 23Na MAS NMR was employed to detect the bound sodium ion at the protomer interface in KR2 dark state.

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Dynamic nuclear polarisation by thermal mixing: quantum theory and macroscopic simulations

Cited by 26 publications

References 33 publications

Heteronuclear DNP of ¹H and ¹⁹F nuclei using BDPA as a polarizing agent

Heteronuclear DNP of ¹H and ¹⁹F nuclei using BDPA as a polarizing agent

Phase Transitions in Electron Spin Resonance Under Continuous Microwave Driving

Probing the photointermediates of light-driven sodium ion pump KR2 by DNP-enhanced solid-state NMR

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Dynamic nuclear polarisation by thermal mixing: quantum theory and macroscopic simulations

Cited by 26 publications

References 33 publications

Heteronuclear DNP of 1H and 19F nuclei using BDPA as a polarizing agent

Heteronuclear DNP of 1H and 19F nuclei using BDPA as a polarizing agent

Phase Transitions in Electron Spin Resonance Under Continuous Microwave Driving

Probing the photointermediates of light-driven sodium ion pump KR2 by DNP-enhanced solid-state NMR

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Product

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Heteronuclear DNP of ¹H and ¹⁹F nuclei using BDPA as a polarizing agent

Heteronuclear DNP of ¹H and ¹⁹F nuclei using BDPA as a polarizing agent