A sensitivity increase of two orders of magnitude in proton (1H) and carbon (13C) spins via dynamic nuclear polarization (DNP) has been accomplished recently using a compact benchtop DNP polarizer operating at 1 T and 77 K. However, the DNP mechanisms at play at such a low magnetic field and high operating temperature are still not fully elucidated. A deeper understanding of the dominant polarization transfer mechanisms between electrons and 1H and 13C spins under these benchtop conditions is, therefore, required if one wants to devise strategies to boost sensitivity further. In this study, we found that DNP is generally dominated by solid effect (two-spin and three-spin) for narrow electron paramagnetic resonance (EPR) line radicals (15 mM trityl OX063) and cross effect for broad EPR line radicals (50 mM TEMPOL). For both radicals, the dominant DNP mechanisms were investigated varying the microwave frequency and measuring the 1H and 13C DNP enhancement factors to obtain 1H and 13C DNP spectra. The impact of varying the microwave power on the 1H DNP buildup times and the 1H nuclear spin relaxation times were important as well to distinguish between solid effect and cross effect DNP. Finally, time-resolved electron saturation simulations under continuous microwave irradiation could replicate the experimental 1H and 13C DNP spectra at 1 T and 77 K for both radicals considering their electron relaxation properties. Only for trityl OX063, the 13C DNP spectra showed additional DNP maxima compared to the simulations. This has been attributed to methyl rotor induced 1H–13C heteronuclear cross relaxation in [1–13C] acetate present at 1 T and 77 K.
REFERENCES
1.
J.
Eills
, D.
Budker
, S.
Cavagnero
, E. Y.
Chekmenev
, S. J.
Elliott
, S.
Jannin
, A.
Lesage
, J.
Matysik
, T.
Meersmann
, T.
Prisner
, J. A.
Reimer
, H.
Yang
, and I. V.
Koptyug
, “Spin hyperpolarization in modern magnetic resonance
,” Chem. Rev.
123
(4
), 1417
–1551
(2023
).2.
A.
Abragam
and M.
Goldman
, “Principles of dynamic nuclear polarisation
,” Rep. Prog. Phys.
41
(3
), 395
–467
(1978
).3.
S. J.
Elliott
, Q.
Stern
, M.
Ceillier
, T.
El Daraï
, S. F.
Cousin
, O.
Cala
, and S.
Jannin
, “Practical dissolution dynamic nuclear polarization
,” Prog. Nucl. Magn. Reson. Spectrosc.
126–127
, 59
–100
(2021
).4.
R. W.
Adams
, J. A.
Aguilar
, K. D.
Atkinson
, M. J.
Cowley
, P. I. P.
Elliott
, S. B.
Duckett
, G. G. R.
Green
, I. G.
Khazal
, J.
López-Serrano
, and D. C.
Williamson
, “Reversible interactions with para-hydrogen enhance NMR sensitivity by polarization transfer
,” Science
323
(5922
), 1708
–1711
(2009
).5.
T. G.
Walker
and W.
Happer
, “Spin-exchange optical pumping of noble-gas nuclei
,” Rev. Mod. Phys.
69
(2
), 629
–642
(1997
).6.
R. A.
Green
, R. W.
Adams
, S. B.
Duckett
, R. E.
Mewis
, D. C.
Williamson
, and G. G. R.
Green
, “The theory and practice of hyperpolarization in magnetic resonance using parahydrogen
,” Prog. Nucl. Magn. Reson. Spectrosc.
67
, 1
–48
(2012
).7.
J. H.
Ardenkjær-Larsen
, B.
Fridlund
, A.
Gram
, G.
Hansson
, L.
Hansson
, M. H.
Lerche
, R.
Servin
, M.
Thaning
, and K.
Golman
, “Increase in signal-to-noise ratio of > 10,000 times in liquid-state NMR
,” Proc. Natl. Acad. Sci. U. S. A.
100
(18
), 10158
–10163
(2003
).8.
A.
Bornet
, M.
Maucourt
, C.
Deborde
, D.
Jacob
, J.
Milani
, B.
Vuichoud
, X.
Ji
, J.-N.
Dumez
, A.
Moing
, G.
Bodenhausen
, S.
Jannin
, and P.
Giraudeau
, “Highly repeatable dissolution dynamic nuclear polarization for heteronuclear NMR metabolomics
,” Anal. Chem.
88
(12
), 6179
–6183
(2016
).9.
P. J. M.
van Bentum
, M.
Sharma
, S. G. J.
van Meerten
, and A. P. M.
Kentgens
, “Solid effect DNP in a rapid-melt setup
,” J. Magn. Reson.
263
, 126
–135
(2016
).10.
C.-G.
Joo
, K.-N.
Hu
, J. A.
Bryant
, and R. G.
Griffin
, “In situ temperature jump high-frequency dynamic nuclear polarization experiments: Enhanced sensitivity in liquid-state NMR spectroscopy
,” J. Am. Chem. Soc.
128
(29
), 9428
–9432
(2006
).11.
C.
Bocquelet
, N.
Rougier
, H.-N.
Le
, L.
Veyre
, C.
Thieuleux
, R.
Melzi
, A.
Purea
, D.
Banks
, J. G.
Kempf
, Q.
Stern
, E.
Vaneeckhaute
, and S.
Jannin
, “Boosting 1H and 13C NMR signals by orders of magnitude on a bench
,” Sci. Adv.
10
(49
), eadq3780
(2024
).12.
S. G. J.
van Meerten
, G. E.
Janssen
, and A. P. M.
Kentgens
, “Rapid-melt DNP for multidimensional and heteronuclear high-field NMR experiments
,” J. Magn. Reson.
310
, 106656
(2020
).13.
E.
Vaneeckhaute
, C.
Bocquelet
, L.
Bellier
, H.-N.
Le
, N.
Rougier
, S. A.
Jegadeesan
, S.
Vinod-Kumar
, G.
Mathies
, L.
Veyre
, C.
Thieuleux
, R.
Melzi
, D.
Banks
, J.
Kempf
, Q.
Stern
, and S.
Jannin
, “Full optimization of dynamic nuclear polarization on a 1 tesla benchtop polarizer with hyperpolarizing solids
,” Phys. Chem. Chem. Phys.
26
(33
), 22049
–22061
(2024
).14.
D.
Gajan
, A.
Bornet
, B.
Vuichoud
, J.
Milani
, R.
Melzi
, H. A.
van Kalkeren
, L.
Veyre
, C.
Thieuleux
, M. P.
Conley
, W. R.
Grüning
, M.
Schwarzwälder
, A.
Lesage
, C.
Copéret
, G.
Bodenhausen
, L.
Emsley
, and S.
Jannin
, “Hybrid polarizing solids for pure hyperpolarized liquids through dissolution dynamic nuclear polarization
,” Proc. Natl. Acad. Sci. U. S. A.
111
(41
), 14693
–14697
(2014
).15.
M.
Cavaillès
, A.
Bornet
, X.
Jaurand
, B.
Vuichoud
, D.
Baudouin
, M.
Baudin
, L.
Veyre
, G.
Bodenhausen
, J.-N.
Dumez
, S.
Jannin
, C.
Copéret
, and C.
Thieuleux
, “Tailored microstructured hyperpolarizing matrices for optimal magnetic resonance imaging
,” Angew Chem., Int. Ed. Engl.
57
(25
), 7453
–7457
(2018
).16.
O. S.
Leifson
and C. D.
Jeffries
, “Dynamic polarization of nuclei by electron-nuclear dipolar coupling in crystals
,” Phys. Rev.
122
(6
), 1781
–1795
(1961
).17.
A. V.
Kessenikh
, V. I.
Lushchikov
, A. A.
Manenkov
, and Y. V.
Taran
, “Proton polarization in irradiated polyethylenes
,” Sov. Phys.-Solid State
5
(4), 641
–649
(1963
) (in English).18.
C. F.
Hwang
and D. A.
Hill
, “New effect in dynamic polarization
,” Phys. Rev. Lett.
18
(4
), 110
–112
(1967
).19.
R. A.
Wind
, J.
Trommel
, and J.
Smidt
, “Proton dynamic nuclear polarization in coal
,” Fuel
58
(12
), 900
–901
(1979
).20.
R. A.
Wind
, F. E.
Anthonio
, M. J.
Duijvestijn
, J.
Smidt
, J.
Trommel
, and G. M. C.
de Vette
, “Experimental setup for enhanced 13C NMR spectroscopy in solids using dynamic nuclear polarization
,” J. Magn. Reson.
52
(3
), 424
–434
(1983
).21.
S.
Jannin
, A.
Comment
, F.
Kurdzesau
, J. A.
Konter
, P.
Hautle
, B.
van den Brandt
, and J. J.
van der Klink
, “A 140 GHz prepolarizer for dissolution dynamic nuclear polarization
,” J. Chem. Phys.
128
(24
), 241102
(2008
).22.
T.
Maly
, G. T.
Debelouchina
, V. S.
Bajaj
, K.-N.
Hu
, C.-G.
Joo
, M. L.
Mak
Jurkauskas
–, J. R.
Sirigiri
, P. C. A.
van der Wel
, J.
Herzfeld
, R. J.
Temkin
, and R. G.
Griffin
, “Dynamic nuclear polarization at high magnetic fields
,” J. Chem. Phys.
128
(5
), 052211
(2008
).23.
S. A.
Walker
, D. T.
Edwards
, T. A.
Siaw
, B. D.
Armstrong
, and S.
Han
, “Temperature dependence of high field 13C dynamic nuclear polarization processes with trityl radicals below 35 Kelvin
,” Phys. Chem. Chem. Phys.
15
(36
), 15106
–15120
(2013
).24.
J. H.
Ardenkjær-Larsen
, S.
Bowen
, J. R.
Petersen
, O.
Rybalko
, M. S.
Vinding
, M.
Ullisch
, and N. C.
Nielsen
, “Cryogen-free dissolution dynamic nuclear polarization polarizer operating at 3.35 T, 6.70 T, and 10.1 T
,” Magn. Reson. Med.
81
(3
), 2184
–2194
(2019
).25.
R. G.
Griffin
, T. M.
Swager
, and R. J.
Temkin
, “High frequency dynamic nuclear polarization: New directions for the 21st century
,” J. Magn. Reson.
306
, 128
–133
(2019
).26.
P.
Berruyer
, S.
Björgvinsdóttir
, A.
Bertarello
, G.
Stevanato
, Y.
Rao
, G.
Karthikeyan
, G.
Casano
, O.
Ouari
, M.
Lelli
, C.
Reiter
, F.
Engelke
, and L.
Emsley
, “Dynamic nuclear polarization enhancement of 200 at 21.15 T enabled by 65 kHz magic angle spinning
,” J. Phys. Chem. Lett.
11
(19
), 8386
–8391
(2020
).27.
M.
Borghini
, “Spin-temperature model of nuclear dynamic polarization using free radicals
,” Phys. Rev. Lett.
20
(9
), 419
–421
(1968
).28.
W. T.
Wenckebach
, T. J. B.
Swanenburg
, and N. J.
Poulis
, “Thermodynamics of spin systems in paramagnetic crystals
,” Phys. Rep.
14
(5
), 181
–255
(1974
).29.
A. G.
Redfield
, “Nuclear magnetic resonance saturation and rotary saturation in solids
,” Phys. Rev.
98
(6
), 1787
–1809
(1955
).30.
N.
Bloembergen
, S.
Shapiro
, P. S.
Pershan
, and J. O.
Artman
, “Cross-relaxation in spin systems
,” Phys. Rev.
114
(2
), 445
–459
(1959
).31.
B. N.
Provotorov
, “A quantum-statistical theory of cross-relaxation
,” Sov. Phys. JETP
15
(3
), 611
–614
(1962
).32.
W. T.
Wenckeback
, G. M.
van den Heuvel
, H.
Hoogstraate
, T. J. B.
Swanenburg
, and N. J.
Poulis
, “Experimental proof of the strong coupling between the electron spin-spin reservoir and a nuclear spin system in dilute paramagnetic crystals
,” Phys. Rev. Lett.
22
(12
), 581
–583
(1969
).33.
V. A.
Atsarkin
and M. I.
Rodak
, “Temperature of spin-spin interactions in electron spin resonance
,” Sov. Phys. - Usp.
15
(3
), 251
(1972
).34.
W. T.
Wenckebach
, “Dynamic nuclear polarization via thermal mixing: Beyond the high temperature approximation
,” J. Magn. Reson.
277
, 68
–78
(2017
).35.
M.
Goldman
, Spin Temperature and Nuclear Magnetic Resonance in Solids
, The International Series of Monographs on Physics
(Clarendon Press
, 1970
).36.
R. A.
Wind
, M. J.
Duijvestijn
, C.
van der Lugt
, A.
Manenschijn
, and J.
Vriend
, “Applications of dynamic nuclear polarization in 13C NMR in solids
,” Prog. Nucl. Magn. Reson. Spectrosc.
17
, 33
–67
(1985
).37.
D.
Shimon
, Y.
Hovav
, A.
Feintuch
, D.
Goldfarb
, and S.
Vega
, “Dynamic nuclear polarization in the solid state: A transition between the cross effect and the solid effect
,” Phys. Chem. Chem. Phys.
14
(16
), 5729
–5743
(2012
).38.
Y.
Zhao
, H.
El Mkami
, R. I.
Hunter
, G.
Casano
, O.
Ouari
, and G. M.
Smith
, “Large cross-effect dynamic nuclear polarisation enhancements with kilowatt inverting chirped pulses at 94 GHz
,” Commun. Chem.
6
(1
), 171
(2023
).39.
A.
Equbal
, Y.
Li
, T.
Tabassum
, and S.
Han
, “Crossover from a solid effect to thermal mixing 1H dynamic nuclear polarization with trityl-OX063
,” J. Phys. Chem. Lett.
11
(9
), 3718
–3723
(2020
).40.
A.
Equbal
, A.
Leavesley
, S. K.
Jain
, and S.
Han
, “Cross-effect dynamic nuclear polarization explained: Polarization, depolarization, and oversaturation
,” J. Phys. Chem. Lett.
10
(3
), 548
–558
(2019
).41.
C. T.
Farrar
, D. A.
Hall
, G. J.
Gerfen
, S. J.
Inati
, and R. G.
Griffin
, “Mechanism of dynamic nuclear polarization in high magnetic fields
,” J. Chem. Phys.
114
(11
), 4922
–4933
(2001
).42.
K. O.
Tan
, M.
Mardini
, C.
Yang
, J. H.
Ardenkjær-Larsen
, and R. G.
Griffin
, “Three-spin solid effect and the spin diffusion barrier in amorphous solids
,” Sci. Adv.
5
(7
), eaax2743
(2019
).43.
Y.
Quan
, Y.
Ouyang
, M.
Mardini
, R. S.
Palani
, D.
Banks
, J.
Kempf
, W. T.
Wenckebach
, and R. G.
Griffin
, “Resonant mixing dynamic nuclear polarization
,” J. Phys. Chem. Lett.
14
(31
), 7007
–7013
(2023
).44.
K.
Kundu
, M. R.
Cohen
, A.
Feintuch
, D.
Goldfarb
, and S.
Vega
, “Experimental quantification of electron spectral-diffusion under static DNP conditions
,” Phys. Chem. Chem. Phys.
21
(1
), 478
–489
(2019
).45.
K.
Kundu
, A.
Feintuch
, and S.
Vega
, “Electron–electron cross-relaxation and spectral diffusion during dynamic nuclear polarization experiments on solids
,” J. Phys. Chem. Lett.
9
(7
), 1793
–1802
(2018
).46.
Y.
Hovav
, A.
Feintuch
, and S.
Vega
, “Theoretical aspects of dynamic nuclear polarization in the solid state – The cross effect
,” J. Magn. Reson.
214
, 29
–41
(2012
).47.
Y.
Hovav
, A.
Feintuch
, and S.
Vega
, “Theoretical aspects of dynamic nuclear polarization in the solid state – The solid effect
,” J. Magn. Reson.
207
(2
), 176
–189
(2010
).48.
D.
Shimon
, A.
Feintuch
, D.
Goldfarb
, and S.
Vega
, “Static 1H dynamic nuclear polarization with the biradical TOTAPOL: A transition between the solid effect and the cross effect
,” Phys. Chem. Chem. Phys.
16
(14
), 6687
–6699
(2014
).49.
W. T.
Wenckebach
, “Dynamic nuclear polarization via the cross effect and thermal mixing: A. The role of triple spin flips
,” J. Magn. Reson.
299
, 124
–134
(2019
).50.
W. T.
Wenckebach
, “Spectral diffusion of electron spin polarization in glasses doped with radicals for DNP
,” J. Magn. Reson.
360
, 107651
(2024
).51.
C. F.
Hwang
and D. A.
Hill
, “Phenomenological model for the new effect in dynamic polarization
,” Phys. Rev. Lett.
19
(18
), 1011
–1014
(1967
).52.
D. S.
Wollan
, “Dynamic nuclear polarization with an inhomogeneously broadened ESR line. I. Theory
,” Phys. Rev. B
13
(9
), 3671
–3685
(1976
).53.
Y.
Hovav
, I.
Kaminker
, D.
Shimon
, A.
Feintuch
, D.
Goldfarb
, and S.
Vega
, “The electron depolarization during dynamic nuclear polarization: Measurements and simulations
,” Phys. Chem. Chem. Phys.
17
(1
), 226
–244
(2015
).54.
F.
Bloch
, “Nuclear induction
,” Phys. Rev.
70
(7–8
), 460
–474
(1946
).55.
H. C.
Torrey
, “Bloch equations with diffusion terms
,” Phys. Rev.
104
(3
), 563
–565
(1956
).56.
B. N.
Provotorov
, “Magnetic resonance saturation in crystals
,” Sov. Phys. JETP
14
(5
), 1126
–1131
(1962
).57.
E. M. M.
Weber
, H.
Vezin
, J. G.
Kempf
, G.
Bodenhausen
, D.
Abergél
, and D.
Kurzbach
, “Anisotropic longitudinal electronic relaxation affects DNP at cryogenic temperatures
,” Phys. Chem. Chem. Phys.
19
(24
), 16087
–16094
(2017
).58.
E.
Vaneeckhaute
and S.
Jannin
(2025
). “Dynamic nuclear polarization mechanisms using TEMPOL and trityl OX063 radicals at 1 T and 77 K
,” Zenodo. https://doi.org/10.5281/zenodo.1504160959.
E.
Vaneeckhaute
and S.
Jannin
(2024
). “Dynamic nuclear polarization mechanisms using TEMPOL and trityl OX063 radicals at 1 T and 77 K
,” Zenodo. https://doi.org/10.5281/zenodo.1433896760.
G.
Mathies
, M. A.
Caporini
, V. K.
Michaelis
, Y.
Liu
, K.-N.
Hu
, D.
Mance
, J. L.
Zweier
, M.
Rosay
, M.
Baldus
, and R. G.
Griffin
, “Efficient dynamic nuclear polarization at 800 MHz/527 GHz with trityl-nitroxide biradicals
,” Angew. Chem., Int. Ed.
54
(40
), 11770
–11774
(2015
).61.
A.
Equbal
, K.
Tagami
, and S.
Han
, “Balancing dipolar and exchange coupling in biradicals to maximize cross effect dynamic nuclear polarization
,” Phys. Chem. Chem. Phys.
22
(24
), 13569
–13579
(2020
).62.
A. A.
Smith
, B.
Corzilius
, A. B.
Barnes
, T.
Maly
, and R. G.
Griffin
, “Solid effect dynamic nuclear polarization and polarization pathways
,” J. Chem. Phys.
136
(1
), 015101
(2012
).63.
W. T.
Wenckebach
, “The solid effect
,” Appl. Magn. Reson.
34
(3–4
), 227
(2008
).64.
K. O.
Tan
and R. G.
Griffin
, “Observation of a four-spin solid effect
,” J. Chem. Phys.
156
(17
), 174201
(2022
).65.
D.
Daube
, V.
Aladin
, J.
Heiliger
, J. J.
Wittmann
, D.
Barthelmes
, C.
Bengs
, H.
Schwalbe
, and B.
Corzilius
, “Heteronuclear cross-relaxation under solid-state dynamic nuclear polarization
,” J. Am. Chem. Soc.
138
(51
), 16572
–16575
(2016
).66.
K. J.
Donovan
, A.
Lupulescu
, and L.
Frydman
, “Heteronuclear cross-relaxation effects in the NMR spectroscopy of hyperpolarized targets
,” ChemPhysChem
15
(3
), 436
–443
(2014
).67.
R.
Shankar Palani
, M.
Mardini
, Y.
Quan
, and R. G.
Griffin
, “Dynamic nuclear polarization with trityl radicals
,” J. Magn. Reson.
349
, 107411
(2023
).68.
N. A.
Prisco
, A. C.
Pinon
, L.
Emsley
, and B. F.
Chmelka
, “Scaling analyses for hyperpolarization transfer across a spin-diffusion barrier and into bulk solid media
,” Phys. Chem. Chem. Phys.
23
(2
), 1006
–1020
(2021
).69.
W. E.
Blumberg
, “Nuclear spin-lattice relaxation caused by paramagnetic impurities
,” Phys. Rev.
119
(1
), 79
–84
(1960
).70.
K.
Kundu
, A.
Feintuch
, and S.
Vega
, “Theoretical aspects of the cross effect enhancement of nuclear polarization under static dynamic nuclear polarization conditions
,” J. Phys. Chem. Lett.
10
(8
), 1769
–1778
(2019
).71.
S.
Stoll
and A.
Schweiger
, “EasySpin, a comprehensive software package for spectral simulation and analysis in EPR
,” J. Magn. Reson.
178
(1
), 42
–55
(2006
).72.
L.
Lumata
, Z.
Kovacs
, A. D.
Sherry
, C.
Malloy
, S.
Hill
, J.
van Tol
, L.
Yu
, L.
Song
, and M. E.
Merritt
, “Electron spin resonance studies of trityl OX063 at a concentration optimal for DNP
,” Phys. Chem. Chem. Phys.
15
(24
), 9800
–9807
(2013
).73.
P.
Demay-Drouhard
, H. Y. V.
Ching
, C.
Decroos
, R.
Guillot
, Y.
Li
, L. C.
Tabares
, C.
Policar
, H. C.
Bertrand
, and S.
Un
, “Understanding the g-tensors of perchlorotriphenylmethyl and Finland-type trityl radicals
,” Phys. Chem. Chem. Phys.
22
(36
), 20792
–20800
(2020
).74.
J. R.
Biller
, V. M.
Meyer
, H.
Elajaili
, G. M.
Rosen
, S. S.
Eaton
, and G. R.
Eaton
, “Frequency dependence of electron spin relaxation times in aqueous solution for a nitronyl nitroxide radical and perdeuterated-tempone between 250 MHz and 34 GHz
,” J. Magn. Reson.
225
, 52
–57
(2012
).75.
J.-L.
Du
, G. R.
Eaton
, and S. S.
Eaton
, “Temperature and orientation dependence of electron-spin relaxation rates for bis(diethyldithiocarbamato)copper(II)
,” J. Magn. Reson., Ser. A
117
(1
), 67
–72
(1995
).76.
D.
Banerjee
, D.
Shimon
, A.
Feintuch
, S.
Vega
, and D.
Goldfarb
, “The interplay between the solid effect and the cross effect mechanisms in solid state 13C DNP at 95 GHz using trityl radicals
,” J. Magn. Reson.
230
, 212
–219
(2013
).77.
W. T.
Wenckebach
, Essentials of Dynamic Nuclear Polarization
(Spindrift Publications
, 2016
).78.
G.
Menzildjian
, J.
Schlagnitweit
, G.
Casano
, O.
Ouari
, D.
Gajan
, and A.
Lesage
, “Polarizing agents for efficient high field DNP solid-state NMR spectroscopy under magic-angle spinning: From design principles to formulation strategies
,” Chem. Sci.
14
(23
), 6120
–6148
(2023
).79.
V. K.
Michaelis
, A. A.
Smith
, B.
Corzilius
, O.
Haze
, T. M.
Swager
, and R. G.
Griffin
, “High-field 13C dynamic nuclear polarization with a radical mixture
,” J. Am. Chem. Soc.
135
(8
), 2935
–2938
(2013
).80.
D.
Shimon
, Y.
Hovav
, I.
Kaminker
, A.
Feintuch
, D.
Goldfarb
, and S.
Vega
, “Simultaneous DNP enhancements of 1H and 13C nuclei: Theory and experiments
,” Phys. Chem. Chem. Phys.
17
(17
), 11868
–11883
(2015
).81.
K.
Takegoshi
and T.
Terao
, “13C nuclear Overhauser polarization nuclear magnetic resonance in rotating solids: Replacement of cross polarization in uniformly 13C labeled molecules with methyl groups
,” J. Chem. Phys.
117
(4
), 1700
–1707
(2002
).82.
A. W.
Overhauser
, “Polarization of nuclei in metals
,” Phys. Rev.
92
(2
), 411
(1953
).83.
R.
Kaiser
, “Use of the nuclear Overhauser effect in the analysis of high-resolution nuclear magnetic resonance spectra
,” J. Chem. Phys.
39
(10
), 2435
–2442
(1963
).84.
V.
Copie
, A. E.
McDermott
, K.
Beshah
, J. C.
Williams
, M.
Spijker-Assink
, R.
Gebhard
, J.
Lugtenburg
, J.
Herzfeld
, and R. G.
Griffin
, “Deuterium solid-state nuclear magnetic resonance studies of methyl group dynamics in bacteriorhodopsin and retinal model compounds: Evidence for a 6-s-Trans chromophore in the protein
,” Biochemistry
33
(11
), 3280
–3286
(1994
).85.
J. L.
White
and P.
Mirau
, “Probing miscibility and intermolecular interactions in solid polymer blends using the nuclear overhauser effect
,” Macromolecules
26
(12
), 3049
–3054
(1993
).86.
J. L.
White
, “Exploiting methyl groups as motional labels for structure analysis in solid polymers
,” Solid State Nucl. Magn. Reson.
10
(1–2
), 79
–88
(1997
).87.
V.
Aladin
, M.
Vogel
, R.
Binder
, I.
Burghardt
, B.
Suess
, and B.
Corzilius
, “Complex formation of the tetracycline-binding aptamer investigated by specific cross-relaxation under DNP
,” Angew. Chem., Int. Ed.
58
(15
), 4863
–4868
(2019
).88.
V.
Aladin
and B.
Corzilius
, “Methyl dynamics in amino acids modulate heteronuclear cross relaxation in the solid state under MAS DNP
,” Solid State Nucl. Magn. Reson.
99
, 27
–35
(2019
).© 2025 Author(s). Published under an exclusive license by AIP Publishing.
2025
Author(s)
You do not currently have access to this content.
