Dynamics-Based Selective 2D 1H/1H Chemical Shift
Correlation Spectroscopy under Ultrafast MAS
Conditions
Rongchun Zhang and Ayyalusamy Ramamoorthy*
Biophysics and Department of Chemistry, University of Michigan, Ann Arbor, MI
48109-1055, USA
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FIG. S1. Simulated signal decay with varied proton chemical shift anisotropy. The duration of
12-pulse dipolar filter is 11R=183.33s. The dipolar filter strength was increased by increasing the
dipolar filter cycles, Ncycle, so the total dipolar filter time is 183.33*Ncycle (s). The simulations were
performed using SIMPSON [1]. The spin system for simulations consisted of 3 protons, where the
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H-1H dipolar coupling was 12 kHz for each pair of protons. The isotropic chemical shift and
asymmetry parameter were set to zero for each spin, whereas the anisotropy chemical shift (the
difference between the least shielded component and the isotropic chemical shift) was set to be the
same for all spins, and varied from 0 to 15 ppm.
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FIG. S2. Simulated signal decay with increasing dipolar filter strength. The duration of 12-pulse
dipolar filter is 11R=183.33s. The dipolar filter strength was increased by increasing the dipolar filter
cycles, Ncycle, so the total dipolar filter time is equal to 183.33*Ncycle (s). The simulation was
performed with SIMPSON [1]. The spin system included 4 protons of alanine (positions according to
the alanine crystal structure with three protons close to N while one proton close to the alpha Carbon
atom.). Only proton-proton dipolar couplings are considered in the simulation. To include the effect of
rotation in the NH3+ group, the 1H-1H dipolar coupling for each pair of protons was set as one third of
its rigid limit value (~ 35.8 kHz). The vertical dashed and dotted lines indicates the dipolar filter time
when the signal intensity decays to 50% and 25% of the unfiltered signal intensity, respectively.
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FIG. S3. Experimental results obtained using the Hahn spin-echo () (a) and dipolar
filter (Figure 1A) (b) on collagen powder sample under 60 kHz MAS. Main signals from rigid
components are indicated by the red arrow. In the Hahn echo experiments, the dephasing time is equal
to , which is rotor-synchronized. In the dipolar filter experiments, the dipolar filter time was set at
n*R*Ncycle, and the dipolar filter time is increased by increasing Ncycle while keeping n=11.
Obviously, the dipolar filter is better at retaining signals from mobile groups as compared to the
Hahn-echo sequence under the same dephasing time. Even after 11 ms dipolar filter time, the mobile
signals basically do not decay (~85% remaining), while in Hahn-echo the mobile signals lost much
after a 10 ms dephasing time (~68% remaining).
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FIG. S4.
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H MAS NMR spectra of SBS with increasing dipolar filter strength (i.e., increasing the
value of Ncycle as indicated) when n=11. The arrow indicates signal from benzene protons, which is
zoomed in and shown in the bottom row.
FIG. S5.
Dipolar filter experimental results on collagen. (a) 1H MAS NMR spectra obtained from
a single pulse experiment (black) and the dipolar filter (Ncycle=50, n=11) experiment. (b) 2D 1H/1H
isotropic chemical shift correlation spectrum selectively observed for the mobile components of
collagen, with Ncycle=50. The fp-RFDR mixing time was 8 ms.
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FIG. S6.
Pulse sequences for 2D 1H/1H correlation experiments.
(a) 2D NOESY experiment
where the longitudinal magnetization transfer during the mixing time occurs due to NOE and/or spin
diffusion resulting from residual dipolar couplings under ultrafast MAS.
(b) 2D 1H/1H fp-RFDR
experiment where the longitudinal magnetization transfer happens mainly due to the spin diffusion
resulting from the recoupled proton-proton dipolar couplings.
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FIG. S7.
2D 1H/1H fp-RFDR (a) and NOESY (a) spectra obtained with a 8 ms mixing time. The
difference in the intensity of cross peaks clearly indicates the efficiency of fp-RFDR in recoupling
weak dipole-dipole couplings among protons in PB components.
References:
[1] M. Bak, J.T. Rasmussen, N.C. Nielsen, SIMPSON: A General Simulation Program for Solid-State NMR
Spectroscopy, Journal of Magnetic Resonance, 147 (2000) 296-330.
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