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Techniques in Solids NMR
• Magic Angle Spinning (MAS)
• High Power Decoupling
• Cross Polarization (CP)
• Assignment Strategies
• Structural Information
Dipole-Dipole Interaction are Large:
E = (0/4)(( 1· 2)/r3 – 3(1· r)( 2·r)/r
5)
r = i rx + j ry + k rz = i r sincos + j r sinsin + k r cos
1
2
r
B0
x y
z
r
First Order QM Term (Iz1Iz2 ) is most Important
A doublet results – much like scalar coupling but large:
60,000 Hz for a 13C-1H pair, 250,000 Hz for 1H-1H .
Splittings are angle dependent – ranging from
-60,000 to +30,000 for 13C-1H. All possibilities
superimpose: The result is a powder pattern
Points at 90º on a sphere
are most abundant
D
Other Anisotropies in NMR
H = HCSA + HD + HQ...
All share the following property:
Solution: < 3 cos 2 '– 1 > = 0
Solids: (3 cos 2 ' – 1) ≠ 0
CSA powder pattern
Magic Angle Spinning
• All interactions can be written in terms of Y20() = (3cos2()–1)/2
• Y20() can be transformed to another frame using Wigner Rotation
elements: Y20() = 2
m=-2 D2
m0(’’,’’) Y2m (’,’)
• D2m0(’’,’’) = (4/5) Y2
m (’’,’’)
• With rapid averaging over ’’, all terms except Y20(’’) go to zero
• Selecting ’’ = 54.7, all interactions, regardless of ’ value, are zero
• (3cos2()–1) = (3cos2(’)–1) <3cos2(54.7)–1> = 0
Dipolar couplings
CSA = 0
Quadrupolar couplings
Z
X Y
’
’’
’’
High power decoupling
• MAS only works if rate >> D
– Maximum rate ~50 kHz, typical 10kHz
– High speed rotors ~ 1mm diameter
• Decoupling helps
– Easy in solution 13C-1H J = ~125 Hz
– Solids 13C-1H J + D = ~60 kHz
• Solution is to do both
Cross Polarization Improves Sensitivity
selects for carbons with nearby protons
Magnetization transfer via dipolar coupling.
Hartman-Hahn:
gIBI = gSBS
Spinning Sidebands are Frequently Seen
When rotation rate is not >> anisotropies
Resonance position is modulated by rotation
Sidebands at the spinning frequency are produced
There are tricks that remove these:
TOSS – Total Suppression of Spinning Sidebands
180º pulses during rotor cycle dephases sideband
magnetization but preserves center band magnetization
2D spectra use a variety of connectivities
here: proton driven spin diffusion
Aliphatic region of the 13C,13C CP MAS PDSD of Zn-MMP-12 (16.4 T,
11.5 kHz MAS frequency, 15 ms mixing time). (Balayssac, Oschkinat, 2007)
(C) Backbone walk for the A21–A28 stretch of residues in LC8 using three-dimensional NUS-PACC NCACB and NCOCA
experiments. The total experiment times are 27 and 9 h for the NCACB and NCOCA experiments, respectively. Reproduced
with permission from ref 6. Copyright 2012 American Chemical Society.
Published in: Si Yan; Christopher L. Suiter; Guangjin Hou; Huilan Zhang; Tatyana Polenova; Acc. Chem. Res. 2013, 46, 2047-2058.
DOI: 10.1021/ar300309s
Copyright © 2013 American Chemical Society
Experiments can parallel solution assignment strategies
Getting Distance Information
REDOR (rotational echo double resonance) Gullion T, Schaefer J (1989) J Magn Reson 81:196
1H
15N
90x 180y
r r r r r r
180y……. 180y……
• Refocuses the effects of MAS on dipolar coupling
• Two 180 degree pulses every rotor period
• Get phase modulation due at magnitude of dipolar coupling
(A) 2D 13C–13C CORD sequences: (1) basic CORD; (2) CORDxix; (3) CORDxy4. These irradiation schemes are composites of
rotor-synchronized R2nv-symmetry sequences, R211 (ωrf = ωr), R212 (ωrf = ωr), R221 (ωrf = 1/2 ωr), and R222 (ωrf = 1/2 ωr).
Each R2nv element consists of two π pulses per n rotor periods. (B) 2D 13C–13C CORDxy4 spectra of U–13C,15N-LC8 (ωr =
40 kHz). Polarization transfer is uniformly efficient in both aliphatic and carbonyl regions of the spectrum.(11) Thioredoxin
Published in: Si Yan; Christopher L. Suiter; Guangjin Hou; Huilan Zhang; Tatyana Polenova; Acc. Chem. Res. 2013, 46, 2047-2058.
DOI: 10.1021/ar300309s
Copyright © 2013 American Chemical Society
Distances can be extracted using REDOR-like mixing
Angular dependence of dipolar interaction vectors
Separated local field spectra (PISEMA)
15N chemical shift
15N
– 1
H d
ipo
lar
co
up
ling
Gopinath, T.; Mote, KR.; Veglia, G (2013)
Sarcolipin in an oriented bicelle
Annual Reviews
2D solid-state NMR spectra of
uniformly 15N,13C-labeled Aβ1-40
amyloid fibrils. (a) 2D 13C-13C NMR
spectrum, obtained in a 14.1-T
magnetic field with 13.6-kHz
magic-angle spinning, using a
2.94-ms finite-pulse radio-
frequency-driven recoupling
(fpRFDR) sequence for spin
polarization transfer in the mixing
period. (b) 2D 15N-13C spectrum,
obtained with frequency-selective 15N-13C cross-polarization followed
by fpRFDR in the mixing period.
SOLIDS NMR REFERENCES
Opella, S.J. (2013) Structure Determination of Membrane Proteins by NMR
Spectroscopy Annual Rev. Anal. Chem, 6: 305-328.
Yan, S, Suiter, CL, Hou, G, Zhang, H and Polenova, T. (2013) Probing Structure and
Dynamics of Protein Assemblies by Magic Angle Spinning NMR Spectroscopy,
Accounts Chem. Research 46: 2047-2058.
Gopinath, T.; Mote, KR.; Veglia, G (2013) Sensitivity and resolution enhancement of
oriented solid-state NMR: Application to membrane proteins, Prog. NMR
Spectroscopy 75: 50-68.
Solid-state NMR of matrix metalloproteinase 12: An approach complementary to
solution NMR (2007) Balayssac S, Bertini I, Falber K, Oschkinat, H, et al.
CHEMBIOCHEM 8 486-489.
Solid-State NMR Studies of Amyloid Fibril Structure (2011) Tycko R. Ann. Rev. Phys.
Chem. 62, 279-299.
Recent contributions from solid-state NMR to membrane protein structure and
function, Judge, PJ and Watts, A, (2011) Cur. Opin. Chem. Biol. 15, 690-695.