Transcript
The Physical Methods in Inorganic Chemistr
y
(Fall Term, 2004) (Fall Term, 2005) Department of Chemistry
National Sun Yat-sen University
無機物理方法（核磁共振部分）
Chapter 6
Nuclear Overhauser Effect (NOE) and NOESY
Population TransferIn population manipulations, the most commonly used technique is selective population transfer (SPT):
Nuclear Overhauser Effect (NOE)
N
SN
Sr
The distance between the two spins therefore can be determined by disturbing one of them and observing how other is affected.
Na23
electron
Nucleus-Electron OE: Mechanism
550
547
550
547
W2
W0
1000
995
100
99 =1+5=6
W2>>W0
999577
98520
=422+422=844
Nucleus-Electron OE: Mechanism
550
547
550
547
W2
W0
1000
995
100
99 =1+5=6
W2<<W0
580990
517107
=-410-410=-820
Nucleus-Nucleus OE (Nuclear OENOE): Mechanism
60
54
60
54
W2
W0
100
90
20
18 =2+10=12
W2>>W0
9058
2456
=32+32=64
Nucleus-Nucleus NOE: Mechanism
60
54
60
54
W2
W0
100
90
20
18 =2+10=12
W2<<W0
6490
5024
=-26-26=-52
Example: C-H NOE
Whenever a polarization or a transition of a spin is inverted or saturated, the polarization or transition of the other spins that are coupled to it will be affected.
Perturbation on a Spin (Saturation/Inversion) + Cross Relaxation
The Polarization of Another (Coupled) Spin Is Altered.
Depending on the relative magnitudes of W2 and W0, NOE factor can beLarger or smaller than 1 and can be both negative and positive.
w0 w2
Longitudinal Relaxation RatesAlso Affect NOE
)]2(6)(3)0([ 0016
,1 62
4220
JJJR
IIrII
60
54
60
54
W2
W0
100
90
20
18 =2+10=12
W2,W0, R1I, R1S all affect overall NOE.Here W2 > W0, R1I, R1S
9580
1934
=15+15=30
R1I
R1S
R1S
Positive NOE
Longitudinal Relaxation RatesAlso Affect NOE
)]2(6)(3)0([ 0016
,1 62
4220
JJJR
IIrII
60
54
60
54
W2
W0
100
90
20
18 =2+10=12
W2,W0, R1I, R1S all affect overall NOE.Here W2 > W0, R1I, but R1S>W2.
9690
1824
=6+6=12
R1I
R1S
R1S
No NOE
Longitudinal Relaxation RatesAlso Affect NOE
)]2(6)(3)0([ 0016
,1 62
4220
JJJR
IIrII
100
90
20
18 =2+10=12
W2,W0, R1I, R1S all affect overall NOE.Here W0> W2, but R1I>W0, R1S
9295
1922
=3-3=0!
60
54
60
54
W2
W0R1I
R1S
R1S
Negative NOE
)log( 0 c
logW
W2
W0
W1
-4 -3 -2 -1 0 1 2 3 4
Relaxation Rates and Motion
For slow motions,W0 is dominant and NOE tends tonegative.
Fast motion Slow motion
Homonuclear Steady State NOE
60
54
60
54
W2
W0
100
90
20
18 =2+10=12
NOE factor depends on W2, W0
9078
2436
=12+12=24
NOE Difference Spectrum(NOEdif)
Red: Saturated peakBlack: NOE affected peak
1D Homonuclear Transient NOE
A single spin is inverted and the spin system response isread using a 90° pulse after a “mixing” time delay of variable duration. In the transient mode, the NOE builds up due to cross-relaxation of nearby spins by the inverted spin as the entire spin system.
180o
100
9090
81
Neither have to be steadyNor have to be equilibrium
R1
R1
R1
90
81100
90
W2W0
98
8890
85
NOE: Essence
Whenever the polarization of one of two coupled spins deviates from its equilibrium value, the polarization of the other spin is affected by cross relaxations. The NOE factor (the extent that the polarization of the unperturbed spin is affected) depends on cross relaxation rates and longitudinal relaxation rates.
N
SN
Sr
A
B
When the distance between spins A and B is smaller than ~ 5 Å, NOE cross peaks are observable.
132
967 48510
1 25
3
4
6
7 8
910
1 25
3
4
67 8
910
132
967 48510
1D Homonucelar ROE
A single transition is inverted using a selective 180° pulse (along the x axis), and then a hard 90° x pulse is immediately applied to the spin system.This has the effect of placing the “inverted” magnetization along the -y axis while the rest of the magnetization is aligned along +y. Then, a low-power rectangular pulse is applied long the y-axis.This pulse is applied parallel to the magnetization (in the rotating frame) and effects no net rotation. Instead, it “locks” the magnetization along the y axis, and is referred to as a spin lock pulse. The magnetization is said to be spin locked becauseit doesn’t precess about B0, but the spins now precess aboutB1(the spin lock pulse). Therefore, under these conditions, the magnetization can be considered to being analogous to alignment along the z axis in the presence of B0 alone. Finally, the spins will relax towards a new equilibrium in the presence of B1; the characteristic time constant for this decay is called T1ρ forT1in the rotation frame.
180o90o
ROE Mechanism:All relaxation rates are changed
into rotating frame.
Rotating frame Note that both W2 and W0 promote ROE!
100
9090
81
98
9592
76Z
R1rho
R1rho
R1rho
90
90100
81
W2rho
W0,rho
Y
)]2(6)0([ 016 62
4220
JJ
IIr
NOEII
For homonuclear systems
)]2(3)0(2[ 016 62
4220
JJ
IIr
ROEII
Both W2 and W0 promote ROE
W2 promotes NOE while W0 blocks NOE
22152)(
c
cJ
I
NOEIS
IS
)]2(6)(3)0([ 0016
,1 62
4220
JJJR
IIrII
)]2(6)0([ 016 62
4220
JJ
IIr
NOEII
52
152
22)( c
c
cJ
cc
cJ
222 52
152)(
62
4220
12 II
c
r
ROEII
I
S
I
NOEIS
z
z
I
NOEIS
I
SIS
)0(
)0(
Some Applications of NOESY
Structure determination of biomacromolecules
Polymers
Sterochemistry
Hydration of biomolecules
)()cos()cos(
))sin()cos((
)sin()cos(
))sin()cos((
)sin()cos(
)()(
)erion transfmagnetizat(11
11
112
11
11
2
11
ZZSZIZ
SXSZ
IXIZ
SXSY
IXIYIt
YYZZ
SIatStI
tStS
tItI
tStS
tItI
SISI
m
X
Z
X
Sterochemistry
CORMA
Principle of CORMA
Example of CORMA
CORMA(COmplete Relaxation Matrix Analysis)
V(τm)=V0 exp(Rτm)
CORMA
NOESY of Poly(N-vinyl-carbazole): CHCl3, mixing time:450 ms, 500 MHz, 303 K
Detection of hydration water via observation of NOEs from water-protein --- G. Otting, E. Liepinsh, K. Wuthrich, Science 1991,254,974
BPTI 牛胰蛋白抑制劑
Residues : 58
Internal water : 4
Residence times:
Interior water:10-2-10-8s
Surface water:10-9s
Assignments of water-solute cross peak :
(a) Direct water-solute NOE
(hydration water-solute)
(b) Exchange-relayed NOE
(solute-solute)
(c) Chemical exchange
(bulk water-solute)
Non-labile
Labile
Labile
--- G. Otting, J. Progr. NMR. Spectrosc. 1997, 31 , 259
Glu1-190 ( mix=0.4 ms )
2
3
4
5
6
Significance to Structure Determination
rij=(1.78 Å)×(σkl/σij)1/6
Intensity:640Distance:1.78Å
Intensity:10Distance:3.56Å
A
B
C
D
E
F
C-terminal domain of rat Erp29 protein
C
R1
H
C
O
N
H
C
R2
H
C
O
N C C
R3
H H O
N
H
C
H
C
R4
O
N
H
C
H
C
R5
O
COSYNOESY NOESY
i i+1
i COSY NOESY (i+1) COSYNH-CαH iCαH-(i+1)NH
(i+1)NH-CαH
CTX II: 44-60
COSY
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