C8953 NMR structural analysis seminar
COSY + NOESY
Jan Novotny
novotnyjan@mail.muni.cz
March 19, 2015
NOESY - theoretical background
Nuclear Overhauser Effect
► consequence of dipol-dipol interaction via space:
/X/yUg (3COS  0 — 1)
■DD OC
'is
relaxation of a perturbed spin modulates the population of close spins = cross-relaxation
'is
dAI2 dt
= ~Pl(Iz ~
°is = W2-W0
90 90 90
► correlates nuclei in the proximity of cca 5 A
► P: excitation of spins by tt/2 pulse
► E: evolution of magnetization during ^ =>* encoding of magnetization by its own frequency
M: 7r/2 pulse: rotation of transversal magnetization into z-axis =>* transfer of magnetization via cross-relaxation during tmix
► D: 7r/2 pulse =>* acquisition (t2) of signal whose amplitude is modulated by frequency of interacting spins
NOE vs. size of the molecule
Correlation time rc
the average time it takes the molecule to rotate through one radian rc =
=>* ratio of umoi and carrier frequency
uj0:
^oTc < 1 (small molecules)
► positive NOE (W2 > W0)
► slow relaxation =>> long mixing period
► in NOESY spectrum crosspeaks of opposite phase relative to diagonal ones
^oTc > 1 (large molecules)
negative NOE (W2 < W0) fast relaxation =>- shorter mixing period
► crosspeaks of the same phase as the diagonal
uqtc « 1 (cca 1 kDa)
► NOE^O
► no crosspeaks =>- Rotating frame nOE Spectroscopy (ROESY)
►
►
NOE
w2-w0
0.5
w0 + 2w, + w2
-0.5 -
-1 -
NOE
NOESY - Palmatine in DMSO-c/6
DQ-COSY- Eserine in DMSO-cfô
E
CL CL
to 5
5 4 ô2 - 1H (ppm)
NOESY 600ms -
Eserine in DMSO-ŕfô
NOESY 600ms - Eserine in DMSO-d6
DQ-COSY - Colchicine in DMSO-c/6
8 6 4
CL CL
CO
8-
H3CJ8.O 8 i
H3C-0   p   13 p
21     H3C H3C23
8
82 - 1H (ppm)
J_u_M
1
?! et I
NOESY 600ms - Colchicine in DMSO-c/6
8 6 4 2
E
Q. Q.
to
6 4 ô2 - 1H (ppm)
□ S1