Biomedical Engineering Reference
In-Depth Information
Figure 2.6
Comparison of NCA and NCO signal intensity as a function of the
overall correlation time. (A) Simulation result at two different magnetic
fields (11.7 T, corresponding to proton frequency of 500 MHz,
continuous line, and 18.8 T: 800 MHz, broken line) (B) nCA and nCO
1D spectrum recorded for 2-
13
C
13
C-
12
C alternately labelled GB1. The
effective molecular weight was modelled by adding 20% glycerol and
lowering the temperature.
'stairway' assignment procedure. A C
a
-C
a
plane at the frequency of v (N
i
)
(Figure 2.7(B), cyan shadow and (C), cyan planes) will have four correlations
of coordinates (v(C
a
i21
); v(C
a
i21
)), (v(C
a
i21
); v(C
a
i
)), (v(C
a
i
); v(C
a
i21
)), and
(v(C
a
i
); v(C
a
i
)). Thus, C
a
i
is directly correlated to its predecessor, C
a
i21
. The
Figure 2.7
Coherences correlated by the 3D CANCA experiment. (A) Illustration of
the coherences correlated with C
a
i
. The nuclei involved are coloured in
red, and their scalar couplings are indicated by red arrows. (B) Signals
and correlations observed in each plane of the N (cyan shadow) or the C
a
(yellow box) dimensions. (C) Schematic representation of the 3D
CANCA spectrum. Each C
a
-C
a
plane (coloured in blue) has intra-
residue and sequential carbon correlations. Sequential connections are
also found in the nitrogen dimension (yellow plane). Thus the assignment
can be easily established by navigating between C
a
-C
a
planes up and
down the 'stairway' along the nitrogen dimension. Adapted from ref. 51.
