Chemistry Reference
In-Depth Information
Fig. 10 Two-dimensional
DNP-enhanced
2
H-DQ-
13
C
correlation spectrum of U-
[
2
H
7
,
13
C
5
]-proline recorded
at 90 K. Reproduced with
permission from [
63
]
MAS experiments, respectively, compared to the same type of experiments in fully
protonated SH3. The optimum perdeuteration is found to be approximately 50%
which results in the maximum enhancement of
~ 148 in a
13
C MAS NMR
spectrum obtained using a ZrO
2
rotor. Maly et al
.
[
63
] also showed that
perdeuteration of biological macromolecules for magic angle spinning solid-state
NMR spectroscopy can yield high- resolution
2
H-
13
C correlation spectra. They
demonstrated that the combination of sample deuteration and DNP yields resolved
2
H-
13
C correlation spectra with a signal enhancement
e
700 compared to
a spectrum recorded with microwaves off and otherwise identical conditions. The
DNP process is studied using several polarizing agents and the technique is applied
to obtain
2
H-
13
C correlation spectra of U-[
2
H,
13
C] proline (Fig.
10
). Therefore the
use of perdeuterated proteins in DNP-MAS NMR will open new possibilities in the
application of these techniques to difficult biological problems.
e
4.3 Magnetic Resonance Imaging
MRI is one of the most powerful in vivo diagnostic tools due to its superb spatial
resolution and the amount of information it allows one to obtain, including
anatomical and function information as well as flux, perfusion, and diffusion
studies. However, compared with other imaging techniques, MRI's major drawback
is its inherent low sensitivity, which has precluded its use as a routine tool in the
clinic. Recently, great advances have been achieved on the application of MRI
with the enormous sensitivity enhancement afforded by DNP (
10,000-fold) [
64
].
The strong signal enhancement attainable by DNP has allowed the detection of
heteronuclei in MRI, yielding high quality images with very high signal to noise
ratios in a few seconds. The applications of hyperpolarized probes to MRI range
from vascular imaging, interventional imaging, and perfusion studies to the
emerging and challenging field of molecular/metabolic imaging. In fact, the high
signal intensities achievable by using hyperpolarized molecules make it possible to
detect and image the metabolic products formed upon the administration of the
hyperpolarized agent in vivo and allow early diagnosis and assessment of diseases
in personalized medicine in a non-invasive manner [
64
].
>
