Current NMR Strategies for Biomarker Discovery - Proteomic and Metabolomic Approaches to Biomarker Discovery - page 98

FIGURE 3 Schematic of 13 C labeling
of cerebral metabolites from labeled
glucose and acetate. (A) Metabolism of
[U- 13 C 6 ]-glucose via glutamatergic
and GABAergic TCA cycle labels
a -ketoglutarate 4,5 ( a -KG), hence, label-
ing of Glu 4,5 , which labels GABA 1,2 in
GABAergic neurons. 13 C labeling of
Gln 4,5 occurs from Glu 4,5 and GABA 1,2
via glutamate e glutamine and GABA e
glutamine cycle. (B) [2- 13 C]-acetate is
selectively transported in astroglia and
metabolized, thereby labels Gln 4 by
combined action of astroglial TCAcycle
and glutamine synthetase. Neuro-
transmitters Glu 4 and GABA 2 are
labeled from Gln 4 via glutamate e
glutamine and GABA e glutamine
substrates cycling between astroglia
and neurons, respectively. (Reprinted
from reference #120. Copyright 2012, with
permission from Elsevier.)

analysis include the 1 H- 13 C J-resolved HSQC
and 2D 1 H- 1 H TOCSY. 122,123 The 2D J-resolved
HSQC gives an identical multiplet pattern for
a wide range of isotopomer mixtures, and its
higher sensitivity compared to direct carbon
detection makes it more applicable for studies
in which sample size is limited. In the 2D
1 H- 1 H TOCSY, isotopomer information is
obtained from the 13 C satellite peaks.

HIGH-RESOLUTION MAGIC ANGLE
SPINNING (HR-MAS) NMR
SPECTROSCOPY

Magic angle spinning (MAS) has been
routinely employed for solid-state NMR spec-
troscopy. At the magic angle, 54.7 , broadening
effects from slow or restricted molecular
motion (dipolar interactions and chemical shift