Figure 1.

Representative ¹³C NMR spectrum of metabolites extracted from a fetal sheep heart right ventricle. Inset (1) shows ¹³C resonance of C-3 of glutamate along with line fitting carried out to estimate peak ratios. Inset (2) shows ¹³C resonance corresponding to C-4 of glutamate. Line fitting is not shown in inset (2) so as to not obscure the D34 doublet. In inset (1), “T” represents triplet arising from ¹³C label in carbons 2-3-4 of glutamate, “D” represents 2-3 and 3-4 isotopomers, and “S” arises ¹³C label in carbon-3 of glutamate in addition to natural abundance. In inset (2), “Q” represents quartet arising from ¹³C label in carbons 3-4-5 of glutamate; “D45”, doublet from 4-5 of glutamate; “D34”, doublet from 3-4 of glutamate; and “S” is singlet from ¹³C label in carbon-4 of glutamate in addition to natural abundance. ¹³C spectra acquisition parameters are detailed in Section 4.