Fig. 1.
Phosphorus spectra acquired from vastus lateralis muscle during the saturation-transfer experiment. Selective γ-ATP saturation (arrow, right) is shown in green, with the control spectrum in blue. The control spectrum had selective saturation (arrow, left) at a downfield frequency equivalent to the frequency separation between γ-ATP and Pi. All other data acquisition parameters were the same in both conditions. The ratio of Pi magnetization with and without saturation (M′/M0) reflects the exchange of saturated spins from Pi to ATP and is used to calculate the unidirectional Pi→ATP flux.