Hyperpolarised organic phosphates as NMR reporters of compartmental pH

Organic phosphate metabolites contain functional groups with p K a values near the physiologic pH range, yielding pH-dependent 13 C chemical shift changes of adjacent quaternary carbon sites. When formed in defined cellular compartments from exogenous hyperpolarised 13 C substrates, metabolites can thus yield localised pH values and correlations of organelle pH and catalytic activity. When formed in defined cellular compartments from exogenous hyperpolarised 13 C substrates, metabolites yield correlations of compartmental pH and catalytic activity.