Resolution of creatine and phosphocreatine1H signals in isolated human skeletal muscle using HR-MAS1H NMR

Proton nuclear magnetic resonance (NMR) spectra of freshly isolated human skeletal muscle samples contain creatine and phosphocreatine resonances with distinct chemical shifts that are easily visualized with magic angle spinning (MAS, spinning the sample rapidly at 54.7° with respect to the magnetic field) methods. The identification of the phosphocreatine resonance was based on two findings that: 1. the possible small dipolar coupling does not contribute to line splitting under rapid MAS, and 2. the 1H signal decreases concurrently with the phosphocreatine resonance observed in 31P NMR experiments. In the MAS 1H spectra the phosphocreatine resonance remains a singlet with a linewidth of less than 3 Hz. The creatine resonances are split into two peaks with linewidths at half height of approximately 2 and 6 Hz, respectively. The resonance with the broader linewidth represents creatine that is significantly motion-restricted and suggests that a creatine pool in muscle tissue is highly compartmentalized.