On the importance of exchangeable NH protons in creatine for the magnetic coupling of creatine methyl protons in skeletal muscle

The methyl protons of creatine in skeletal muscle exhibit a strong off-reso nance magnetization transfer effect. The mechanism of this process is unkno wn. We previously hypothesized that the exchangeable amide/amino protons of creatine might be involved. To test this the characteristics of the creati ne magnetization transfer effect were investigated in excised rat hindleg s keletal muscle that was equilibrated in either H2O or D2O solutions contain ing creatine. The efficiency of off-resonance magnetization transfer to the protons of mobile creatine in excised muscle was similar to that previousl y reported in intact muscle in vivo. Equilibrating the isolated muscle in D 2O solution had no effect on the magnetic coupling to the immobile protons. It is concluded that exchangeable protons play a negligible role in the ma gnetic coupling of creatine methyl protons in muscle. (C) 2001 Academic Pre ss.