Direct evidence from nuclear magnetic resonance studies for bound sodium in forg skeletal muscle.

The recent work of Cope on (23)Na magnetic resonance studies of frog muscle has been repeated with the view of investigating certain objections which can be raised concerning the original studies. The present work leads to the conclusion that Cope's results concerning bound sodium are essentially correct in that a large fraction of the (23)Na present does not contribute normally to a detectable nuclear magnetic resonance (NMR) signal. This "missing" signal can be detected at high radio-frequency intensity however, and a signal-saturation study distinctly reveals its presence.