Multiple-quantum filtered ¹⁷O and ²³Na NMR analysis of mitochondrial suspensions

The fraction of strongly- and weakly-bound water molecules within mitochondrial suspensions, determined using three-quantum filtered ¹⁷O NMR relaxation analysis, was found to be large in comparison with that in erythrocytes and concentrated solutions of bovine serum albumen. It is suggested that bound water, together with regulation of mitochondrial matrix volume, may be an important controlling factor in the modulation of enzymic activity in the matrix. A spin I = 5/2 Jeener-Broekaert experiment and a four-quantum filtration experiment were used to demonstrate the absence of orientationally ordered water molecules within the mitochondrion. In contrast, the mitochondrial sodium environment was shown to be highly ordered using a spin I = 3/2 Jeener-Broekaert experiment.