Interaction of Oxygen Partial Pressure and Energy Metabolism with the Relaxation Rate of Inorganic Phosphate: A ³¹P NMR Study

Abstract

It is well known that oxygen molecules present in liquid or solid samples can shorten NMR spin-lattice relaxation times (T₁) of the nucleus under investigation. Several studies have shown large decrements of ¹H, ¹³C, and ¹⁹F relaxation times mediated by the O₂ molecule (Lees and Muller, 1961; Ohuchi et al., 1979; Fishman et al., 1989). The positions of the 3lp atoms in phosphate compounds are stereometrically similar to some ¹³C atoms in organic compounds, and thus an effect of oxygen on the ³¹P T₁ is expected. Recently, we have shown (Okunieff et al., 1988) that oxygen breathing can significantly reduce the T₁ of 31p in the inorganic phosphate molecule (Pi). The degree to which this change was mediated by the O₂ molecule compared to secondary enzymatic processes that are also augmented when 100% oxygen is inspired (Okunieff et al., 1989), however is unknown.

This work supported in part by NIH grants CA48096, RR00995, and CA13311, and by the American Cancer Society Career Development Award.