Figure 4.

Integrated intensities of laser-polarized ¹²⁹Xe NMR signals as a function of time for xenon dissolved in D₂O (■), with 1 mM apomyoglobin in D₂O (●), with 6 M deuterated urea in D₂O (▴), and with 1 mM apomyoglobin and 6 M urea-D₄ in D₂O (♦). Calculated spin-lattice relaxation times for ¹²⁹Xe in these solutions are 506 ± 5 s, 15.0 ± 0.3 s, 291 ± 2 s, and 59 ± 1 s, respectively. The inset shows the typical signal-to-noise with a single 3° pulse after the dissolution of laser-polarized xenon into a 1 mM solution of apomyoglobin; the shift is referenced to that in pure D₂O.