The polarization agent, AMUPol, effectively polarizes proteins in both lysed (dashed lines, light green open circles) and intact (solid lines, closed dark green circles) HEK293 cells. (A) DNP enhancement and (B) TB,on values from saturation recovery experiments are dependent upon the AMUPol concentration. Points indicate average and error bars indicate standard deviation of the measurements. (C) Fit of the TB,on data (open circles) for lysed cells containing 5 mM AMUPol to a mono-exponential equation (black dashed line) had a TB,on value of 1.9 seconds with a regression error (lower plot) of 1.5%. (D) Fit of the TB,on data (closed circles) for intact cells incubated with 30 mM AMUPol to a mono-exponential equation (black solid line) had a TB,on value of 2.3 seconds with a regression error (lower plot) of 3.9%. Analyses for additional biomass components are presented in Supplemental Figure 3.