Fig. 4: The T1-T2 correlational spectrum of blood microenvironment of (wild type) packed red blood cells.

There were in various physiological states; a oxygenated, b oxidized, and c deoxygenated states. The zoom-in details of decomposed relaxation reservoirs for fast relaxation components (S-peak and T-peak) and the slow relaxation component (bulk water molecules, R-peak) is not shown. The coordinate for R-peak is indicated at upper left of the spectrum. The coordinate is represented by (T2 relaxation (in ms), T1 relaxation (in ms), A-ratio). Freshly prepared oxy-Hb was subjected to oxidation with 10 mM sodium nitrite for 45 min, and sodium dithionite (in excess) for 40 min to chemically locked the Hb in the deoxygenated state. All the samples were washed thrice and resuspended into 1x PBS for micro MR measurements. The experimental parameters used were echo time = 200 µs, T1-incremental steps = 32 steps, and signal averaging = 4. The number of echoes used were 4000 (oxygenated Hb) and 2000 (oxidized Hb, deoxygenated Hb).