Comparative intermolecular cross‐relaxation studies of human hemoglobin in red blood cells and bovine serum albumin in solution

Intermolecular cross‐relaxation rate (CR) spectra [1/ T IS (HDO) or 1/ T IS (H 2 O) vs f 2 (ppm) profiles] for bovine serum albumin [BSA; molecular weight (MW), 66 kDa] solution, partially hydrolyzed BSA gel (BSA*gel) and packed human red blood cells (RBCs) with normal or unstable hemoglobin (Hb; MW, 65 kDa) were studied using f 2 irradiation ranging from – 100 to 100 ppm at γ H 2 /2π of 250 Hz. The CR spectra for BSA*gel (pD 4.01, 0.10  M NaCl, 4.83 and 14.39%) exhibited different features in the off‐resonance region (below – 2.00 and above 12.0 ppm) relative to that for BSA solution (pD 7.14, 0.10  M NaCl, 14.39%), indicating the association of BSA* molecules in the gel state. The CR spectrum for packed RBCs was compared with those for BSA*gel and BSA solution (14.39%) by correcting for differences in protein concentration. The corrected CR spectrum for packed normal RBCs in the off‐resonance region was similar to that for BSA solution, indicating that the physical characteristics of Hb in normal RBCs may be in a solution‐like state. Our results on normal RBCs were approximately consistent with the previously reported thermodynamic and hydrodynamic findings that Hb in RBCs and/or in concentrated solution seems to be in a suspension of hard scaled particles. Copyright © 2011 John Wiley & Sons, Ltd.