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/TIS(HDO) or 1/TIS(H2O) vs f2(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 f2 irradiation ranging from – 100 to 100 ppm at γH2/2π 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.