Spin diffusion and the dynamic structure of a protein. Streptomyces subtilisin inhibitor

Saturation transfer in human red blood cells with normal and unstable hemoglobin

Saturation transfer phenomena from irradiated protein protons to observed water protons in packed human red blood cells (RBCs) with normal or unstable hemoglobin (Hb), i.e. Hb Yokohama and Hb Koeln, were studied using intermolecular cross-relaxation rates [CR; 1/T(IS)(H(2)O)], action spectra [[1-(I(infinity)/I(0))] vs f(2) (ppm), where I(0) and I(infinity) are the longitudinal magnetization of observed water protons before and after long-time f(2)-irradiation, respectively], CR spectra [CR vs f(2) (ppm)] and CR ratio vs f(2) (ppm) with f(2)-irradiation from -100 to 100 ppm at gammaH(2)/2pi of 69 or 250 Hz. RBCs (Hb Yokohama) exhibited many large Heinz bodies and strongly impaired filterability, while RBCs (Hb Koeln) showed few microscopically typical Heinz bodies and virtually normal filterability. However, increases in CR values for RBCs (Hb Koeln) and RBCs (Hb Yokohama), monitored by f(2)-irradiation below approximately -6 and above approximately 14 ppm, clearly indicated marked increases in association or aggregation of unstable Hb in RBCs compared with those in normal RBCs. CR values, monitored between approximately 0 and approximately 10 ppm, were related to not only association or aggregation of unstable Hb but also amounts of water in RBCs. Aggregation or association of unstable Hb exhibited greater effects on CR values compared with those of methemoglobin formation.

Basic studies on the equivalent cross-relaxation rate imaging (equivalent CRI)--phantom studies

We have studied saturation transfer in hydrophilic, cross-linked copolymer gels from irradiated polymer protons to observed water protons, using f2 (ppm) profiles of [1 - (I(infinity)/I(0))], [(I(0)/I(infinity)) - 1] or 1/T(IS)(H2O), where I(0) and I(infinity) are the longitudinal magnetization of the observed water protons before and after long-time-f2-irradiation on polymer protons, respectively, and 1/T(IS)(H2O) is the cross-relaxation rate. (A) [1 - (I(infinity)/I(0))] (magnetization transfer ratio, MTR) was used in magnetic resonance imaging (MRI) as the MTR imaging. 1/T(IS)(H2O) (cross-relaxation rate) was used in the imaging of the magnetization transfer rate constant. This method was quite time-consuming compared with MTR imaging. However, f2 (ppm) profiles of [(I(0)/I(infinity)) - 1] correlated well with corresponding profiles of 1/T(IS)(H2O), because [(I(0)/I(infinity)) - 1] is equal to 1/[T(IS)(H2O)/T1(H2O)]. These results lead us to the conclusion that [(I(0)/I(infinity)) - 1] might be applicable to cross-relaxation rate (CR)-like imaging, i.e. equivalent CRI. (B) W (%) (dry weight) profiles of [(I(0)/I(infinity)) - 1] and 1/T(IS)(H2O), obtained by near-resonance f2-irradiation, seem to indicate participation of molecular rigidity and an amount of bound water. However, those values, monitored with off-resonance f2-irradiation, seem to be independent of monomer composition and to indicate mainly participation of rigidity, i.e. W (%) of copolymer gels.