Steinhoff H J, Kramm B, Hess G, Owerdieck C, Redhardt A
Institut für Biophysik, Ruhr-Universität Bochum, Germany.
Biophys J. 1993 Oct;65(4):1486-95. doi: 10.1016/S0006-3495(93)81217-7.
The dynamic properties of water in the hydration shell of hemoglobin have been studied by means of dielectric permittivity measurements and nuclear magnetic resonance spectroscopy. The temperature behavior of the complex permittivity of hemoglobin solutions has been measured at 3.02, 3.98, 8.59, and 10.80 GHz. At a temperature of 298 K the average rotational correlation time tau of water within a hydration shell of 0.5-nm thickness is determined from the activation parameters to be 68 +/- 10 ps, which is 8-fold the corresponding value of bulk water. Solvent proton magnetic relaxation induced by electron-nuclear dipole interaction between hemoglobin bound nitroxide spin labels and water protons is used to determine the translational diffusion coefficient D(T) of the hydration water. The temperature dependent relaxation behavior for Lamor frequencies between 3 and 90 MHz yields an average value D(298K) = (5 +/- 2) x 10(-10)m2 s-1, which is about one-fifth of the corresponding value of bulk water. The decrease of the water mobility in the hydration shell compared to the bulk is mainly due to an enhanced activation enthalpy.
通过介电常数测量和核磁共振光谱法研究了血红蛋白水化层中水的动力学性质。在3.02、3.98、8.59和10.80吉赫兹频率下测量了血红蛋白溶液复介电常数的温度行为。在298K温度下，根据活化参数确定厚度为0.5纳米的水化层内水的平均旋转相关时间τ为68±10皮秒，这是本体水相应值的8倍。利用血红蛋白结合的氮氧化物自旋标记与水质子之间的电子-核偶极相互作用引起的溶剂质子磁弛豫来确定水化水的平移扩散系数D(T)。在3至90兆赫兹拉莫尔频率下，温度依赖的弛豫行为得出平均值D(298K)=(5±2)×10⁻¹⁰平方米每秒，这约为本体水相应值的五分之一。与本体相比，水化层中水迁移率的降低主要是由于活化焓增加。
