Doster W, Bachleitner A, Dunau R, Hiebl M, Lüscher E
Biophys J. 1986 Aug;50(2):213-9. doi: 10.1016/S0006-3495(86)83455-5.
The water of hydration in myoglobin crystals and solutions was studied at subzero temperatures by calorimetry and infrared spectroscopy (ir). For comparison we also investigated glycine, DL-alanine and DL-valine solutions. The hydration water remains amorphous at low temperatures. We find a broad glass transition between 180 and 270 K depending on the degree of hydration. The ice component shows a noncolligative melting point depression that is attributed to a finite conformational flexibility. The ir spectrum and the specific heat of water in myoglobin crystals was determined for the first time between 180 and 290 K. The glass transition in crystals is qualitatively similar to what is found in amorphous samples at the same water content. These data are compared with Mössbauer experiments and dielectric relaxation of water in myoglobin crystals. The similar temperature dependencies suggest a cross correlation between structural fluctuations and the thermal motion of crystal water. A hydrogen bond network model is proposed to explain these features. The essential ingredients are cooperativity and a distribution of hydrogen-bonded clusters.
通过量热法和红外光谱（ir）在零下温度下研究了肌红蛋白晶体和溶液中的水化水。为了进行比较，我们还研究了甘氨酸、DL-丙氨酸和DL-缬氨酸溶液。水化水在低温下保持无定形状态。我们发现根据水化程度，在180至270 K之间存在一个宽的玻璃化转变。冰成分显示出非依数性的熔点降低，这归因于有限的构象灵活性。首次测定了180至290 K之间肌红蛋白晶体中水的红外光谱和比热。晶体中的玻璃化转变在定性上与相同含水量的无定形样品中发现的情况相似。将这些数据与穆斯堡尔实验以及肌红蛋白晶体中水的介电弛豫进行了比较。相似的温度依赖性表明结构涨落与晶体水的热运动之间存在交叉相关性。提出了一个氢键网络模型来解释这些特征。其基本要素是协同性和氢键簇的分布。
