Kiyosawa Keitaro
Division of Biophysical Engineering, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan.
Biophys Chem. 2003 May 1;104(1):171-88. doi: 10.1016/s0301-4622(02)00365-4.
For survival in adverse environments where there is drought, high salt concentration or low temperature, some plants seem to be able to synthesize biochemical compounds, including proteins, in response to changes in water activity or osmotic pressure. Measurement of the water activity or osmotic pressure of simple aqueous solutions has been based on freezing point depression or vapor pressure deficit. Measurement of the osmotic pressure of plants under water stress has been mainly based on vapor pressure deficit. However, differences have been noted for osmotic pressure values of aqueous polyethylene glycol (PEG) solutions measured by freezing point depression and vapor pressure deficit. For this paper, the physicochemical basis of freezing point depression and vapor pressure deficit were first examined theoretically and then, the osmotic pressure of aqueous ethylene glycol and of PEG solutions were measured by both freezing point depression and vapor pressure deficit in comparison with other aqueous solutions such as NaCl, KCl, CaCl(2), glucose, sucrose, raffinose, and bovine serum albumin (BSA) solutions. The results showed that: (1) freezing point depression and vapor pressure deficit share theoretically the same physicochemical basis; (2) theoretically, they are proportional to the molal concentration of the aqueous solutions to be measured; (3) in practice, the osmotic pressure levels of aqueous NaCl, KCl, CaCl(2), glucose, sucrose, and raffinose solutions increase in proportion to their molal concentrations and there is little inconsistency between those measured by freezing point depression and vapor pressure deficit; (4) the osmotic pressure levels of aqueous ethylene glycol and PEG solutions measured by freezing point depression differed from the values measured by vapor pressure deficit; (5) the osmotic pressure of aqueous BSA solution measured by freezing point depression differed slightly from that measured by vapor pressure deficit.
为了在干旱、高盐浓度或低温等恶劣环境中生存，一些植物似乎能够响应水分活度或渗透压的变化而合成包括蛋白质在内的生化化合物。简单水溶液的水分活度或渗透压的测量一直基于冰点降低或蒸气压亏缺。水分胁迫下植物渗透压的测量主要基于蒸气压亏缺。然而，通过冰点降低和蒸气压亏缺测量的聚乙二醇（PEG）水溶液的渗透压值存在差异。在本文中，首先从理论上研究了冰点降低和蒸气压亏缺的物理化学基础，然后，通过冰点降低和蒸气压亏缺测量了乙二醇水溶液和PEG水溶液的渗透压，并与其他水溶液如NaCl、KCl、CaCl₂、葡萄糖、蔗糖、棉子糖和牛血清白蛋白（BSA）溶液进行了比较。结果表明：（1）冰点降低和蒸气压亏缺在理论上具有相同的物理化学基础；（2）理论上，它们与待测水溶液的质量摩尔浓度成正比；（3）在实际中，NaCl、KCl、CaCl₂、葡萄糖、蔗糖和棉子糖水溶液的渗透压水平与其质量摩尔浓度成正比，并且通过冰点降低和蒸气压亏缺测量的值之间几乎没有不一致；（4）通过冰点降低测量的乙二醇水溶液和PEG水溶液的渗透压水平与通过蒸气压亏缺测量的值不同；（5）通过冰点降低测量的BSA水溶液的渗透压与通过蒸气压亏缺测量的值略有不同。
