Temperature dependence of the conformational properties of sodium-type gellan gum in aqueous solutions
Temperature dependence of the conformational properties of sodium-type gellan gum in aqueous solutions
复制标题
DOI：
10.1007/3-540-48349-7_2
复制
发表时间：
1999-01-01
期刊：
影响因子：
--
通讯作者：
Ogawa, E
中科院分区：
文献类型：
--
作者：
Ogawa, E
通过粘度测定法和渗透压测定法研究了水溶液中钠型结冷胶构象特性的温度依赖性。渗透压测量是在 28、40 和 45 °C 两种氯化钠浓度（cs= 25 和 50 mM）的水溶液中进行的。在 5 至 50 °C 的温度范围内，在三种氯化钠浓度（cs= 0.0、12.5 和 25 mM）和四种蔗糖浓度（csu= 0.0、0.05、0.5 和 1.0 M）的水溶液中进行粘度测量。在不同cs的氯化钠水溶液中在40和45℃下获得的Mn值几乎一致，并且平均值(5.7×104)略小于28℃下获得的Mn值(13.6×104)的一半，这表明在28℃下发生两个分子的缔合且仅发生部分缔合体聚集。降低温度时，氯化钠溶液的粘度值ηsp/c在较高温度区域仅略微增加，但在临界温度以下急剧增加，该临界温度随着cs的增加而增加，并且在这些临界温度以下几度时，ηsp/c值逐渐增加。相比之下，对于水溶液，ηsp/c值在较高温度区域仅略有增加，但在临界温度以下急剧增加。蔗糖溶液的ηsp/c的温度依赖性与水溶液的相似，但蔗糖溶液的临界温度随着csu的增加而增加。这些结果可以解释为，在降低温度时，钠型结冷胶分子的卷曲到双螺旋构象转变和螺旋的部分聚集发生在临界温度以下，并且通过增加氯化钠或蔗糖浓度来促进。
The temperature dependence of the conformational properties of sodium-type gellan gum in aqueous solutions was studied by viscometry and osmometry. The osmometry measurements were made at 28, 40, and 45 °C in aqueous solutions at two sodium chloride concentrations (cs= 25 and 50 mM). Viscosity measurements were carried out over the temperature range from 5 to 50 °C in aqueous solutions at three sodium chloride concentrations (cs= 0.0, 12.5, and 25 mM) and four sucrose concentrations (csu= 0.0, 0.05, 0.5, and 1.0 M). TheMnvalues obtained at 40 and 45 °C in aqueous sodium chloride solutions with differentcswere almost coincident and the average value (5.7 × 104) was slightly less than half of theMnvalue (13.6 × 104) obtained at 28 °C, suggesting that association of two molecules and only a partial aggregation of associates take place at 28 °C. On lowering the temperature, the viscosity number,ηsp/c, of the sodium chloride solutions increased only slightly over the higher temperature regions but increased drastically below a critical temperature which increased with increasingcsand several degrees below these critical temperatures theηsp/cvalues increased gradually. For aqueous solutions, in contrast, theηsp/cvalues showed only a slight increase over higher temperature regions but a steep increase below the critical temperatures. The temperature dependence ofηsp/cfor the sucrose solutions was similar to that of the aqueous solutions, but the critical temperatures in sucrose solutions increased with increasingcsu. These results could be interpreted as showing that, on lowering the temperature, the coil-to-double helix conformational transition of sodium-type gellan molecules and partial aggregation of helices occur below the critical temperatures, and are promoted by increasing the sodium chloride or sucrose concentrations.