低浓度鼠李糖脂单糖脂在近中性溶液中的聚集行为

摘要

Size distribution of monorhamnolipid aggregates in neutral pH solutions with rhamnolipid concentration near critical micelle concentration (CMC) was studied. Aggregates were formed when rhamnolipid concentration was either below or above CMC. Three types of aggregates which were large (d=5000nm), medium (d=200~500nm) and small (d=40nm) in size were found. When pH was below 7.0 and the rhamnolipid concentration was below CMC, size of the medium-size aggregates decreased with increasing rhamnolipid concentration, and large-size and medium-size aggregates transformed into small-size aggregates. With the increase of solution pH, size of the medium-size aggregate also decreased, and large-size and medium-size aggregates transformed into small-size aggreqates. These observations were assumed to result from change of density and dissociation degree of monorhamnolipid molecule in the aggregates with rhamnolipid concentration and solution pH.%研究了临界胶束浓度(CMC)附近鼠李糖脂单糖脂在近中性溶液中的聚集体粒径分布。结果发现，单鼠李糖脂在低于CMC和高于CMC时均能形成聚集体，根据粒径大小分为粒径在5000nm左右的大粒子、200~500nm的中等粒子和40nm左右的小粒子。当pH≤7且浓度低于CMC时，中等粒子的粒径随单鼠李糖脂浓度增大而减小，且聚集体在分布上由大粒子向小粒子转变。随着 pH 值升高，中等粒子的粒径也同样由大变小，且分布上大粒子和中等粒子均向小粒子转变。该结果被认为是聚集体中的单鼠李糖脂分子密度和分子的离解性质随浓度或pH变化所致。