Aiba S
Biomimetic Chemistry Division, Industrial Products Research Institute, Ibaraki, Japan.
Int J Biol Macromol. 1989 Aug;11(4):249-52. doi: 10.1016/0141-8130(89)90077-9.
The stability of the solutions of partially N-acetylated chitosans was studied by two methods: (1) 1% solutions of the chitosan derivatives in 0.1 M aqueous acetic acid were added dropwise to buffer solutions with pH from 8.6 to 12 and to a 0.1 M NaOH solution; (2) to each 0.5% solution of the derivatives in 0.1 M acetic acid was added the desired amount of a 1 M NaOH solution. The stability data obtained were summarized with respect to the degree of N-acetylation. It was found that the solutions of the derivatives with more than 50% acetyl content were stable even in alkaline conditions and the gelation and precipitation of the solutions did not occur. The reactivity of the derivatives with the degree of N-acetylation of more than 50% was studied using methyl 4-azidobenzoimidate (MABI) and ethylene glycol diglycidyl ether in homogeneous states. It was found that MABI reacted with amino groups of the chitosans only at neutral pH and glycidyl groups reacted at neutral and alkaline pH. It seems that these unique properties of chitosans with a degree of N-acetylation of more than 50% will enable us to prepare new chitosan derivatives.
采用两种方法研究了部分N - 乙酰化壳聚糖溶液的稳定性：（1）将壳聚糖衍生物在0.1 M乙酸水溶液中的1%溶液逐滴加入到pH值为8.6至12的缓冲溶液和0.1 M氢氧化钠溶液中；（2）向0.1 M乙酸中各0.5%的衍生物溶液中加入所需量的1 M氢氧化钠溶液。所得稳定性数据根据N - 乙酰化程度进行了总结。结果发现，乙酰含量超过50%的衍生物溶液即使在碱性条件下也很稳定，溶液不会发生凝胶化和沉淀。使用4 - 叠氮基苯甲酸甲酯（MABI）和乙二醇二缩水甘油醚在均相状态下研究了N - 乙酰化程度超过50%的衍生物的反应活性。结果发现，MABI仅在中性pH下与壳聚糖的氨基反应，而缩水甘油基在中性和碱性pH下反应。看来，N - 乙酰化程度超过50%的壳聚糖的这些独特性质将使我们能够制备新的壳聚糖衍生物。
