Institute of Food Research, Norwich Research Park, Colney, Norwich, United Kingdom.
Biomacromolecules. 2011 Feb 14;12(2):359-69. doi: 10.1021/bm1011213. Epub 2010 Dec 20.
The effect of pH on the stability of layer-by-layer deposited polygalacturonic acid (PGalA)-based multilayer films prepared with the polycations poly-L-lysine, chitosan, and lysozyme is studied. The response was characterized using a quartz crystal microbalance, dual polarization interferometry, and Fourier transform infrared spectroscopy which probe multilayer thickness, density, polymer mass (composition and speciation), and hydration. All multilayers showed irreversible changes in response to pH change becoming thinner due to the partial disassembly. Preferential loss of the polycation (50-80% w/w) and relative small losses of PGaLA (10-35% w/w) occurred. The charge density on the polycation has a strong influence on the response to the acid cycle. Most of the disassembly takes place at the pH lower that pK(a) of PGaLA, indicating that this factor was crucial in determining the stability of the films. The pH challenge also revealed a polycation-dependent shift to acid pH in the PGaLA pK(a).
研究了 pH 值对聚半乳糖醛酸（PGalA）基层层沉积多聚阳离子（聚-L-赖氨酸、壳聚糖和溶菌酶）多层膜稳定性的影响。使用石英晶体微天平、双偏振干涉测量法和傅里叶变换红外光谱法对响应进行了表征，这些方法分别探测多层厚度、密度、聚合物质量（组成和形态）和水合作用。所有多层膜对 pH 值变化的响应均表现出不可逆的变化，由于部分解组装而变薄。聚阳离子（50-80%w/w）优先损失，而 PGalA 相对较小损失（10-35%w/w）。聚阳离子的电荷密度对酸循环的响应有很强的影响。大部分解组装发生在低于 PGalA pK(a)的 pH 值下，这表明该因素在确定膜的稳定性方面至关重要。pH 值挑战还揭示了聚阳离子依赖性的 PGalA pK(a)向酸性 pH 值的偏移。
