Wan Abdul Khodir Wan Khairunnisa, Hakim Azizul, Kobayashi Motoyoshi
Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba 305-8572, Ibaraki, Japan.
Department of Soil Science, University of Chittagong, Chittagong 4331, Bangladesh.
Polymers (Basel). 2020 Aug 7;12(8):1770. doi: 10.3390/polym12081770.
Aggregation and aggregates properties of natural organic and nanosized macromolecules such as humic substances and proteins are crucial to explore so-called colloid-mediated transport and the fate of substances in soil and water environments. Therefore, the aggregation and dispersion, charging, and floc strength of lysozyme (LSZ)-leonardite humic acid (LHA) flocs were experimentally investigated. The experiments were performed in different salt concentrations and LSZ to LHA mass ratios as a function of pH. We obtained the stronger flocs at pH 4.4, where the isoelectric point (IEP) of the complex with the mass ratio 2.5 was confirmed. Thus, the aggregation of LSZ-LHA flocs is mainly caused by charge neutralization. We obtained the floc strength of 4.7 nN around IEP at low salt concentration of 3 mM, which was stronger than 2.8 nN in high salt concentration of 50 mM. The effect of salt concentration can be rationalized by charge-patch attraction at low salt concentration. With increasing mass ratio, the IEP shifted to higher pH. This is due to the increase in positive charge from LSZ in the mixture. The effect of the LSZ to LHA mass ratio on the maximum strength was weak in the range studied.
天然有机和纳米级大分子（如腐殖质和蛋白质）的聚集及聚集体性质对于探索所谓的胶体介导传输以及物质在土壤和水环境中的归宿至关重要。因此，对溶菌酶（LSZ）- 风化煤腐殖酸（LHA）絮体的聚集与分散、带电情况及絮体强度进行了实验研究。实验在不同盐浓度和LSZ与LHA质量比条件下进行，作为pH的函数。在pH 4.4时我们得到了更强的絮体，在此处证实了质量比为2.5的复合物的等电点（IEP）。因此，LSZ-LHA絮体的聚集主要由电荷中和引起。在3 mM的低盐浓度下，我们在IEP附近获得了4.7 nN的絮体强度，这比50 mM的高盐浓度下的2.8 nN更强。低盐浓度下的电荷补丁吸引力可以合理解释盐浓度的影响。随着质量比增加，IEP向更高pH移动。这是由于混合物中LSZ的正电荷增加。在所研究的范围内，LSZ与LHA质量比对最大强度的影响较弱。
