Tiwari Preeti, Bharti Indu, Bohidar Himadri B, Quadir Shabina, Joshi Mohan C, Arfin Najmul
Soft condense matter laboratory, Centre for Interdisciplinary Research In Basic Sciences, Jamia Millia Islamia, New Delhi 110025, India.
School of Physical Sciences, Jawaharlal Nehru University, New Delhi 110067, India.
ACS Omega. 2020 Dec 16;5(51):33064-33074. doi: 10.1021/acsomega.0c04647. eCollection 2020 Dec 29.
In this paper, for the first time, we have reported the formation of complex coacervate during interaction between hydrophobic protein, zein, and hydrophilic nanoclay, Laponite, in a 60% v/v ethanol solution at pH 4. Dynamic light scattering and viscosity measurements revealed the formation of zein-Laponite complexes during the interaction between zein at fixed concentration, = 1 mg/mL, and varying concentrations of Laponite, (7.8 × 10 - 0.25% w/v). Further investigation of the zein-Laponite complexes using turbidity and zeta potential data showed that these complexes could be demarcated in three different regions: Region I, below the charge neutralization region ( = 1 mg/mL, ≤ 0.00625% w/v) where soluble complexes was formed during interaction between oppositely charged zein and Laponite; Region II, the charge neutralization region ( = 1 mg/mL, 0.00625 < ≤ 0.05% w/v) where zein-Laponite complexes form neutral coacervates; and Region III, the interesting overcharged coacervates region ( = 1 mg/mL, > 0.05% w/v). Investigation of coacervates using a fluorescence imaging technique showed that the size of neutral coacervates in region II was large (mean size = 1223.7 nm) owing to aggregation as compared to the small size of coacervates (mean size = 464.7 nm) in region III owing to repulsion between overcharged coacervates. Differential scanning calorimeter, DSC, revealed the presence of an ample amount of bound water in region III. The presence of bound water was evident from the presence of an additional peak at 107 °C in region III apart from normal enthalpy of evaporation of water from coacervates.
在本文中，我们首次报道了在pH值为4的60% v/v乙醇溶液中，疏水性蛋白质玉米醇溶蛋白（zein）与亲水性纳米黏土锂皂石（Laponite）相互作用时形成了复合凝聚层。动态光散射和粘度测量结果表明，在固定浓度（= 1 mg/mL）的玉米醇溶蛋白与不同浓度（7.8×10 - 0.25% w/v）的锂皂石相互作用过程中，形成了玉米醇溶蛋白-锂皂石复合物。利用浊度和zeta电位数据对玉米醇溶蛋白-锂皂石复合物进行的进一步研究表明，这些复合物可分为三个不同区域：区域I，低于电荷中和区域（= 1 mg/mL，≤ 0.00625% w/v），在此区域，带相反电荷的玉米醇溶蛋白和锂皂石相互作用时形成可溶性复合物；区域II，电荷中和区域（= 1 mg/mL，0.00625 <≤ 0.05% w/v），在此区域，玉米醇溶蛋白-锂皂石复合物形成中性凝聚层；区域III，有趣的过电荷凝聚层区域（= 1 mg/mL，> 0.05% w/v）。使用荧光成像技术对凝聚层进行的研究表明，由于聚集作用，区域II中中性凝聚层的尺寸较大（平均尺寸 = 1223.7 nm），而区域III中凝聚层的尺寸较小（平均尺寸 = 464.7 nm），这是由于过电荷凝聚层之间的排斥作用。差示扫描量热仪（DSC）显示区域III中存在大量结合水。除了凝聚层中水蒸发的正常焓值外，区域III中在107 °C处出现的额外峰表明存在结合水。
