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首页> 外文期刊>RSC Advances >Thermo-reversibility, ergodicity and surface charge–temperature dependent phase diagram of anionic, cationic and neutral co-gels of gelatin–BSA complexes
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Thermo-reversibility, ergodicity and surface charge–temperature dependent phase diagram of anionic, cationic and neutral co-gels of gelatin–BSA complexes

机译：明胶 - BSA复合物的阴离子，阳离子和中性共凝胶的热反转性，ergodicity和表面电荷 - 温度依赖性相图

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We have investigated the gelation behavior of polyampholyte gelatin B (GB) in the presence of colloidal plasma protein bovine serum albumin (BSA) as a function of mixing ratio ( r = GB?:?BSA = 1.5, 2, 3, 4), pH (acidic, basic and neutral), and temperature (20–45 °C). Both the bio-molecules have identical isoelectric pH, and similar zeta potential profiles. Formation of a BSA–GB intermolecular complex arising from hydrogen bonding, and surface selective patch binding between the flexible gelatin chain and colloidal protein BSA, with BSA acting as junction zones was probed. We observed the cationic, neutral and anionic gelation occurring at pHs (3, 5 and 7) corresponding to surface charge of the intermolecular complexes (seen through their zeta potential, ζ ). The kinetics and dynamics of gelation were observed from the intensity of scattered light, and time-correlation function which evolved with waiting time ( t _(w) ≥ t _(gel) ), and indicated rapid gelation for pH 5 (neutral gels) compared to other sols at pH 7 (anionic gel) while at pH 3 (cationic gel) very slow gelation was evident. For all gels with a waiting time of t _(w) → ∞ the gels moved from an ergodic to non-ergodic state. At t _(w) = 0 (nascent gel), the correlation function exhibited a single relaxation mode due to the system residing deeply inside the ergodic phase, and mirroring purely Brownian dynamics. After a characteristic waiting time (ergodicity breaking time, τ _(EB) ), an additional relaxation (slow mode) appeared which was attributed to inter-chain interactions induced by reorganization of entanglements. The rigidity (low frequency storage modulus, G _(0) ), and melting temperature T _(m) of neutral gels was higher than anionic, but was least for cationic gels. Finally, we capture a unique surface charge versus temperature ( ζ vs. T ) phase diagram at different pHs, and noticed thermally activated phase transitions which indicated multiple self-assembled states of this pair of bio-molecules leading to evolution of several new soft matter phases, all of which were not thermo-reversible.
机译：我们在胶体血浆蛋白牛血清白蛋白（BSA）存在下作为混合比的函数（R = GB？：β= 1.5,2,3,4），研究了多聚胺蛋白牛蛋白牛血清白蛋白（BSA）的凝胶化行为（BSA）。 pH（酸性，碱性和中性）和温度（20-45°C）。生物分子都具有相同的等电pH和类似的Zeta电位谱。探测了氢粘合剂产生的BSA-GB分子分子复合物，以及柔性明胶链和胶体蛋白BSA之间的表面选择性贴剂，用BSA作用作为结区。我们观察到对应于分子间复合物的表面电荷的pH（3,5和7）处发生的阳离子，中性和阴离子凝胶化（通过它们通过它们的Zeta电位观察）。从散射光的强度观察到凝胶化的动力学和动力学，以及随着等待时间演变的时间相关函数（T _（w）≥T_（凝胶）），并表明pH 5的快速凝胶化（中性凝胶）与pH7（阴离子凝胶）的其他溶胶相比，而在pH 3（阳离子凝胶）中非常慢凝胶化是显而易见的。对于具有T _（w）的等待时间的所有凝胶→∞∞凝胶从ergodic移动到非遍历状态。在T _（w）= 0（新凝胶）中，相关函数由于围住遍历相位内的系统，并且镜像纯粹的布朗动力学，因此表现出单个弛豫模式。在特征等待时间（ergodicity断裂时间，τ_（eb））之后，出现了额外的松弛（慢速模式），其归因于通过重组纠缠引起的链间相互作用。中性凝胶的刚性（低频储存模量，G _（0））和熔融温度T _（m）高于阴离子，但是阳离子凝胶的凝胶。最后，我们捕获不同pHs的独特表面电荷与温度（ζ与ζT）相图，并注意到热敏的相变，这表明这对生物分子的多个自组装状态，导致几种新柔软物质的演变阶段，所有这些都不是热可逆的。

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