Department of Biological Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, India.
Chemistry. 2010 Apr 26;16(16):4911-22. doi: 10.1002/chem.200903205.
Hydrogels of amino acid based cationic surfactant having C(16) tails were used to immobilize heme proteins and enzyme. These hydrogel-entrapped proteins/enzyme showed remarkable activation when dispersed in organic solvent. The activation effect (ratio of the activity of the hydrogel-entrapped enzyme in organic solvent to the activity of the native enzyme in water) of cytochrome c increased up to 350-fold with varying protein and gelator concentration. Hydrogel-entrapped hemoglobin and horseradish peroxidase (HRP) also showed markedly improved activity in organic solvent. Alteration in the structure of the gelator and its supramolecular arrangement showed that the protein immobilized within amphiphilic networks with larger interstitial space exhibited higher activation. This striking activation of hydrogel-entrapped proteins stems from the following effects: 1) the hydrophilic domain of the amphiphilic networks facilitates accessibility of the enzyme to the water-soluble substrate. 2) the surfactant, as an integral part of the amphiphilic network, assists in the formation of a distinct interface through which reactants and products are easily transferred between hydrophilic and hydrophobic domains. 3) Surfactant gelators help in the dispersion and stabilization of gel matrix into small particles in organic solvent, which enhances the overall surface area and results in improved mass transfer. The activation was dramatically improved up to 675-fold in the presence of nongelating anionic surfactants that helped in disintegration of the gel into further smaller-sized particles. Interestingly, hydrogel-immobilized HRP exhibited about 2000-fold higher activity in comparison to the activity of the suspended enzyme in toluene. Structural changes of the entrapped enzyme and the morphology of the matrix were investigated to understand the mechanism of this activation.
氨基酸基阳离子表面活性剂的水凝胶被用于固定血红素蛋白和酶。这些水凝胶包埋的蛋白质/酶在有机溶剂中分散时表现出显著的激活作用。细胞色素 c 的激活效果（有机溶剂中水凝胶包埋酶的活性与水相中原酶的活性之比）随蛋白质和凝胶剂浓度的变化而增加了 350 倍。水凝胶包埋的血红蛋白和辣根过氧化物酶（HRP）在有机溶剂中也表现出明显提高的活性。凝胶剂结构及其超分子排列的改变表明，固定在具有较大间隙的两亲网络中的蛋白质表现出更高的活性。水凝胶包埋蛋白质的这种显著激活源于以下几个效应：1）两亲网络的亲水域促进了酶对水溶性底物的可及性。2）表面活性剂作为两亲网络的组成部分，通过形成一个独特的界面，有助于反应物和产物在亲水区和疏水区之间的容易传递。3）表面活性剂凝胶剂有助于凝胶基质在有机溶剂中分散和稳定为小颗粒，从而提高了整体表面积，并促进了传质。在非凝胶阴离子表面活性剂的存在下，激活作用显著提高了 675 倍，这有助于将凝胶分解成更小的颗粒。有趣的是，与悬浮在甲苯中的酶的活性相比，水凝胶固定化的 HRP 表现出约 2000 倍的更高活性。研究了包埋酶的结构变化和基质的形态，以了解这种激活的机制。
