Ge Jun, Lu Diannan, Wang Jun, Yan Ming, Lu Yunfeng, Liu Zheng
Department of Chemical Engineering, Tsinghua University, Beijing 100084, China.
J Phys Chem B. 2008 Nov 13;112(45):14319-24. doi: 10.1021/jp8053923. Epub 2008 Oct 22.
The assembly of a monomer around an enzyme as the essential step in the fabrication of enzyme nanogel by in situ polymerization was illustrated by molecular dynamics simulation and evidenced by a fluorescence resonance energy transfer spectrum, using lipase/acrylamide as a model system. The subsequent polymerization generated a hydrophilic gel network which not only strengthened the protein structural integrity via multipoint linkage but also increased the number of intramolecular H-bonds of the encapsulated protein, as suggested by the blue shift of the fluorescence spectrum of the encapsulated lipase. This greatly enhanced the stability of lipase at high temperature, as experimentally demonstrated. The exclusion of polar solvent molecules from the encapsulated enzyme, in contrast to the enrichment of water molecules, due to the presence of a hydrophilic gel network was displayed. This established a hydrophilic microenvironment for the encapsulated protein and thus gave the encapsulated protein an enhanced tolerance to the organic solvent, as experimentally observed in the present study and reported elsewhere. These results have given a molecular insight into the enzyme nanogel as well as its high potential as a robust enzyme model for an expended application spectrum of enzymatic catalysis.
以脂肪酶/丙烯酰胺为模型体系，通过分子动力学模拟说明了单体围绕酶组装是原位聚合制备酶纳米凝胶的关键步骤，并通过荧光共振能量转移光谱得到了证实。随后的聚合反应生成了亲水性凝胶网络，该网络不仅通过多点连接增强了蛋白质的结构完整性，还增加了被包封蛋白质分子内氢键的数量，这从被包封脂肪酶荧光光谱的蓝移可以看出。如实验所示，这极大地提高了脂肪酶在高温下的稳定性。与水分子富集相反，由于亲水性凝胶网络的存在，极性溶剂分子被排除在被包封的酶之外。这为被包封的蛋白质建立了一个亲水性微环境，从而使被包封的蛋白质对有机溶剂具有更高的耐受性，正如本研究中实验观察到的以及其他地方所报道的那样。这些结果从分子层面深入了解了酶纳米凝胶，以及它作为一种强大的酶模型在扩展酶催化应用范围方面的巨大潜力。
