Polymers are often conjugated to proteins to improve stability; however, the impact of polymer chain length and functional groups on protein structure and function is not well understood. Here we use RAFT polymerization to grow polymers of different lengths and functionality from a short acrylamide oligomer with a RAFT end group conjugated to lysozyme. We show by X-ray crystallography that enzyme structure is minimally impacted by modification with the RAFT end group. Significant activity toward the negatively charged Micrococcus lysodeicticus cell wall was maintained when lysozyme was modified with cationic polymers. Thermal and chemical stability of the conjugates was characterized using differential scanning fluorimetry and tryptophan fluorescence. All conjugates had a lower melting temperature; however, conjugates containing ionic or substrate mimicking polymers were more resistant to denaturation by guanidine hydrochloride. Our results demonstrate that tailoring polymer functionality can improve conjugate activity and minimize enzymatic inactivation by denaturants.
聚合物常与蛋白质共轭以提高其稳定性;然而,聚合物链长和官能团对蛋白质结构和功能的影响尚未完全明了。本研究利用可逆加成断裂链转移(RAFT)聚合技术,从共轭于溶菌酶的带有RAFT端基的短
丙烯酰胺寡聚体出发,合成了不同长度和官能化的聚合物。通过X射线晶体学分析表明,RAFT端基修饰对酶结构的影响微乎其微。溶菌酶经阳离子聚合物修饰后,对带负电的藤黄微球菌细胞壁仍保持显著活性。采用差示扫描荧光法和色
氨酸荧光对共轭物的耐热性和
化学稳定性进行了表征。所有共轭物的熔解温度均较低;然而,含有离子或模拟底物聚合物的共轭体对
盐酸胍引起的变性具有更强的抵抗力。研究结果表明,通过调整聚合物官能团可以提高共轭物活性并减少酶因变性剂引起的失活。