Department of Chemistry, University of Warwick, Gibbet Hill Road, Coventry, United Kingdom, CV4 7AL.
Biomacromolecules. 2013 May 13;14(5):1578-86. doi: 10.1021/bm400217j. Epub 2013 Apr 10.
This manuscript reports a detailed study on the ability of poly(vinyl alcohol) to act as a biomimetic surrogate for antifreeze(glyco)proteins, with a focus on the specific property of ice-recrystallization inhibition (IRI). Despite over 40 years of study, the underlying mechanisms that govern the action of biological antifreezes are still poorly understood, which is in part due to their limited availability and challenging synthesis. Poly(vinyl alcohol) (PVA) has been shown to display remarkable ice recrystallization inhibition activity despite its major structural differences to native antifreeze proteins. Here, controlled radical polymerization is used to synthesize well-defined PVA, which has enabled us to obtain the first quantitative structure-activity relationships, to probe the role of molecular weight and comonomers on IRI activity. Crucially, it was found that IRI activity is "switched on" when the polymer chain length increases from 10 and 20 repeat units. Substitution of the polymer side chains with hydrophilic or hydrophobic units was found to diminish activity. Hydrophobic modifications to the backbone were slightly more tolerated than side chain modifications, which implies an unbroken sequence of hydroxyl units is necessary for activity. These results highlight that, although hydrophobic domains are key components of IRI activity, the random inclusion of addition hydrophobic units does not guarantee an increase in activity and that the actual polymer conformation is important.
本文详细研究了聚乙烯醇作为抗冻（糖）蛋白仿生替代物的能力，重点研究了其抑制冰晶重结晶（IRI）的特性。尽管已经进行了超过 40 年的研究，但生物抗冻剂作用的潜在机制仍未被很好地理解，部分原因是其有限的可用性和挑战性的合成。尽管聚乙烯醇（PVA）与天然抗冻蛋白在主要结构上存在显著差异，但它却显示出了显著的抑制冰晶重结晶的活性。在这里，我们使用可控自由基聚合来合成具有明确结构的 PVA，这使我们能够获得第一个定量的结构-活性关系，从而探究分子量和共聚单体对 IRI 活性的作用。至关重要的是，我们发现当聚合物链长从 10 个重复单元增加到 20 个重复单元时，IRI 活性“被开启”。聚合物侧链上亲水或疏水单元的取代会降低活性。与侧链修饰相比，对主链进行疏水修饰的容忍度稍高，这意味着活性需要连续的羟基单元。这些结果表明，尽管疏水结构域是 IRI 活性的关键组成部分，但随机引入额外的疏水单元并不能保证活性的提高，而且聚合物的实际构象很重要。
