A Bioinspired Threonine-based Antifreeze Protein Mimic with Potent Ice Recrystallization Inhibition Activity

Abstract

Ice growth mitigation is a pervasive challenge for multiple industries. In nature, ice-binding proteins (IBPs) demonstrate potent ice-growth prevention through ice recrystallization inhibition (IRI). However, IBPs are expensive, difficult to produce in large quantities, and exhibit minimal resilience to non-physiological environmental stressors, such as elevated pH. For these reasons, researchers have turned to polymeric bioinspired mimics. To-date, however, no mimic has rivaled the ability of native IBPs to display IRI activity at ultra-low nanomolar concentrations. In this work, we study the IRI activity of peptides and polypeptides inspired by common ice-binding residues of IBPs to inform the synthesis and characterization of a potent bioinspired polymer mimic. We show first that the threonine polypeptide (pThr) displays the best IRI activity in 2 phosphate-buffered saline (PBS). Second, we use pThr as a molecular model to synthesize and test a new bioinspired polymer mimic, poly(2-hydroxypropyl methacrylamide) (pHPMA). We show that pHPMA exhibits potent IRI activity in neutral PBS at nanomolar concentrations. These results substantiate that pHPMA outperforms poly(vinyl alcohol) (PVA), the current top performing IBP mimic in the field, in terms of effectiveness at mitigating ice crystal growth at concentrations akin to native IBPs.