Certain species native to colder environments (plants, fish, and insects) have adapted to their climate by producing antifreeze(glycol)proteins (AF(G)P) exhibiting either ice recrystallization inhibition (IRI), thermal hysteresis activity (THA), or both. Although several synthetic approaches for the exploitation of these proteins have been investigated, challenges remain in the synthetic design of biomimicsand in the unraveling of the relationships between mechanism and structure. With the goal of designing synthetic coatings that exhibit anti-icing behavior, we have approached a systematic series of target (macro)molecules carefully placing structure so as to elucidate the key mechanisms to ice interaction. Regarding analytical aspects, we will first describe our efforts to quantitatively optimize the analysis of both THA and IRI by differential scanning calorimetry (DSC), as well as to emphasize the importance of using molar as opposed to mass concentrations. With those methods, we will then contrast the performance of the AFP present in the desert beetle Anatolica polita (ApAFP752) in the solution state versus the same conjugated to synthetic polymer constructs suited to coating formation. Behavior as individual biomacromolecules in solution does not necessarily translate to solid-state performance. Next, we will contrast the same, but for what we believe to be key polypeptide sequences. And finally, drawing comparison between the distance between hydrogen bonding sites in threonine, a beta-sheet array of which is thought to be key to the ice interaction in ApAFP752, we also describe our bottom-up synthetic approach to position small organic molecules with similar dimensions and known anti-freeze properties (such as ethylene glycol, EG) pendent to a host polyol-based polymer chain. Here, where AFP behavior is noncolligative, the polymeric solid-state form of pendent-EG is thought to result in an effectively high concentration and thus freezing point depression. Here again, we explore the role of the pendent unit’s conformational freedom along with consideration of the distance between its hydrogen bond capable functional groups. In addition to IRI and THA by DSC, XRD ice crystal structure and microscopy assays are also used to characterize the ice IRI behavior. This study aims to pave the path for rational design of synthetic IRI polymers, useful for applications such as anti-icing coatings through to cryo-preservation methods for organ transport.

Polymer bioconjugates and polyol based polymers for ice recrystallization inhibition and thermal hysteresis activity in anti-icing coatings

2019 Fall National Meeting

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