Abstract
Antifreeze (glyco) proteins are produced by many cold-acclimatized species to enable them to survive subzero temperatures. These proteins have multiple macroscopic effects on ice crystal growth which makes them appealing for low-temperature applications—from cellular cryopreservation to food storage. Poly(vinyl alcohol) has remarkable ice recrystallization inhibition activity, but its mode of action is uncertain as is the extent at which it can be incorporated into other high-order structures. Here the synthesis and characterization of well-defined block copolymers containing poly(vinyl alcohol) and poly(vinylpyrrolidone) by RAFT/MADIX polymerization is reported, as new antifreeze protein mimetics. The effect of adding a large second hydrophilic block is studied across a range of compositions, and it is found to be a passive component in ice recrystallization inhibition assays, enabling retention of all activity. In the extreme case, a block copolymer with only 10% poly(vinyl alcohol) was found to retain all activity, where statistical copolymers of PVA lose all activity with very minor changes to composition. These findings present a new method to increase the complexity of antifreeze protein mimetic materials, while retaining activity, and also to help understand the underlying mechanisms of action.
Highlights
Antifreeze proteins (AF(G)Ps) are produced by species which live in extreme cold environments as an evolutionary adaptation to control the formation and growth of ice crystals, which would otherwise lead to death.[1]
Antifreeze proteins and glycoproteins are complex macromolecules which enable life to survive at extreme low temperatures, but their mechanism of action, and the mechanism of action of their synthetic mimics, is not understood
Quantitative ice recrystallization inhibition analysis on this library revealed that addition of the PVP block was essentially passive; it did not increase or decrease activity
Summary
Antifreeze (glyco) proteins (AF(G)Ps) are produced by species which live in extreme cold environments (i.e., the Earth’s poles or at high altitude) as an evolutionary adaptation to control the formation and growth of ice crystals, which would otherwise lead to death.[1]. The SEC Mn values obtained for PVP are underestimated, as DMF (or other standard SEC solvents) is not an ideal solvent for it, but dispersity values around 1.4 were observed, as would be expected for this monomer by RAFT/MADIX.37,38 1H NMR end-group analysis enabled estimation of the molecular weight by comparing the aromatic end-groups to the main chain, which were in agreement with that predicted from the conversion From this point on, the NMR degree of polymerization will be the stated value. Ben et al have studied several small molecule IRI active compounds and found IRI without any TH or DIS and using solid state NMR have found evidence that disruption of the quasi liquid layer interface may be the crucial mechanism of action to obtain IRI without ice binding.[39] There is speculation that PVA’s activity is due to its specific hydroxyl group spacing interfacing with the ice crystals, and disruption of the PVA primary sequence (as a copolymer, for example) reduces activity. The data presented here on relatively short PVAs may not scale with high molecular weight PVAs (which are extremely challenging to access using controlled radical polymerization), where ice shaping and thermal hysteresis is reported[22] and the key dependence on unbroken hydroxyl units suggests some specific interactions, which will form the basis of future studies
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
