Quantitative Efficacy Classification of Ice Recrystallization Inhibition Agents

Abstract

Experimental investigations of ice recrystallization inhibition (IRI) efficacy have been performed for a large number of different substances, including natural antifreeze proteins (AFP) and antifreeze glycoproteins (AFGP), several synthetic AFGP analogues, as well as synthetic polymers. Here we define IRI efficacy as that concentration at which the ice recrystallization rate is dominated by the IRI compound. The investigated 39 compounds show IRI efficacies from about 2 mmol L −1 for the least effective compound still showing activity to about 1 nmol L −1 , which corresponds to the highest efficacy found for natural AFGP samples. Hence, the assay employed allows for a quantitative comparison of IRI efficacy over a range of at least 6 orders of magnitude, thereby enabling studies of distinguishing effects induced by even subtle structural variations in AFGP analogues that were synthesized. Our results show that AFGP are by far the most effective IRI agents in our assay, and we surmise that this particular efficacy may be due to their disaccharide moieties. This supposition is supported by the fact that IRI efficacy is strongly reduced for monosaccharide AFGP analogues, as well as for AFGP analogues with acetyl-protected monosaccharide moieties.

Blocking rapid ice crystal growth through nonbasal plane adsorption of antifreeze proteins

“…The Clifton nanoliter cryoscopy (44), sonocrystallization (55), and IRI (21,22) experiments were performed as described elsewhere. All samples were measured in 20 mM Tris, pH 7.5 buffer, except MpAFP, which was measured in 20 mM Tris, 2 mM CaCl 2 , pH 7.5 buffer.…”

“…melting temperature of the sample (20)(21)(22). Recrystallization of ice involves ice grain boundary migration (20), in which large ice crystals increase in size and small crystals disappear (i.e., Ostwald ripening).…”

Influence of Polymer Chain Architecture of Poly(vinyl alcohol) on the Inhibition of Ice Recrystallization

“…The determined IRI effi cacy for the linear PVA ( C i = 46 μg mL −1 ) is in close agreement with reported literature values. [ 29 ] Surprisingly, the PVA bottlebrush has a similar IRI effi cacy as the linear PVA. Even though the polymer architecture is signifi cantly altered with the PVA side chains of the bottlebrush densely grafted, this does not seem to affect the IRI activity of the polymer.…”

Interaction of ice binding proteins with ice, water and ions

“…9 This inspired the design of biomimetic antifreezes for use in biomedical applications such as red blood cell preservation. 80,81 In an ice recrystallization inhibition (IRI) activity assay, a thin wafer of fine polycrystalline ice is annealed at a subzero temperature (typically À6 C) for several hours during which the time-evolution of the size of individual ice grains is analyzed by optical microscopy. The lowest IBP-concentration where ice recrystallization cannot be observed, the IRIendpoint, is often reported to describe the IRI activity of the IBP.…”

“…9,84 To quantitatively compare the IRI activity of ice-binding compounds, automated image analysis routines have been developed to monitor the time-evolution of the mean ice grain size, r, and mean largest grain size. 80,86,87 The Koop laboratory demonstrated that r 3 increases linearly with time in 45 wt. % sucrose solutions as predicted by Lifshitz-SlyosovWagner (LSW) theory [ Fig.…”