Ice Recrystallization Inhibition by Amino Acids: The Curious Case of Alpha- and Beta-Alanine

Extremophiles produce macromolecules which inhibit ice recrystallization, but there is increasing interest in discovering and developing small molecules that can modulate ice growth. Realizing their potential requires an understanding of how these molecules function at the atomistic level. Here, we report the discovery that the amino acid L-alpha-alanine demonstrates ice recrystallization inhibition (IRI) activity, functioning at 100 mM (similar to 10 mg/mL). We combined experimental assays with molecular simulations to investigate this IRI agent, drawing comparison to beta-alanine, an isomer of L-alpha-alanine which displays no IRI activity. We found that the difference in the IRI activity of these molecules does not originate from their ice binding affinity, but from their capacity to (not) become overgrown, dictated by the degree of structural (in)compatibility within the growing ice lattice. These findings shed new light on the microscopic mechanisms of small molecule cryoprotectants, particularly in terms of their molecular structure and overgrowth by ice.

Automated summary

In this study, the researchers discovered that the amino acid L-alpha-alanine exhibits ice recrystallization inhibition activity. Through experimental assays and molecular simulations, they found that the difference in the inhibition activity between L-alpha-alanine and beta-alanine is not due to their ice binding affinity, but rather their capacity to become overgrown by ice. These findings shed new light on the microscopic mechanisms of small molecule cryoprotectants.