Effect of pH on the activity of ice-binding protein from Marinomonas primoryensis

The ability of an ice-binding protein (IBP) from Marinomonas primoryensis ( Mp IBP) to influence ice crystal growth and structure in nonphysiological pH environments was investigated in this work. The ability for Mp IBP to retain ice interactivity under stressed environmental conditions was determined via (1) a modified splat assay to determine ice recrystallization inhibition (IRI) of polycrystalline ice and (2) nanoliter osmometry to evaluate the ability of Mp IBP to dynamically shape the morphology of a single ice crystal. Circular dichroism (CD) was used to relate the IRI and DIS activity of Mp IBP to secondary structure. The results illustrate that Mp IBP secondary structure was stable between pH 6 and pH 10. It was found that Mp IBP did not interact with ice at pH ≤ 4 or pH ≥ 13. At 6 ≤ pH ≥ 12 Mp IBP exhibited a reduction in grain size of ice crystals as compared to control solutions and demonstrated dynamic ice shaping at 6 ≤ pH ≥ 10. The results substantiate that Mp IBP retains some secondary structure and function in non-neutral pH environments; thereby, enabling its potential utility in nonphysiological materials science and engineering applications.