Polycarboxylates enhance beetle antifreeze protein activity

Area of Science:

• Biochemistry
• Protein Science
• Materials Science

Background:

• Antifreeze proteins (AFPs) reduce the freezing point of water, creating thermal hysteresis (TH).
• TH magnitude depends on AFP concentration, activity, and solution enhancers.
• Enhancers are typically low molecular mass molecules or proteins.

Purpose of the Study:

• To investigate polycarboxylates as enhancers for the thermal hysteresis activity of Dendroides canadensis antifreeze protein (DAFP).
• To identify structural features of polycarboxylates that influence their enhancer efficiency.

Main Methods:

• Differential scanning calorimetry (DSC) was used to measure the thermal hysteresis (TH) activity of DAFP.
• A series of polycarboxylates were tested as potential enhancers for DAFP.
• The effect of Zn(2+) coordination on enhancer activity was investigated.

Main Results:

• Triethylenetetramine-N,N,N',N'',N''',N'''-hexaacetate was identified as the most potent enhancer, increasing DAFP TH by 1.5-fold compared to citrate.
• Zn(2+) coordination abolished the enhancement ability of carboxylates.
• Enhancer efficiency correlated with the number of carboxylate groups and molecular flexibility; hydroxyl groups also contributed positively.

Conclusions:

• Polycarboxylates are effective enhancers of AFP thermal hysteresis activity.
• Molecular structure, specifically the number of carboxylate groups and freedom of motion, dictates enhancer efficiency.
• Metal coordination can inhibit the antifreeze-enhancing properties of polycarboxylates.