Bovine carbonic anhydrase (BCA) can be caused to aggregate and precipitate upon heating. In this paper, using a hydrophobic fluorescent reporter dye (ANS) which is commonly used to assay the presence of hydrophobic surfaces in proteins, we show that ANS can function like a small molecule chaperone. ANS can bind to both partially-unfolded, or partially-folded, BCA being subjected to thermal unfolding or refolding, and prevent the protein’s aggregation through the steric blocking of hydrophobic aggregation-prone surfaces. Using ANS, we were able to completely unfold BCA without any attendant aggregation and also refold it back to active state.

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