The hydrophobic probe 4,4'-bis(1-anilino-8-naphthalene sulfonic acid) is specifically photoincorporated into the N-terminal domain of alpha B-crystallin.

Photoincorporation of the fluorescent probe 4,4'-bis(1-anilino-8-naphthalene sulfonic acid) (bis-ANS) can be used to locate solvent-exposed hydrophobic regions in proteins. We show that bis-ANS is specifically incorporated into the putative N-terminal domain of alpha B-crystallin. This incorporation diminishes the chaperone-like activity of alpha B-crystallin, suggesting that hydrophobic surfaces in the N-terminal domain are involved in the binding of unfolding proteins.