bis-ANS is a high-affinity non-covalent extrinsic fluorescent dye used to analyze protein conformation.[1] Its predominant interaction with proteins is through its hydrophobic phenyl and naphthyl rings.[2] bis-ANS has an excitation maxima of 390 nm.[3] It has an emission maximum of 523 nm when free in solution but undergoes a blue shift with an increase in fluorescence intensity when bound to protein; for example, when bound to intestinal fatty acid binding protein (FAPB2) it has emission maxima of 484-496 nm. bis-ANS has been used to label mechanically damaged neurons in acute brain slices.4 It also potently inhibits microtubule assembly.[5],[6]

Reference:
[1]. Hawe, A., Sutter, M., and Jiskoot, W. Extrinsic fluorescent dyes as tools for protein characterization. Pharm. Res. 25(7), 1487-1499 (2008).
[2]. Bothra, A., Bhattacharyya, A., Mukhopadhyay, C., et al. A fluorescence spectroscopic and molecular dynamics study of bis-ANS/protein interaction. J. Biomol. Struct. Dyn. 15(5), 959-966 (1998).
[3]. Pastukhov, A.V., and Ropson, I.J. Fluorescent dyes as probes to study lipid-binding proteins. Proteins 53(3), 607-615 (2003).
[4]. Mozes, E., Hunya, A., Toth, A., et al. A novel application of the fluorescent dye bis-ANS for labeling neurons in acute brain slices. Brain Res. Bull. 86(3-4), 217-221 (2011).
[5]. Horowitz, P., Prasad, V., and Luduena, R.F. Bis(1,8-anilinonaphthalenesulfonate). A novel and potent inhibitor of microtubule assembly. J. Biol. Chem. 259(23), 14647-14650 (1984).
[6]. Mazumdar, M., Parrack, P.K., Mukhupadbhyay, K., et al. Bis-ANS as a specific inhibitor for microtubule-associated protein induced assembly of tubulin. Biochemistry 31(28), 6470-6474 (1992).