DYNAMICS OF PROBE COMPLEXATION TO BILE-SALT AGGREGATES

Excited triplet naphthalene and xanthone were employed as probe molecu les to study the dynamics of incorporation into sodium cholate, tauroc holate, and deoxycholate aggregates. The association and dissociation rate constants and the quenching rate constants for the incorporated p robes were recovered from the dependence of the observed triplet decay rate constants on quencher concentrations (nitrite and cupric ions). Triplet naphthalene was incorporated into a site offering a high degre e of protection from quenchers and from which dissociation was relativ ely slow. Triplet xanthone was incorporated into a less protected site from which dissociation was an order of magnitude faster than from th e naphthalene site. We propose that naphthalene was incorporated into the hydrophobic site of primary aggregates, and xanthone was located i n the region containing the hydroxyl groups in the secondary aggregate s.