On the self-​assembly of a tryptophan labeled deoxycholic acid

Self-​assembly of peptides and bile acids has been widely investigated because of their biol. role and their potential as a tool for the prepn. of nanostructured biomaterials. We herein report both the synthesis and the self-​assocn. behavior of a compd. that combines the aggregation properties of bile acid- and amino acid-​based mols. The deriv. has been prepd. by introducing a L-​tryptophan residue into the C-​3 position of the deoxycholic acid skeleton and resulted in an amphoteric fluorescent labeled bile acid that shows a pH-​dependent self-​assembly. Under alk. conditions it assembles into 28 nm diam. tubules, thus showing a completely different behavior compared to the precursor bile acid, which forms micelles under similar conditions. Upon heating the tubules break and turn into micelles, leading to an increase in the exposure to water of the tryptophan residue. On the other hand, in acidic solns. it aggregates into elongated micelles that further self-​assemble forming a gel network, when an electrolyte is added.