Reversible peptide particle formation using a mini amino acid sequence

Interest in nanostructures, artificial compartments and smart materials is steadily increasing as a result of beneficial applications in sensors, tissue engineering, nanoreactors and drug delivery systems. Block copolymers, peptide-based hybrid materials, expressed protein-like copolymers, and peptides that self-assemble in aq. soln. fulfill the demands of such applications while providing max. biocompatibility. Herein, the authors focus on the formation of self-assembled particles using an amphiphilic amino acid (AA) sequence derived by solid-phase peptide synthesis (SPPS) and describe its purifn. and characterization. The prepd. undecamer features a repetitive L-tryptophan and D-leucine [LW-DL] motif representing the hydrophobic block, and an N-terminally attached hydrophilic (lysine or acetylated lysine) section. For peptides contg. charged lysine, aggregation into micelles and a minor fraction of peptide particles was obsd. Charge shielding with anionic counter ions shifted the equil. towards the larger peptide aggregates, with their size depending on the counter ion's position in the Hofmeister series. Similarly, the corresponding uncharged (acetylated) peptide was also demonstrated to assemble into micelles and subsequently into peptide particles, termed peptide beads', which the authors hypothesise to be multicompartment micelles. The formation of the peptide beads was studied as a function of temp. and solvent compn. by ESR, dynamic and static light scattering, fluorometry and electron microscopy. The results suggest an equil. between single peptide mols., micelles, and peptide beads. Interestingly once formed the peptide beads show high mech. stability and preserve their shape and dimensions even after isolation from soln. [on SciFinder(R)]