Publications

Deboronation is observed during the reductive amination of formylphenylboronic acid (FPBA) to the amine termini and side chains of peptides. This deboronation is sensitive to the isomerism of the boronic acid (BA), with ortho-FPBA yielding complete deboronation in the preparation of an N-terminally-modified dipeptide. The observed behavior is also clearly mediated by the chemical identity of the amine substrate. These results reveal a previously undocumented subtlety of BA functionalization and highlight the importance of thorough spectroscopic characterization in the preparation of peptide and small molecule BAs.

Modification of the dipeptide of phenylalanine, FF, with a boronic acid (BA) functionality imparts unique aqueous self-assembly behavior that responds to multiple stimuli. Changes in pH and ionic strength are used to trigger hydrogelation via the formation of nanoribbon networks. Furthermore, we show for the first time that the binding of polyols to the BA functionality can modulate a peptide between its assembled and disassembled states.

Triblock amphiphilic molecules composed of three distinct segments provide a large parameter space to obtain self-assembled structures beyond what is achievable with conventional amphiphiles. To obtain a molecular understanding of the thermodynamics of self-assembly, we develop a coarse-grained triblock polymer model and apply self-consistent field theory to investigate the packing mechanism into layer structures. By tuning the structural and interaction asymmetry, we are able to obtain bilayers and monolayers, where the latter may additionally be mixed (symmetric) or segregated (asymmetric). Of particular interest for a variety of applications are the asymmetric monolayers, where segregation of end blocks to opposite surfaces is expected to have important implications for the development of functional nanotubes and vesicles with distinct surface chemistries.

The secondary structure of peptides in the presence of interacting additives is an important topic of study, having implications in the application of peptide science to a broad range of modern technologies. Surfactants constitute a class of biologically relevant compounds that are known to influence both peptide conformation and aggregation or assembly. We have characterized the secondary structure of a linear nonapeptide composed of a hydrophobic alanine/phenylalanine core flanked by hydrophilic acid/amine units. We show that the anionic surfactant sodium dodecyl sulfate (SDS) induces the formation of β-sheets and macroscopic gelation in this otherwise unstructured peptide. Through comparison to related additives, we propose that SDS-induced secondary structure formation is the result of amphiphilicity created by electrostatic binding of SDS to the peptide. In addition, we demonstrate a novel utility of surfactants in manipulating and stabilizing peptide nanostructures. SDS is used to simultaneously induce secondary structure in a peptide and to inhibit the activity of a model enzyme, resulting in a peptide hydrogel that is impervious to enzymatic degradation. These results complement our understanding of the behavior of peptides in the presence of interacting secondary molecules and provide new potential pathways for programmable organization of peptides by the addition of such components.

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