Carbodiimide‐Fueled Assembly of π‐Conjugated Peptides Regulated byElectrostatic Interactions

Abstract

What prompted you to investigate this topic?Conjugated polymers and oligomers with unique optoelectronic properties are commonly processed using organic solvents, which can limit their utility for biological applications. As a result, side chain engineering with water-soluble biomolecules has been employed as an approach in the past years to achieve stimuli-triggered formation of functional assemblies of πconjugated systems under aqueous environments. However, several strategies to trigger H-bonding-mediated assembly of biomolecules in water often involve environmental changes that are far from physiological conditions, such as extreme changes in pH and ionic strength. Moreover, these biomolecular H-bonding interactions have been traditionally driven by external stimuli that most often reflect binary "on-off" states, despite peptides and proteins dynamically assembling and reassembling in response to chemical fuels under native biological environments. With these considerations in mind, we sought to recapitulate the natural fuel-driven processes for biomolecules in a synthetic material system designed for a targeted function. Specifically, we studied a carbodiimide-fueled pathway for instructing the monomers of semiconducting πconjugated peptides to assemble under aqueous conditions without relying on extreme changes in pH or ionic strength. This supramolecular system was also used as a model to demonstrate that we can use the peptide sequence to encode how the assembly-disassembly process can be tuned in water. What is the most significant result of this study?This study demonstrates the first example of a carbodiimidefueled assembly of peptidic monomers bearing a semiconducting unit. Importantly, our results show the molecular design-dependent conditions by which assembly and disassembly processes start to occur. We also show that the morphologies that can be accessed through this fuel-driven approach are distinct from the structures afforded by pH-driven assemblies.

Selective Induction of Molecular Assembly to Tissue‐Level Anisotropy on Peptide‐Based Optoelectronic Cardiac Biointerfaces

“…Structural models were built using 20 molecules of DDD-4T or DGRDDD-4T with twisted stacked structures and further optimized based on reported structural models (Figure 2c,d; and Figure S7, Supporting Information). [49,[52][53][54] The optimized structures clearly show the chiral nature of the stacking in DDD-4T and DGRDDD-4T, agreeing well with the CD results. Benefiting from the designed molecular structures, the central 𝜋-𝜋 stacking of quaterthiophenes is projected to enable photocurrent generation and support electron/exciton transport.…”

“…[46,47] These two quaterthiophene-functionalized peptides were synthesized according to the reported procedures using on-resin coupling (Figures S1,S2,S3,S4, see more details in the Supporting Information). [48,49] The central conjugated unit, 4T, and peptide termini together are capable of not only assembling into 1D nanostructures through 𝜋-interactions and hydrogen bonds, but also of facilitating electronic and ionic charge transport. [49,50] On the other hand, a widely used conjugated polymer, poly(3-hexylthiophene) (P3HT), was adopted as the substrate template material due to the similar conjugated backbone with the quaterthiophene core of the peptide units.…”

“…[48,49] The central conjugated unit, 4T, and peptide termini together are capable of not only assembling into 1D nanostructures through 𝜋-interactions and hydrogen bonds, but also of facilitating electronic and ionic charge transport. [49,50] On the other hand, a widely used conjugated polymer, poly(3-hexylthiophene) (P3HT), was adopted as the substrate template material due to the similar conjugated backbone with the quaterthiophene core of the peptide units. The 𝜋-interactions between quaterthiophene and polythiophene are leveraged here to facilitate peptide-surface interactions, guiding the self-assembly process on the polymeric substrate (Figure 1).…”

Selective induction of molecular- to tissue-level anisotropy on peptide-based optoelectronic cardiac biointerfaces

“…[43,44] These two quaterthiophene-functionalized peptides were synthesized according to the reported procedures using on-resin coupling (Figure S1, S2, and S3, see more details in the Supporting Information). [45,46] The central conjugated unit, 4T, and peptide termini together are capable of assembling into 1D nanostructures through π-interactions and hydrogen bonds. [46,47] On the other hand, a widely used conjugated polymer, poly(3-hexylthiophene) (P3HT), was adopted as the substrate template material due to the similar conjugated backbone with the quaterthiophene core of the peptide units.…”

“…[45,46] The central conjugated unit, 4T, and peptide termini together are capable of assembling into 1D nanostructures through π-interactions and hydrogen bonds. [46,47] On the other hand, a widely used conjugated polymer, poly(3-hexylthiophene) (P3HT), was adopted as the substrate template material due to the similar conjugated backbone with the quaterthiophene core of the peptide units. The π-interactions between quaterthiophene and polythiophene could therefore facilitate peptide-surface interactions, guiding the self-assembly process on the polymeric substrate (Figure 1).…”