108475-17-8Relevant academic research and scientific papers
Variation of formal hydrogen-bonding networks within electronically delocalized π-conjugated oligopeptide nanostructures
Wall, Brian D.,Zhou, Yuecheng,Mei, Shao,Ardoa, Herdeline Ann M.,Ferguson, Andrew L.,Tovar, John D.
, p. 11375 - 11385 (2014)
This photophysical study characterizes the generality of intermolecular electronic interactions present within nanomaterials derived from self-assembling oligopeptides with embedded π-conjugated oligophenylenevinylene (OPV) subunits stilbene and distyrylbenzene that in principle present two distinct β-sheet motifs. Two different synthetic approaches led to oligopeptides that upon self-assembly are expected to self-assemble into multimeric aggregates stabilized by β-sheet-like secondary structures. The target molecules express either two C-termini linked to the central OPV core (symmetric peptides) or the more common N-termini to C-termini polarity typical of natural oligopeptides (nonsymmetric peptides). Both peptide secondary structures were shown to form extended 1-D peptide aggregates with intimate intermolecular π-electron interactions. Differences in length of the π-conjugated OPV segments resulted in differing extents of intermolecular interactions and the resulting photophysics. The peptides containing the shorter stilbene (OPV2) units showed little ground state interactions and resulted in excimeric emission, while the longer distyrylbenzene (OPV3) peptides had different ground state interactions between adjacent π-conjugated subunits resulting in either perturbed electronic properties arising from exciton coupling or excimer-like excited states. Molecular dynamics simulations of nascent aggregate formation predict peptide dimerization to be a spontaneous process, possessing thermodynamic driving potentials in the range 2-6 kcal/mol for the four molecules considered. Antiparallel stacking of the peptides containing an OPV3 subunit is thermodynamically favored over the parallel orientation, whereas both arrangements are equally favored for the peptides containing an OPV2 subunit. This study validates the generality of peptide-π-peptide self-assembly to provide electronically delocalized supramolecular structures and suggests flexibility in peptide sequence design as a way to tune the material properties of π-conjugated supramolecular polymers.
Double-threaded dimer and supramolecular oligomer formed by stilbene modified cyclodextrin: Effect of acyl migration and photostimuli
Kanaya, Akira,Takashima, Yoshinori,Harada, Akira
experimental part, p. 492 - 499 (2011/04/15)
We observed changing supramolecular structures of stilbene-α- cyclodextrin (StiO-α-CD) by photoirradiation and migration. Stilbene derivatives show photoinduced isomerization under irradiation with λ =340 nm to give 2-cis-StiO-α-CD and with λ =254 nm to give 2-trans-StiO-α-CD. Photoisomerization of StiO-α-CD shows the photostationary state during 30 min. 2D NMR and diffusion coefficient studies revealed that 2-trans-StiO-α-CD forms a double-threaded dimer but 2-cis-StiO-α-CD changes to a supramolecular oligomer by photoirradiation. We found that the mutual migration of a stilbene group (StiO) on α-CD occurs under neutral conditions. The StiO group of α-CD (StiO-α-CD) moves between the C2 and C3 positions on the secondary hydroxyl group of StiO-α-CD (the wider rim of α-CD) to give 3-trans-StiO-α-CD. 3-trans-StiO-α-CD forms a supramolecular oligomer, whereas 3-cis-StiO-α-CD changes to a double-threaded dimer, indicating that 3-StiO-α-CDs gives the opposite results in the supramolecular structures of 2-StiO-α-CDs. The thermal isomerization (migration) is very slow. It takes about 300 h to reach the equilibrium state. Moreover, the migration rate constant (ktrans3→2) of the trans-StiO group from the C3 position to the C2 position of α-CD is faster than k trans2→3 from the C2 position to the C3 position of α-CD. On the other hand, kcis2→3 of the cis-StiO group from the C2 position to the C3 position of α-CD is faster than kcis3→2 from the C3 position to the C2 position, meaning kcis2→3 > kcis3→2, which is the opposite result for k trans3→2 > ktrans2→3. The formation of a stable double-threaded dimer would suppress the migration of the StiO group of StiO-α-CDs in aqueous solutions.
