Amplification of Electronic Circular Dichroism—A Tool to Follow Self-Assembly of Chiral Molecular Capsules

Abstract

Electronic circular dichroism (ECD) can be used to study various aspects of self-assembly (definition of stoichiometric ratios, chirality amplification during self-assembly, host-guest complexation). In this work, we show that ECD is a valuable tool for monitoring the self-assembly of chiral peptide-based capsules. By analyzing the signs, intensities, and temperature dependences of ECD bands, the effects of the non-specific processes can be separated from the restriction of intramolecular motion (RIM) caused by discrete self-assembly. Analysis of experimental and theoretical ECD spectra show that the differences between assembled and non-assembled species originate from induction of inherently chiral conformation and restriction of conformational freedom that leads to amplification of ECD signals during self-assembly of discrete species.

Chiral Water-Soluble Molecular Capsules With Amphiphilic Interiors

“…This trend is interpreted by gradual dissociation of the dimers to monomers at concentration < 1 mM. The explanation of this effect is based on the previous findings that correlate conformational lability and self-assembly processes with the intensity of ECD spectra ( Szymański et al, 2021 ). Monomers are expected to have higher conformational lability than the self-assembled dimers.…”

“…Concentration-dependent (L- GluR ) 2 (0.74–30 mM) indicates that the values of D reflect the size of dimeric species within the concentration range of 0.74–10 mM, and at a higher concentration the compounds start to aggregate ( Figure 2B ). To follow the process at lower concentrations, we used CD spectroscopy, which can be a sensitive probe for self-assembly ( Szymański et al, 2021 ). Concentration-dependent CD spectra of L- GluR (0.075–3.1 mM) show a gradual decrease of intensity of the bands (Δε), while the intensities of the UV bands (ε) remain unchanged ( Figures 2C–E ).…”

Molecular vessels from preorganised natural building blocks

“…88 Cavitands 23 and 24 containing polar amino acids (Gln and His) are soluble in water, DMSO, or methanol, but do not self-assemble in these competitive solvents, as proved by following their ordering by electronic circular dichroism (ECD). 89 However, dimerisation is templated by fullerenes, and the resulting dimer, e.g. ( l - 23 ) 2 ⊃C 60 (Fig.…”