Kreiser, T. | Search bioRxiv

bioRxiv2021

Inulin nanostructures: The sweet-spot of carbohydrate self-assembly

Supramolecular architecture formation by the self-assembly of proteins and nucleic acids is well studied. Yet, the spontaneous organization of oligosaccharides, the most common polymers in nature, is less explored. Here, using inulin as a model, we identify the "sweet spot" length for oligosaccharide assembly. Inulin forms discrete spheres in a concentration-dependent manner. Size-based fractionation displayed markedly different aggregation morphologies. Based on these findings, we believe that carbohydrates could become an important source for novel self-assembling materials.

biophysics↗

bioRxiv2021

On-off transition and ultrafast decay of amino acid luminescence driven by modulation of supramolecular packing

It has been experimentally observed that various biomolecules exhibit clear luminescence in the visible upon aggregation, contrary their monomeric state. However, the physical basis for this phenomenon is still elusive. Here, we systematically examine all coded amino acids to provide non-biased insights into this phenomenon. Several amino acids, including non-aromatic, show intense visible luminescence. While lysine crystals display the highest signal, the very chemically similar non-coded ornithine does not, implying a role for molecular packing rather than the chemical characteristics of the molecule. Furthermore, cysteine show luminescence that is indeed crystal-packing-dependent as repeated rearrangements between two crystal structures result in a reversible on-off optical transition. In addition, ultrafast lifetime decay is experimentally validated, corroborating a recently raised hypothesis regarding the governing role of n{pi}* states in the emission formation. Collectively, our study supports the hypothesis that electronic interactions between molecules that are non-fluorescent and non-absorbing at the monomeric state may result in reversible optically-active states by the formation of supramolecular fluorophores.

biophysics↗