title: A computational study on how structure influences the optical properties in model crystal structures of amyloid fibrils.
abstract: Amyloid fibrils have been shown to have peculiar optical properties since they can exhibit fluorescence in the absence of aromatic residues. In a recent study, we have shown that proton transfer (PT) events along hydrogen bonds (HBs) are coupled to absorption in the near UV range. Here, we gain more insights into the different types of hydrogen bonding interactions that occur in our model systems and the molecular factors that control the susceptibility of the protons to undergo PT and how this couples to the optical properties. In the case of the strong N-C termini interactions, a nearby methionine residue stabilizes the non-zwitterionic NH2-COOH pair, while zwitterionic NH3+-COO- is stabilized by the proximity of nearby crystallographic water molecules. Proton motion along the hydrogen bonds in the fibril is intimately coupled to the compression of the heavier atoms, similar to what is observed in bulk water. Small changes in the compression of the hydrogen bonds in the protein can lead to significant changes in both the ground and excited state potential energy surfaces associated with PT. Finally, we also reinforce the importance of nuclear quantum fluctuations of protons in the HBs of the amyloid proteins.
authors.affiliation: International Centre for Theoretical Physics, Strada Costiera 11, Trieste 34151, Italy. ahassana@ictp.it luca.grisanti@gmail.com.
authors.forename: Luca
authors.identifier: http://orcid.org/0000-0003-4311-4676
authors.initials: L
authors.lastname: Grisanti
authors.affiliation: Department of Chemical Engineering and Biotechnology, University of Cambridge, Pembroke Street, Cambridge CB2 3RA, UK.
authors.forename: Dorothea
authors.initials: D
authors.lastname: Pinotsi
authors.affiliation: International Centre for Theoretical Physics, Strada Costiera 11, Trieste 34151, Italy. ahassana@ictp.it luca.grisanti@gmail.com.
authors.forename: Ralph
authors.initials: R
authors.lastname: Gebauer
authors.affiliation: Department of Chemical Engineering and Biotechnology, University of Cambridge, Pembroke Street, Cambridge CB2 3RA, UK.
authors.forename: Gabriele S
authors.initials: GS
authors.lastname: Kaminski Schierle
authors.affiliation: International Centre for Theoretical Physics, Strada Costiera 11, Trieste 34151, Italy. ahassana@ictp.it luca.grisanti@gmail.com.
authors.forename: Ali A
authors.initials: AA
authors.lastname: Hassanali
mesh_terms: D000682:Amyloid / Q000737:chemistry* / Q000378:metabolism; D003460:Crystallization; D006860:Hydrogen Bonding; D008956:Models, Chemical; D008958:Models, Molecular; D055620:Optical Phenomena; D011522:Protons
chemical_list: D000682:Amyloid; D011522:Protons