Proton Transfer and Structure-Specific Fluorescence in Hydrogen Bond-Rich Protein Structures
Kaminski, Schierle Gabriele S
Journal of the American Chemical Society
American Chemical Society
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Pinotsi, D., Grisanti, L., Mahou, P., Gebauer, R., Kaminski, C., Hassanali, A., & Kaminski, S. G. S. (2016). Proton Transfer and Structure-Specific Fluorescence in Hydrogen Bond-Rich Protein Structures. Journal of the American Chemical Society, 138 3046-3057. https://doi.org/10.1021/jacs.5b11012
Protein structures which form fibrils have recently been shown to absorb light at energies in the near UV range and to exhibit a structure-specific fluorescence in the visible range even in the absence of aromatic amino acids. However, the molecular origin of this phenomenon has so far remained elusive. Here, we combine ab initio molecular dynamics simulations and fluorescence spectroscopy to demonstrate that these intrinsically fluorescent protein fibrils are permissive to proton transfer across hydrogen bonds which can lower electron excitation energies and thereby decrease the likelihood of energy dissipation associated with conventional hydrogen bonds. The importance of proton transfer on the intrinsic fluorescence observed in protein fibrils is signified by large reductions in the fluorescence intensity upon either fully protonating, or deprotonating, the fibrils at pH = 0 or 14, respectively. Thus, our results point to the existence of a structure-specific fluorophore that does not require the presence of aromatic residues or multiple bond conjugation that characterize conventional fluorescent systems. The phenomenon may have a wide range of implications in biological systems and in the design of self-assembled functional materials.
We thank Prof. M. Sauer for useful discussions. This work was funded by grants from the Medical Research Council UK (MR/K015850/1 and MR/K02292X/1), Alzheimer Research UK (ARUKEG2012A-1), U.K. EPSRC (EP/H018301/1) and the Wellcome Trust (089703/Z/09/Z). D.P. wishes to acknowledge support from the Swiss National Science Foundation and the Wellcome Trust through personal fellowships. We thank LMB Visual Aids for graphics support.
Wellcome Trust (089703/Z/09/Z)
External DOI: https://doi.org/10.1021/jacs.5b11012
This record's URL: https://www.repository.cam.ac.uk/handle/1810/253632