Low energy optical excitations as an indicator of structural changes initiated at the termini of amyloid proteins

Jong, Kwang Hyok; Azar, Yavar T.; Grisanti, Luca; Stephens, Amberley D.; Jones, Saul T. E.; Credgington, Dan; Schierle, Gabriele S Kaminski; Hassanali, Ali

doi:10.1039/c9cp04648h

Cited by 19 publications

(35 citation statements)

References 45 publications

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“…We next investigated whether the above structures also display fluorescence excitation and emission properties as has been observed for amyloid-like structures reported previously (5,40,41). Fig.…”

Section: Resultsmentioning

confidence: 65%

“…The more glutamine residues in the poly-glutamine polymer, the faster the aggregation propensity of the polypeptide chain. This led us to investigate whether L-glu on its own under conditions which normally promote fibril formation, such as an increase in temperature (14), was able to form structures with similar optical properties, as recently observed for amyloid fibrils (5, 29, 30).…”

Section: Resultsmentioning

confidence: 82%

“…We next compared the experimental absorption spectra of L-glu, L-pyro and L-pyro-amm with the ones obtained from time dependent density functional theory (TDDFT). We highlight here, that the small size of the systems permitted us to determine the spectra using a hybrid functional, thereby not only advancing the quality of our theoretical predictions from previous studies (5,40,41) but also coupling the optical properties directly to different vibrational modes.…”

Section: Resultsmentioning

confidence: 89%

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Short hydrogen bonds enhance non-aromatic protein-related fluorescence

Stephens

Qaisrani

Ruggiero

et al. 2020

Preprint

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Disentangling the origin of the optical activity of non-aromatic proteins is challenging due to their size and thus their high computational requisites. Here we show, in a much smaller model system, that the single amino acid glutamine undergoes a chemical transformation leading to an unreported glutamine-like structure which has a similar broad absorption spectrum reported previously for non-aromatic proteins. We further show computationally that the optical activity of the glutamine-like structure is directly coupled to short-hydrogen bonds, but also displays charge and vibrational fluctuations, the latter of which are also present in less optically active structures such as in L-glutamine. Since experimentally the glutamine-like structure is the brightest structure, we conclude that short-hydrogen bonds are the ones responsible for the large Stokes shift observed in optically active non-aromatic proteins.

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Section: Resultsmentioning

confidence: 65%

Section: Resultsmentioning

confidence: 82%

Section: Resultsmentioning

confidence: 89%

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Short hydrogen bonds enhance non-aromatic protein-related fluorescence

Stephens

Qaisrani

Ruggiero

et al. 2020

Preprint

Self Cite

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“…It was suggested that the hydrogen bonds and, in specific cases, the aromatic stacking, can underlie these optical properties. 1,20 Yet, other views have suggested impurities and oxidation as alternative mechanisms, ascribing no significant role to the molecular arrangement. 21 Indeed, oxidation of aromatic moieties is known to result in the formation of fluorescent products.…”

Section: Introductionmentioning

confidence: 99%

“…However, this cannot readily explain the emergence of intrinsic fluorescence upon aggregation of non-aromatic species. 6,19,20 Overall, the key evidence to distinguish between these options and elucidate the mechanism of intrinsic fluorescence upon aggregation was so far missing. We believe that the reversible transitions between the luminescent and non-luminescent states upon controllable change of aggregate structure is such an evidence.…”

Section: Introductionmentioning

confidence: 99%

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

Arnon

Kreiser

Yakimov

et al. 2021

Preprint

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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 nπ* 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.

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Intrinsic Luminescence from Nonaromatic Biomolecules

2020

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Novel emitters that do not contain traditional chromophores but only electron-rich moieties (e. g. amine, C=O, À OH, ether, and imide), which are classified as nonconventional luminophores, have been more frequently reported. Although more and more examples have been demonstrated, their emission mechanism remains unclear. The clustering-triggered emission (CTE) mechanism has previously been proposed to rationalize the luminescence of unconventional chromophores. Moreover, great attention has been paid to the distinctive inherent luminescence from nonaromatic biomolecules such as cellulose, starch, sugars, and nonaromatic amino acids and proteins. In this Review, we summarize these unconventional biomolecular luminophores and apply the CTE mechanism to rationalize such a phenomenon. This Review may shed new light on the understanding of intrinsic emission of nonaromatic biomolecules and decipher the intrinsic fluorescence from cells and tissues.

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Low energy optical excitations as an indicator of structural changes initiated at the termini of amyloid proteins

Abstract: We study the optical properties of amyloid aggregates relevant for neurodegenerative disease using experiments and computation. The low energy optical absorption in the near-UV range depends on conformations and involves charge-transfer excitations.

Cited by 19 publications

References 45 publications

Short hydrogen bonds enhance non-aromatic protein-related fluorescence

Short hydrogen bonds enhance non-aromatic protein-related fluorescence

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

Intrinsic Luminescence from Nonaromatic Biomolecules

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