Document Type
Article
Publication Date
2017
Digital Object Identifier (DOI)
https://doi.org/10.1371/journal.pone.0176983
Abstract
Intrinsic protein fluorescence is inextricably linked to the near-UV autofluorescence of aromatic amino acids. Here we show that a novel deep-blue autofluorescence (dbAF), previously thought to emerge as a result of protein aggregation, is present at the level of monomeric proteins and even poly- and single amino acids. Just as its aggregation-related counterpart, this autofluorescence does not depend on aromatic residues, can be excited at the long wavelength edge of the UV and emits in the deep blue. Differences in dbAF excitation and emission peaks and intensities from proteins and single amino acids upon changes in solution conditions suggest dbAF’s sensitivity to both the chemical identity and solution environment of amino acids. Autofluorescence comparable to dbAF is emitted by carbonyl-containing organic solvents, but not those lacking the carbonyl group. This implicates the carbonyl double bonds as the likely source for the autofluorescence in all these compounds. Using beta-lactoglobulin and proline, we have measured the molar extinction coefficients and quantum yields for dbAF in the monomeric state. To establish its potential utility in monitoring protein biophysics, we show that dbAF emission undergoes a red-shift comparable in magnitude to tryptophan upon thermal denaturation of lysozyme, and that it is sensitive to quenching by acrylamide. Carbonyl dbAF therefore provides a previously neglected intrinsic optical probe for investigating the structure and dynamics of amino acids, proteins and, by extension, DNA and RNA.
Rights Information
This work is licensed under a Creative Commons Attribution 4.0 License.
Was this content written or created while at USF?
Yes
Citation / Publisher Attribution
PLoS ONE, v. 12, issue 5, art. e0176983
Scholar Commons Citation
Niyangoda, Chamani; Miti, Tatiana; Breydo, Leonid; Uversky, Vladimir; and Muschol, Martin, "Carbonyl-based Blue Autofluorescence of Proteins and Amino Acids" (2017). Molecular Medicine Faculty Publications. 290.
https://digitalcommons.usf.edu/mme_facpub/290
Supporting Information
