Aromatic Cluster Sensor of Protein Folding: Near-UV Electronic Circular Dichroism Bands Assigned to Fold Compactness

Viktor Farkas, Imre Jákli, Gábor K. Tóth, András Perczel

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3 Citations (Scopus)


Both far- and near-UV electronic circular dichroism (ECD) spectra have bands sensitive to thermal unfolding of Trp and Tyr residues containing proteins. Beside spectral changes at 222 nm reporting secondary structural variations (far-UV range), Lbbands (near-UV range) are applicable as 3D-fold sensors of protein's core structure. In this study we show that both Lb(Tyr) and Lb(Trp) ECD bands could be used as sensors of fold compactness. ECD is a relative method and thus requires NMR referencing and cross-validation, also provided here. The ensemble of 204 ECD spectra of Trp-cage miniproteins is analysed as a training set for “calibrating” Trp↔Tyr folded systems of known NMR structure. While in the far-UV ECD spectra changes are linear as a function of the temperature, near-UV ECD data indicate a non-linear and thus, cooperative unfolding mechanism of these proteins. Ensemble of ECD spectra deconvoluted gives both conformational weights and insight to a protein folding↔unfolding mechanism. We found that the Lb293band is reporting on the 3D-structure compactness. In addition, the pure near-UV ECD spectrum of the unfolded state is described here for the first time. Thus, ECD folding information now validated can be applied with confidence in a large thermal window (5≤T≤85 °C) compared to NMR for studying the unfolding of Trp↔Tyr residue pairs. In conclusion, folding propensities of important proteins (RNA polymerase II, ubiquitin protein ligase, tryptase-inhibitor etc.) can now be analysed with higher confidence.

Original languageEnglish
Pages (from-to)13871-13883
Number of pages13
JournalChemistry - A European Journal
Issue number39
Publication statusPublished - Jan 1 2016



  • Electronic circular dichroism spectra
  • Trp–Tyr interacting residues
  • folding intermediates
  • sensors
  • thermal unfolding

ASJC Scopus subject areas

  • Catalysis
  • Organic Chemistry

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