Native and denatured Zn cytochrome c studied by fluorescence line narrowing spectroscopy

Veronika Logovinsky, A. D. Kaposi, J. M. Vanderkooi

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20 Citations (Scopus)


Fluorescence Line Narrowing (FLN) spectroscopy was employed to compare the environment around the porphyrin in folded and unfolded Zn-substituted cytochrome c (Zn cyt c). Parameters of the resolved spectra, including the inhomogeneous energy-distribution function, vibrational energy levels, and phonon coupling, were compared for guanidine-denatured Zn cyt c and native Zn cyt c. The spectra of denatured Zn cyt c showed increased broad background and decreased peak resolution when compared to the native protein, indicating that denaturation results in increased phonon coupling. The energy-distribution function for the unfolded protein was fitted to a single Gaussian centered at 17230 cm-1 with a width of approx. 360 cm-1, which proved to be blue shifted and much wider than that for native Zn cyt c (approx. 65 cm-1). Vibrational frequencies of the ground-state for Zn cyt c were identified and shown to change upon denaturation. Temperature-dependence of the FLN spectra of native Zn cyt c was analyzed and found to have step-like broadening between 40 K and 50 K. Such discontinuous spectral broadening behavior suggests that a discrete conformational change occurs in the protein at these temperatures.

Original languageEnglish
Pages (from-to)149-160
Number of pages12
JournalBiochimica et Biophysica Acta (BBA)/Protein Structure and Molecular
Issue number2-3
Publication statusPublished - Feb 13 1993


  • Cytochrome c
  • Energy selection
  • Fluorescence line narrowing
  • Guanidine hydrochloride
  • Inhomogeneous broadening
  • Protein denaturation

ASJC Scopus subject areas

  • Biophysics
  • Structural Biology
  • Biochemistry
  • Molecular Biology

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