|
iDEA: Drexel E-repository and Archives >
Drexel Academic Community >
College of Arts and Sciences >
Department of Chemistry >
Faculty Research and Publications (Chemistry) >
Optical band splitting and electronic perturbations of the heme chromophore in cytochrome c at room temperature probed by visible electronic circular dichroism spectroscopy
Please use this identifier to cite or link to this item:
http://hdl.handle.net/1860/1632
|
| Title: | Optical band splitting and electronic perturbations of the heme chromophore in cytochrome c at room temperature probed by visible electronic circular dichroism spectroscopy |
| Authors: | Dragomir, Isabelle
Hagarman, Andrew
Wallace, Carmichael
Schweitzer-Stenner, Reinhard |
| Issue Date: | Feb-2007 |
| Publisher: | Biophysical Society |
| Citation: | Biophysical Journal, 92(3): pp. 989-998. |
| Abstract: | We have measured the electronic circular dichroism (ECD) of the ferri- and ferro-states of several natural
cytochrome c derivatives (horse heart, chicken, bovine, and yeast) and the Y67F mutant of yeast in the region between 300 and
750 nm. Thus, we recorded the ECD of the B- and Q-band region as well as the charge-transfer band at ;695 nm. The B-band
region of the ferri-state displays a nearly symmetric couplet at the B0-position that overlaps with a couplet 790 cm1 higher in
energy, which we assigned to a vibronic side-band transition. For the ferro-state, the couplet is greatly reduced, but still detectable.
The B-band region is dominated by a positive Cotton effect at energies lower than B0 that is attributed to a magnetically
allowed iron/heme charge-transfer transition as earlier observed for nitrosyl myoglobin and hemoglobin. The Q-band region of
the ferri-state is poorly resolved, but displays a pronounced positive signal at higher wavenumbers. This must result from a
magnetically allowed transition, possibly from the methionine ligand to the dxy-hole of Fe31. For the ferro-state, the spectra
resolve the vibronic structure of the Qv-band. A more detailed spectral analysis reveals that the positively biased spectrum can
be understood as a superposition of asymmetric couplets of split Q0 and Qv-states. Substantial qualitative and quantitative differences
between the respective B-state and Q-state ECD spectra of yeast and horse heart cytochrome c can clearly be
attributed to the reduced band splitting in the former, which results from a less heterogeneous internal electric field. Finally, we
investigated the charge-transfer band at 695 nm in the ferri-state spectrum and found that it is composed of at least three bands,
which are assignable to different taxonomic substates. The respective subbands differ somewhat with respect to their Kuhn
anisotropy ratio and their intensity ratios are different for horse and yeast cytochrome c. Our data therefore suggests different
substate populations for these proteins, which is most likely assignable to a structural heterogeneity of the distal Fe-M80
coordination of the heme chromophore. |
| URI: | http://dx.doi.org/10.1529/biophysj.106.095976
http://hdl.handle.net/1860/1632 |
| Appears in Collections: | Faculty Research and Publications (Chemistry)
|
Items in iDEA are protected by copyright, with all rights reserved, unless otherwise indicated.
|
www.drexel.edu
