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Equilibrium, stopped flow, and temperature-jump spectrophotometry have been used to identify processes in the unfolding of ferricytochrome c in acidic aqueous solutions. A relaxation occurring in approximately 100 microseconds involves perturbation of a spin-equilibrium between two folded conformers of the protein with methionine-80 coordinated or dissociated from the heme iron. The protein unfolds more slowly, in milliseconds, with dissociation and protonation of histidine-18. These two transitions appear cooperative in equilibrium measurements at low (0.01 M) ionic strength, but are separated at higher (0.10 M) ionic strength. They are resolved under both conditions in the dynamic measurements. The spin-equilibrium description permits a unified explanation of a number of properties of ferricytochrome c in acidic aqueous solutions.
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ACS Omega
January 2019
Department of Chemistry, Drexel University, 3141 Chestnut Street, Philadelphia, Pennsylvania 19104, United States.
Fluorescence, visible circular dichroism (CD), absorption, and resonance Raman spectroscopy techniques were combined to explore structural changes of ferricytochrome upon its binding to cardiolipin-containing liposomes (20% 1,1',1,2'-tetraoleyolcardiolipin and 1,2-deoleyol--glycero-3-phosphocholine) at acidic pH (6.5). According to the earlier work of Kawai [J.
View Article and Find Full Text PDFJ Phys Chem Lett
May 2017
Department of Chemistry, Drexel University, Philadelphia, Pennsylvania 19104, United States.
The conformational changes of ferricytochrome c upon binding to cardiolipin-containing small unilamellar vesicles were studied at slightly acidic pH using fluorescence, visible circular dichroism, UV-visible absorption, and resonance Raman spectroscopy. The obtained spectroscopic response data suggest a mode of interaction, which is clearly distinct from the binding process observed at neutral pH. Evidence of a reversible and electrostatic binding mechanism under these conditions is provided through binding inhibition in the presence of 150 mM NaCl.
View Article and Find Full Text PDFBiophys Chem
March 2016
Department of Biochemistry, P.J. Šafárik University, Moyzesova 11, 040 01 Košice, Slovakia; Centre for Interdisciplinary Biosciences, P.J. Šafárik University, Jesenná 5, 040 01 Košice, Slovakia. Electronic address:
Thermal denaturation of ferricytochrome c (cyt c) has been methodically studied by absorbance, fluorescence, circular dichroism spectroscopy, viscosimetry and differential scanning calorimetry in pH range from pH 3.5 to 7.5.
View Article and Find Full Text PDFArch Biochem Biophys
December 2012
School of Chemistry, University of Hyderabad, Hyderabad 500 046, India.
Tuning of both hydrophobic and electrostatic interactions is thought to be important for the initial nucleation and stability of protein aggregates that self-assemble to produce amyloid fibrils. Importance of a critical balance of these two interactions has indeed been determined under various solution conditions of fibrillation, the acidic pH, in particular. To find out if fibrillar protein structures could be obtained under extreme alkaline conditions, cytochrome c was allowed to fibrillate in 0.
View Article and Find Full Text PDFBiophys Chem
March 2010
Department of Physical and Astronomical Sciences, University of Palermo, Via Archirafi 36, I-90123 Palermo, Italy.
We have investigated the heterogeneity of the Fe(III)-Met80 linkage of horse heart ferricytochrome c by probing the 695nm charge transfer band with absorption and electronic circular dichroism (ECD) spectroscopy. In order to verify the connection between conformational substates of the Fe(III)-Met80 linkage and the 695nm band spectral heterogeneity, we have performed experiments as a function of pH (neutral and acidic) and temperature (room and 20K). At room temperature, the ECD spectrum is blue shifted with respect to the absorption one; the shift is more pronounced at acidic pH and is compatible with the presence of sub-bands.
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