G. DAMIAN*, SIMONA CAVALU**, V. MICLĂUŞ***, LAVINIA SABĂU****, NICOLETA VEDEANU*****, C.M. LUCACIU*****
*Department of Biomedical Physics, Faculty of Physics, “Babeş-Bolyai” University, RO-400084, Cluj-Napoca, Romania, dgrig@phys.ubbcluj.ro
**Department of Biophysics, Faculty of Medicine and Pharmaceutics, University of Oradea, RO-410087, Oradea, Romania
***Faculty of Chemistry and Chemical Engineering, “Babeş-Bolyai” University, RO-400084, Cluj-Napoca, Romania
****Department of Physiology, Faculty of Medicine, “Iuliu Haţieganu” University of Medicine and Pharmaceutics, RO-400023, Cluj-Napoca, Romania
*****Department of Physics-Biophysics, Faculty of Pharmacy, “Iuliu Haţieganu” University of Medicine and Pharmaceutics, RO-400023, Cluj-Napoca, Romania
Abstract. Conformational changes and interaction of spin label with cytochrome c protein at different pH value have been studied by FT-IR and EPR spectroscopy. Electron Paramagnetic Resonance (EPR) spectroscopy was used to investigate the mobility of Tempo spin label (3-carbamoyl-2,2,5,5-tetramethyl-3-pyrrolin-1-yloxy) in order to obtain useful information related to the interaction between the nitroxide group and the functional site of the lyophilized protein samples. A minimum mobility can be observed around the isoelectric point (pHi = 9.8). The best information from infrared protein spectra is obtained in the amide I band which appears between 1700 and 1600 cm–1. The results of qualitative and quantitative analysis by curve fitting to the inverted second derivative spectra of amide I features of lyophilized hemoglobin reveal a decrease in β-sheet content as the pH values increases and a decrease in α-helix content at lower or higher pH values as well as a decrease in turns content
Key words: EPR, FT-IR, spin label, cytochrome c.
Corresponding author’s e-mail: dgrig@phys.ubbcluj.ro
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