UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS

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2024-11-22 1:32

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Conference: Bucharest University Faculty of Physics 2015 Meeting


Section: Biophysics; Medical Physics


Title:
Characterization of some physico-chemical properties and interactions of human and bovine serum albumin with mitomycin C


Authors:
Cristina CÎRJAN, Claudia G. CHILOM, Doina M. GĂZDARU, A. I. POPESCU


Affiliation:
Department of Electricity, Solid Physics and Biophysics, Faculty of Physics,

University of Bucharest, ROMANIA



E-mail
claudiafir@gmail.com


Keywords:
denaturation, static quenching, hydrophobic interactions, hydrogen bonding


Abstract:
In the medical field a special interest is given both to the interactions and transport mechanisms of cytostatics by serum albumins. One of these substances is mitomycin C (MMC), a natural antibiotic, with a very good antitumour activity and weak toxicity. This work aims to investigate some of the physico-chemical properties and molecular interactions of human (HSA) and bovine (BSA) serum albumins with MMC, and also to study the thermodynamic stability of the albumin complexes with MMC. The binding mechanism of MMC to BSA and HSA have been followed by UV absorption spectroscopy and steady-state fluorescence. The pH and temperature influence on the complexes of MMC with BSA and HSA was also investigated by steady-state fluorescence. The absorption of serum albumin chromophores is greater at acidic pH than at basic values, for both albumins in complexes with MMC. This could be due to the spontaneous activation of MMC at acidic pH. Thermal denaturation of BSA-MMC and HSA-MMC complexes shows that the stability of HSA-MMC complex is maintained until higher temperatures than those of BSA-MMC complex. The mechanism of MMC binding to BSA and HSA, investigated by Stern-Volmer equation, revealed that both the Stern-Volmer constant and the biomolecular quenching rate constant decrease with temperature increase. This result indicates that MMC is a static quencher. Fluorescence spectra were also used to study the interaction of BSA and HSA with MMC. Affinity constant (Ka) and the stoichiometry (n), were calculated from Scatchard plots, using the double logarithmic representation. The thermodynamic parameters (ΔG, ΔH, ΔS) were also determined, showing spontaneous and exothermic reactions (ΔG < 0, ΔH < 0) and a strong contribution of the hydrophobic interactions and hydrogen bonding (ΔS > 0, ΔH < 0) on the complex formation.