H. Alsamamra^#, Sawsan Abusharkh, M. Abuteir

Department of Physics, Al-Quds University, Jerusalem

Human and bovine serum albumins are the most common proteins in the circulatory system of many organisms. Numerous studies are regarding their interactions with different types of ligands. These interactions are important for their applicability in many areas in biomedical field. The interaction of human serum albumin (HSA) and bovine serum albumin (BSA) with vitamin B₁₂ was investigated using UV absorption and fluorescence spectroscopy. Results showed that the absorption and fluorescence intensities decreased as the vitamin C concentration increases. The calculated binding constant (k ~10⁴ M^–1) showed a week binding of vitamin B₁₂ with both serum albumins. The analysis of fluorescence quenching for HSA/BSA-vitamin B₁₂ interaction (k_q ~ 10¹² [L] mol^–1×s^–1, where k_q is the protein bimolecular quenching rate, and [L] represents the concentrations of the quencher) reveals the dynamic quenching process and clearly confirms the existence of static mechanism of fluorescence quenching.

Key words: Human serum albumin, bovine serum albumin, vitamin B₁₂, UV-absorption, fluorescence spectroscopy, binding constant, binding mode.

Corresponding author’s e-mail: ^#hsamamra@staff.alquds.edu

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