Open Access Research article ions is generally used as a method for measuring metal complex stability constants. This technique first described by Bjerrum [1] and has been investigated extensively by numerous researches [2-7]. D.J. Perkins examined amino acid structures on the stabilities of complexes formed with metals of group II [8]. A. E. Martell and coworkers have conducted vital studies on amino acid complexes and predicted their stability constants [9-11]. The behavior of the complexes

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... different temperatures was probed by M.S. Masoud et al. [12]. Thermodynamic parameters for the formation of glycine with metal ions were investigated by S. Sammartano [13]. Formations of binary and ternary complexes were studied by M.M. Shoukry et al. [14]. Cu (II) amino acids complexes are useful antibacterial agents [15]. The stability constants of copper (II) complexes with several amino acids were calculated in dioxane-water mixtures by A. Dogan et al. [16]. The stability of binary complexes of L-aspartic acid in dioxanewater mixture was probed by R.S. Rani et al. [17]. H. Demirelli, et al. have determined the formation constants of phenylalanine complexes of Ni(II), Cu(II), and Zn(II) in water media at 25°C and µ = 0.1 mol L -1 KCl [18]. A.A. Mohamed et al. [19] have measured stability constants and thermodynamic parameters for glycine and L-threonine complexes with some rare metal ions in water. The interactions of L-glutamic and L-aspartic acid with some metal ions has been probed by S.A.A Sajadi [20]. Critical survey of formation constants of phenylalanine with metal ions has been reported by L.D. Pettit [21]. A. Eid Fazary, et al. have investigated the protonation equilibria of α-amino acids in water and dioxane mixtures [22]. The stability constants of Ni (II) with some amino acids were probed by N. Turkel [23]. Phenylalanine is a one of the few amino acids that can directly affect brain chemistry by crossing the blood-brain barrier. Phenylalanine is used to cure depression, attention deficithyperactivity disorder (ADHD), Parkinson's disease, chronic pain, osteoarthritis, rheumatoid arthritis, alcohol withdrawal symptoms, and a skin disease called vitiligo [24] . Abstract A new and simple method was developed to determine the stability constants of phenylalanine complexes of Co (II), Ni (II), Cu(II), Zn (II) and Pb (II) metal ions in water and water-dioxane mixtures at four different temperatures of 25, 37, 45 and 55°C potentiometrically using modified Bjerrum method. Ionic strength of medium was retained at 0.10 M by sodium nitrate. Our results revealed that the stability constant values are greater in water-dioxane mixtures than in water alone. The increasing trend in stability constant values in water and mixture of water-dioxane are the same as follows: K f Co (II)-Phe <K fZn (II)-Phe <K f pb (II)-Phe <K f Ni (II)-Phe <K fCu (II) -Phe Furthermore, by knowing the stability constants at different temperatures, thermodynamic parameters of ΔH°, ΔS° and ΔG° for the respective complexes were acquired. ΔH°, ΔS° values were positive. Negative ΔG° values conveyed the spontaneity of the complex formation process. Also it is found out that the stability constant of the pertinent complexes increases as the temperature rises meaning that the reactions are endothermic. Citation: Ghiamati E (2017) Thermodynamic Studies on the Interaction between Phenylalanine with Some Divalent Metal Ions in Water and Water-Dioxane Mixtures. SOJ Biochem 3(1):1-6. DOI: http://dx.Citation: Ghiamati E (2017) Thermodynamic Studies on the Interaction between Phenylalanine with Some Divalent Metal Ions in Water and Water-Dioxane Mixtures. SOJ Biochem 3(1):1-6. DOI: http://dx.