The interaction of iodine with bovine serum albumin (BSA) in dimethylsulfoxide (DMSO) aqueous solutions was studied by means of fluorescence and UV/Vis absorption spectroscopy methods. Physicochemical peculiarities of these solutions were revealed. The results showed that the tri-iodide ion formed in the 1DMSO？:？2H2O solution caused the fluorescence quenching of BSA. The modified Stern-Volmer quenching constant and corresponding thermodynamic parameters, the free energy change ( ), enthalpy change ( ), and entropy change ( ), at different temperatures (293, 298, and 303？K) were calculated, which indicated that the hydrophobic and electrostatic interactions were the predominant operating forces. The binding locality distance r between BSA and tri-iodide ion at different temperatures was determined based on F？rster nonradiation fluorescence energy transfer theory. 1. Introduction Iodine is an element that is needed for the production of the most important organoiodine compounds for human health thyroid hormones: thyroxine (T4) and triiodothyronine (T3). Without sufficient iodine, body is unable to synthesize these hormones and play a role in virtually all physiological functions. T4 is transported in blood, being protein-bound, principally to globulin, transthyretin, and serum albumin [1]. The absorption of inorganic-iodine, such as , is certainly bound to serum albumin. Serum albumins, human serum albumin (HSA), and bovine serum albumin (BSA) play an important role in the transport and disposition of a wide variety of substances like metals, fatty acids, amino acids, hormones, and drugs [2–6]. Competitive interactions in the aqueous solutions containing DMSO and ions were a subject of numerous studies [7, 8]. In this paper, the interaction of iodine with BSA in DMSO aqueous solutions was studied at different temperatures by using fluorescence and UV/Vis spectroscopy methods. The binding constants and the binding locality distance are calculated, and the thermodynamic parameters of the process are proposed. 2. Methodology The materials used are as follows. BSA and DMSO were purchased from Sigma Chemical Company (USA). Iodine was purified by sublimation. Doubly distilled water was used for the preparation of binary mixtures of 1DMSO？:？2H2O. BSA concentration was 0.4？mg/mL, determined by electron absorption spectra in the UV region using a molar absorption coefficient ？M？1？cm？1 ( ？nm) [9]. The methods applied are the following. To perform the UV/Vis absorption measurements, we apply the following. The absorption spectra of iodine in 1DMSO？:？2H2O solutions
References
[1]
G. W. Gribble, “Naturally occurring organohalogen compounds—a comprehensive survey,” Progress in the Chemistry of Organic Natural Products, vol. 68, pp. 1–423, 1996.
[2]
K. Grigoryan and A. Ghazaryan, “Characterization of the platinum (II) dimethylsulfoxide complex binding to bovine serum albumin by fluorescence spectroscopy method,” Global Journal of Analytical Chemistry, vol. 3, pp. 1–8, 2012.
[3]
K. R. Grigoryan, M. G. Aznauryan, N. A. Bagramyan, L. G. Gevorkyan, and S. A. Markaryan, “Spectroscopic determination of binding between human serum albumin and a platinum(II) dimethylsulfoxide complex,” Journal of Applied Spectroscopy, vol. 75, no. 4, pp. 593–596, 2008.
[4]
S. Cui, X. Hu, and J. Liu, “Study of the binding of herbacetin to bovine serum albumin by fluorescence spectroscopy,” Journal of Solution Chemistry, vol. 40, no. 5, pp. 764–774, 2011.
[5]
Y. Z. Zhang, B. Zhou, Y. X. Liu, C. X. Zhou, X. L. Ding, and Y. Liu, “Fluorescence study on the interaction of bovine serum albumin with P-aminoazobenzene,” Journal of Fluorescence, vol. 18, no. 1, pp. 109–118, 2008.
[6]
H. Xu, Q. Liu, Y. Zuo, Y. Bi, and S. Gao, “Spectroscopic studies on the interaction of vitamin C with bovine serum albumin,” Journal of Solution Chemistry, vol. 38, no. 1, pp. 15–25, 2009.
[7]
K. R. Grigoryan and A. A. Shiladzhyan, “The effect of solvated ions on the thermal denaturation of human serum albumin in water-dimethylsulfoxide solutions,” Russian Journal of Bioorganic Chemistry, vol. 35, no. 5, pp. 581–584, 2009.
[8]
S. Markarian, K. Grigoryan, and R. Harutunyan, “Physicochemical properties of CuCl2, Cu(NO3)2 and Al(NO3)3 dimethylsulfoxide and dimethylsulfoxide-water solutions,” Russian Journal of Physical Chemistry, vol. 69, pp. 990–993, 1995.
[9]
A. K. Singh and M. Darshi, “A fluorescence study of (4-{(1E,3E)-4-[4-(dimethylamino)phenyl]-buta-1,3-dienyl}phenyl)methanol and its bioconjugates with bovine and human serum albumins,” New Journal of Chemistry, vol. 28, no. 1, pp. 120–126, 2004.
[10]
Y. J. Wei, C. G. Liu, and L. P. Mo, “Ultraviolet absorption spectra of iodine, iodide ion and triiodide ion,” Spectroscopy and Spectral Analysis, vol. 25, no. 1, pp. 86–88, 2005, Article in Chinese, Abstract in English.
[11]
S. Markarian, R. Harutunyan, V. Grigoryan, and N. Beyleryan, “Physicochemical properties of Dialkylsulfoxide Aqueous and CCl4 solutions,” Chem. Chem.Techn., vol. 28, pp. 18–22, 1985 (Russian).
[12]
D. Martin and H. G. Hauthal, Dimethylsulfoxide, Van Nostrand Reinhold, Workingham, Berkshire, UK, 1975.
[13]
J. R. Lakowicz, Principles of Fluorescence Spectroscopy, Springer, New York, NY, USA, 3rd edition, 2006.
[14]
J. R. Lakowicz and G. Weber, “Quenching of fluorescence by oxygen. A probe for structural fluctuations in macromolecules,” Biochemistry, vol. 12, no. 21, pp. 4161–4170, 1973.
[15]
R. Punith, A. H. Hegde, and S. Jaldappagari, “Binding of an anti-inflammatory drug lornoxicam with blood proteins: insights from spectroscopic investigations,” Journal of Fluorescence, vol. 21, pp. 487–495, 2011.
