Proton NMR relaxation in albumin solutions doped with Mn(II) |
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Authors: | Ali Yilmaz M. Z. Koylu E. Uysal |
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Affiliation: | (1) Department of Physics, Faculty of Science, University of Dicle, 21280 Diyarbakir, Turkey;(2) Division of Statistics, Professional High School, University of Dicle, Diyarbakir, Turkey |
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Abstract: | The aim of this study is to obtain further information about the source of proton relaxation in the Mn(II)-human serum albumin complex. For this purpose, proton relaxation rates in albumin solutions 1/T 1 and 1/T 2 were measured versus increasing amounts of manganese [Mnt]. The fractions of manganese bound to albumin [Mnb] and free manganese [Mnf] were then determined from proton relaxation rate enhancement data. Paramagnetic contributions of bound manganese to the observed relaxation rates (1/T 1p*)b and (1/T 2p*)b were also determined. Finally, the (1/T 2p*)b/(1/T 1p*)b ratio was used in a derived equation to estimate an effective correlation time τ. Mean τ value of the complex was found to be in the order of 3 ns, while the hydration number of bound manganese q was estimated to be about 4. The 1/τ was found to be the sum of the inverse values of rotational correlation time 1/τ r, mean residence time of water in hydration spheres of the complex 1/τ m, and longitudinal electronic relaxation time of manganese 1/τ s in the complex. In conclusion, the relaxation mechanism in albumin solutions containing Mn(II) can be interpreted through dipolar and scalar interactions modulated by τ r, τ m and τ s. This analysis enables one to get reasonable figures for the τ r and q of Mn(II) in albumin solution. |
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