New Insights on the Nature of the Chemical Species Involved during the Process of Dopamine Deprotonation in Aqueous Solution: Theoretical and Experimental Study

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• 作者：Silvia Corona-Avendañ ; o ; Georgina Alarcó ; n-Angeles ; Giselle A. Rosquete-Pina ; Alberto Rojas-Hern&aacute ; ndez ; Atilano Gutierrez ; M. Teresa Ramí ; rez-Silva ; Mario Romero-Romo ; Manuel Pa
• 刊名：Journal of Physical Chemistry B
• 出版年：2007
• 出版时间：February 22, 2007
• 年：2007
• 卷：111
• 期：7
• 页码：1640 - 1647
• 全文大小：248K
• 年卷期：v.111,no.7(February 22, 2007)
• ISSN：1520-5207

文摘

Due to dopamine's chemical structure and the fact that it has three pK_a values, its deprotonation process, inaqueous solution, may involve different chemical species. For instance, the first deprotonation step, from thefully protonated dopamine molecule (H₃DA⁺) to the neutral one (H₂DA), will result in zwitterionic speciesif a proton from one of the OH groups in the catechol ring is lost or into a neutral species if the proton is lostfrom the amino group. Given that the interaction of such a product with its environment will be quite differentdepending on its nature, it is very important, therefore, to have an accurate knowledge of which is the dopaminechemical species that results after each deprotonation step. In order to gain a better understanding of dopaminechemistry and to establish a plausible dopamine deprotonation pathway, the optimized geometries of theaforementioned species were calculated in this work by means of the density functionals theory (B3LYP/6-311+G(d,p)) in both cases: in vacuo and with solvent effect, to assess, among other theoretical criteria, theproton affinities of the different dopamine species. This permitted us to propose the following reaction pathway:Moreover, the calculations of the chemical shift (NMR-GIAO) modeling the effect of the solvent with acontinuum method (PCM) was in agreement with the ¹³C NMR experimental spectra, which confirmed evenfurther the proposed deprotonation pathway.