Thermodynamics of binding of Zn2+ to carbonic anhydrase inhibitors |
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Authors: | MILAN REMKO VLADIMÍR GARAJ |
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Affiliation: | Department of Pharmaceutical Chemistry , Comenius University , Odbojarov 10, SK-832 32, Bratislava, Slovakia |
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Abstract: | The Becke3LYP functional of DFT theory and the two-layered ONIOM (B3LYP/6–311 + G(d,p): MNDO) method were used to characterize 46 gas-phase complexes of 34 neutral and anionic ligands (H2O, CH3OH, CH3COOH, CH3CONH2, HOSO2NH2, CO2, HSO2NH2, CH3SO2NH2, CH3C(= O)NHOH, imidazole, NH2SO2NH2, anions of 4-aminobenzenesulphonamide, saccharin, 1I9L, brinzolamide, dorzolamide, acetazolamide, further HO(?), CH3CO(?), CH3COO(?), CH3CONH(?), N = N = N(?), S = C = N(?), CH3C(= O)NHO(?), HOCOO(?), imidazoleN(?), phenol-O(?), HOSO2NH(?), (?)OSO2NH(?), (?)OSO2NH2, H2NSO2NH(?), HSO2NH(?), CH3SO2NH(?), and CF3SO2NH(?), respectively) with Zn2+. Proton dissociation enthalpies and Gibbs energies of acidic inhibitors in the presence of zinc were computed. Their gas-phase acidity considerably increases upon chelation. Of the bases investigated, the weakest zinc affinity is exhibited by carbon dioxide (- 313.5 kJ mol?1). Deprotonated inhibitors have higher affinities for zinc than the neutral ones. Compared to the other mono-deprotonated ligands the acetohydroxamic acid anion has the highest affinity for zinc (- 1872.7 kJ mol?1). The zinc affinity of the acetazolamide anion computed using the hybrid ONIOM (B3LYP/6-311 + G(d,p): MNDO) method is in very good agreement with the full DFT ones and this method can be adopted to model large complexes of inhibitors with the active site of carbonic anhydrase. |
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