Experimental and Quantum Chemical Modeling Studies of the Interactions of l-Phenylalanine with Divalent Transition Metal Cations
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- 作者：Shilpi Mandal ; Gunajyoti Das ; Hassan Askari
- 刊名：Journal of Chemical Information and Modeling
- 出版年：2014
- 出版时间：September 22, 2014
- 年：2014
- 卷：54
- 期：9
- 页码：2524-2535
- 全文大小：413K
- ISSN：1549-960X
文摘
Encoded by the UUU and UUC codons of the genetic code, l-phenylalanine (LPA) serves as an important precursor for tyrosine and various other compounds that are necessary to support life on earth. Here, we report the synthesis (both in solid and solvent phases) and characterization of the Ni2+, Cu2+, and Zn2+ complexes of LPA by several analytical, spectral, thermal, and electrochemical techniques. The results reveal that the products formed by following the two synthetic approaches are the same, and the metal ions bind to the LPA molecules in a 1:2 molar ratio (M+2/LPA). Complementary geometries of the metal complexes are modeled involving the most predominant LPA conformers predicted at the MP2/6-311++G(d,p) level. The gaseous and aqueous phase interaction enthalpies and free energies; theoretical IR and UV鈥搗is spectra; HOMO鈥揕UMO energy gaps; dipole moments; Wiberg bond indices as well as the partial atomic charges in LPA and its metallic complexes are calculated and evaluated using B3LYP/6-311++G(d,p) as the main computational method. This study also incorporates analyses on the efficacy of the DFT-D2 level in describing dispersion contributions, performance of the BHandHLYP functional for the open-shell Cu2+-LPA system, and relative metal binding affinities of the singlet versus triplet states of the Ni2+-LPA complex. Metal鈭捪€ interactions established via the aromatic side chain of LPA add to the thermodynamic stability of the complexes, whereas metal coordination induces considerable intrinsic structural rearrangements in the molecular geometry of LPA. The LPA binding affinity order of the three Lewis acids investigated emerges as Cu2+ > Ni2+ > Zn2+, paralleling the Irving鈥揥illiams series. The illustrative evidence offered by the present work suggests that the B3LYP/6-311++G(d,p) level in combination with an empirical dispersion-correction term performs well in describing the vibrational frequencies and cation鈭捪€ interactions, which are undoubtedly of immense significance for natural sciences.