Binding Modes of Quinuclidinium Esters to Butyrylcholinesterase

The orientations of chiral quinuclidin-3-ol esters and benzoylcholine in the active site of horse butyrylcholinesterase have been investigated by flexible ligand docking. Change of the esters\u27 acyl moiety as well as the substituent at the quinuclidinium nitrogen atom affected the activity and stereoselectivity of the biotransformations. Analysis of interactions in the active site revealed the most important binding pat-terns for enantiomers, which define their reactivity. Calculated Gibbs energies of binding obtained by mo-lecular docking simulations were well correlated to the experimentally determined binding affinities of the investigated chiral esters. (doi: 10.5562/cca2060

Structural Basis for Selectivity of Butyrylcholinesterase towards Enantiomeric Quinuclidin-3-yl Benzoates: a Quantum Chemical Study

In order to explain different rates of hydrolysis of (R)- and (S)-quinuclidin-3-yl benzoates and benzoylcholine catalyzed with butyrylcholinesterase, semiempirical PM3 calculations were performed with an assumed active site model of human BChE (20 amino acids). Contributions of different protein residues to the stabilization of Michaelis complexes and tetrahedral intermediates were analyzed. It was shown that the hydrolysis rates of quinuclidinium enantiomers were to an appreciable extent affected by the existence or absence of the hydrogen bond between the quinuclidinium N+–H group and the protein residues. Calculations indicated that the better stabilization of quinuclidinium moiety in the Michaelis complex than in the tetrahedral intermediate was the main reason for a greater barrier and a slower reaction rate of the (R)-enantiomer of quinuclidinium esters compared to benzoylcholine. In the case of (S)-enantiomer, the calculation indicated that the barrier to the substrate reorientation from a favourable, but non-productive binding to a productive one significantly influenced the rate of hydrolysis

Structural Basis for Selectivity of Butyrylcholinesterase towards Enantiomeric Quinuclidin-3-yl Benzoates: a Quantum Chemical Study

In order to explain different rates of hydrolysis of (R)- and (S)-quinuclidin-3-yl benzoates and benzoylcholine catalyzed with butyrylcholinesterase, semiempirical PM3 calculations were performed with an assumed active site model of human BChE (20 amino acids). Contributions of different protein residues to the stabilization of Michaelis complexes and tetrahedral intermediates were analyzed. It was shown that the hydrolysis rates of quinuclidinium enantiomers were to an appreciable extent affected by the existence or absence of the hydrogen bond between the quinuclidinium N+–H group and the protein residues. Calculations indicated that the better stabilization of quinuclidinium moiety in the Michaelis complex than in the tetrahedral intermediate was the main reason for a greater barrier and a slower reaction rate of the (R)-enantiomer of quinuclidinium esters compared to benzoylcholine. In the case of (S)-enantiomer, the calculation indicated that the barrier to the substrate reorientation from a favourable, but non-productive binding to a productive one significantly influenced the rate of hydrolysis

Chemometric Analysis of Croatian Extra Virgin Olive Oils from Central Dalmatia Region

Extra virgin olive oil samples were collected from different geographical areas of Central Dalmatia region in Croatia including locations both on the coast and islands. This set included 41 oils of cul-tivar Oblica, 1 per cultivars Coratina and Leccino, and 5 of mixed cultivars Lastovka and Oblica. Attenuated total reflectance (ATR) spectra of non-treated samples were recorded and principal component analysis (PCA) was carried out on a set of obtained spectra, as well as their first and second derivatives. The quality of PCA models was assessed using leave-one-out cross-validation and optimal number of principal components was determined. In the case of ATR spectra, the first principal component accounted for 42.92 % of the total variance among the samples and the optimal number of components was 6, whereas in the case of second derivatives the first principal component accounted for 95.76 % of the total variance and the optimal number of components was 3. Classification of olive oils on the basis of geographical origin was proposed and underlying spectral differences among the spectra were determined by investigating principal component loadings. These differences arise as a result of variations in fatty acid composition. It was found out that ATR in combination with PCA could easily distinguish between samples collected from the coastal area and those from the islands. Classification results were further confirmed by using spherical principal components procedure, projection pursuit and robust PCA, as well as hierarchical cluster analysis.(doi: 10.5562/cca2377