关键词: Fukui function, L-Ornithine, Softness and hardness, Reactivity descriptor, pKa, Ab initio and DFT

Abstract:

L-ornithine is a metabolic product of L-arginine and is found in the liver and other tissues after the enzyme arginase in the urea cycle catalyses the reaction. The presence of L-ornithine has an influence on certain biochemical activities such as the proliferation of collagen production and also has an effect on airway responsiveness. Therefore, it has a role to play in the availability of nitric oxide (NO). A brief reactivity study was carried out for various substituents at the α-C atomof this amino acid. Substituents such as chlorine and fluorine affect the reactivity of the entire molecule and may alter the properties of the amino acid. To understand the properties of molecule, a detailed study was done at the density functional theory (DFT) level and compared with ab initio calculations. Fukui functions were invoked to assess reactivity and stability. The descriptive properties were correlated to logP or pKa using available software to help build a model to quantitatively assess properties and reactivity. Results showed a randomreactivity pattern upon halogen substitution and this indicates the need to exercise caution during docking and reactivity studies.

Key words: Fukui function, L-Ornithine, Softness and hardness, Reactivity descriptor, pKa, Ab initio and DFT