DFT pr ediction on pKa of L-dopa in an aqueo us solution

Levedopa (۳,۴-dihy droxyphenylalanine, L- dopa) [۱] is a very im portant compound that is consider ed for Parkinson’s disease in parts of brain. P redicting pr operties of L-dopa is an interestin g subject of research . Several methods ha ve been developed for predictin g properties of compo unds such as QSPR [۲], QSAR [۳], and ab intio/DFT methods [۴ ]. Quantum mechanical methods have been pr eviously used to investi gate and to p redict acidity constants of differen t acids or bases [۵]. I n this paper, by means of DFT method, acidity constant of L-dopa is predicted.Geometry of each compound w as fully op timized at B ۳LYP/۶-۳۱++G(d,p), and B۳LYP/۶-۳۱۱++G( d,p) levels of theory [۶]. Total free energy of each compound in water was calculated using CPCM and S MD models at the HF/۶-۳۱G and HF/۶-۳۱G( d,p) levels of theory to evaluate pKa values. All of the t heoretical c lculations were carried out with t he Gaussian ۲۰۰۹ suite of program s, and molecules were drawn by GaussView ۵.۰ progra m. Comparing the results,one can find out t hat increasing the basis set of th eory yields a significant improvem ent in the calculated pK a values . Data show sig nificant effects hydroge n bonding in CPCM model

کلیدواژه ها:

L-dopa ، acidity constant ، DFT ، hydrogen bo nding