Quantum-Chemieal Modeling of Cateeholamine Storage Including Continuum Solvent Effeets

Abstract

A model for catecholamine storage in vesicles is analyzed within the ,CRI CNDO/2 approach inc1uding conlinuum solvenl crfcels. The model considers lhe approach of calionic norepinephrine (NE) 10 a positively charged guanidinium moiely. lon-pair formalion is found for ¡he whole range of dielectrie eonslanls. [ven though slablc slales of II-bonded parlnns are found for Jarge diclcctric constants, this proecss is ruled out to occur bccause it involvcs 100 high cnergies. 11 appears that the medium's polarily is determinant in lowering the energy barrier between the ion-pair complex and the separatcd parlners. Thus, as the mediul11 dielectric constanl increases. ¡he equilibrium between the two statcs is enhanced. Introduction