Determination of dissociation constants of cephalosporin antibiotics by cellmetry method

Acid dissociation constants of three cephalosporin antibiotics (cefapirin, ceftiofur, and cefotaxime) were calculated by a newly developed methodology. Plane-wave DFT calculations were performed to determine the pK_a values, and by choosing the appropriate cell sizes, accurate values could be calculated. Some characteristic points were found which helped us to find correlations among the structural and physic-chemical parameters, and correlation factors were defined as well. This present study can be a base for further approaches to determining acid dissociation constants of cephalosporin molecules.