title: Protonation effect on drug affinity.
abstract: Pharmacologic ligand-macromolecule interactions are commonly characterized by affinity (dissociation) constants such as K(d) or K(i) without regard to the protonation effect of the buffer used in the measurement. The protonation effect is demonstrated here using isothermal titration microcalorimetry measurements of the competitive inhibitor binding of cytidine 2'-monophosphate (2'-CMP) to RNase-A as a model system in buffers of different ionization Delta H(buffer). The results demonstrate the importance of protonation in measures of affinity.
authors.affiliation: Department of Pharmaceutical Sciences, School of Pharmacy, Temple University, Philadelphia, PA 19140, USA. robert.raffa@temple.edu
authors.forename: Robert B
authors.initials: RB
authors.lastname: Raffa
authors.forename: Gregory W
authors.initials: GW
authors.lastname: Stagliano
authors.forename: Shawn D
authors.initials: SD
authors.lastname: Spencer
mesh_terms: D002021:Buffers; D002151:Calorimetry / Q000379:methods; D002152:Calorimetry, Differential Scanning / Q000379:methods; D007700:Kinetics; D008024:Ligands; D004364:Pharmaceutical Preparations / Q000737:chemistry* / Q000378:metabolism*; D011522:Protons; D013816:Thermodynamics
chemical_list: D002021:Buffers; D008024:Ligands; D004364:Pharmaceutical Preparations; D011522:Protons