Dissociation constants of water-insoluble carboxylic acids by 13C-NMR. pK(a)s of mesobiliverdin-XIII alpha and mesobilirubin-XIII alpha.
High-field 13C-NMR of 13C-enriched compounds in dilute aqueous d6-Me2-SO solutions provides a simple, accurate method for measuring pK(a)s of sparingly soluble carboxylic acids. Using this method, we found the pK(a)s of mesobilirubin-XIII alpha to be 4.2 and 4.9, much lower values than reported recently for bilirubin, and of mesobiliverdin-XIII alpha to be 3.9 and 5.3.
Lightner
D A
DA
Department of Chemistry, University of Nevada, Reno 89557-0020, USA.
Holmes
D L
DL
McDonagh
A F
AF
D001663:Bilirubin / Q000737:chemistry*; D001664:Biliverdine / Q000737:chemistry*; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D015394:Molecular Structure; D012995:Solubility; D012996:Solutions; D014867:Water
D012996:Solutions; D014867:Water; D001664:Biliverdine; D001663:Bilirubin