Low solubility of unconjugated bilirubin in Dimethylsulfoxide - Water Systems: Implications for pKa determinations

Aqueous pK a values of unconjugated bilirubin are important determinants of its solubility and transport. Published pK a data on an analog, mesobilirubin-XIIIα, studied by 13C-NMR in buffered solutions containing 27 and 64 vol% (C2H3)2SO because of low aqueous solubility of mesobilirubin, were extrapolated to obtain pK a values in water of 4.2 and 4.9. Previous chloroform-water partition data on bilirubin diacid led to higher estimates of its pK a , 8.12 and 8.44, and its aqueous solubility. A thermodynamic analysis, using this solubility and a published solubility in DMSO, suggested that the systems used to measure 13C-NMR shifts were highly supersaturated. This expectation was assessed by measuring the residual concentrations of bilirubin in the supernatants of comparable DMSO-buffer systems, after mild centrifugation to remove microprecipitates.



Titolo: Low solubility of unconjugated bilirubin in Dimethylsulfoxide - Water Systems: Implications for pKa determinations
Autori: 
TIRIBELLI, CLAUDIO
mostra contributor esterni 
Data di pubblicazione: 2002
Rivista: 
BMC BIOCHEMISTRY  
Abstract: Aqueous pK a values of unconjugated bilirubin are important determinants of its solubility and transport. Published pK a data on an analog, mesobilirubin-XIIIα, studied by 13C-NMR in buffered solutions containing 27 and 64 vol% (C2H3)2SO because of low aqueous solubility of mesobilirubin, were extrapolated to obtain pK a values in water of 4.2 and 4.9. Previous chloroform-water partition data on bilirubin diacid led to higher estimates of its pK a , 8.12 and 8.44, and its aqueous solubility. A thermodynamic analysis, using this solubility and a published solubility in DMSO, suggested that the systems used to measure 13C-NMR shifts were highly supersaturated. This expectation was assessed by measuring the residual concentrations of bilirubin in the supernatants of comparable DMSO-buffer systems, after mild centrifugation to remove microprecipitates.
Handle: http://hdl.handle.net/11368/2852998
Digital Object Identifier (DOI): http://dx.doi.org/10.1186/1471-2091-3-17
Appare nelle tipologie:1.1 Articolo in Rivista

File in questo prodotto:
Non ci sono file associati a questo prodotto.

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
 
 
 
©2014 University of Trieste dove siamo Privacy
Piazzale Europa,1 34127 Trieste, Italia - Tel. +39 040.558.7111 - P.IVA 00211830328 - C.F. 80013890324 - P.E.C.: ateneo@pec.units.it
 Copyright © 2021