31P NMR STUDIES OF ISOPRENOID POLYPHOSPHATE ACID-BASE EQUILIBRIA

Isoprenoid polyphosphate intermediates of the mevalonate pathway were studied using 31P NMR. Acid–base titrations of farnesyl and geranylgeranyl polyphosphates were conducted over the pH range 4–10, and 31P chemical shifts were used to determine pKa′ values for the second ionization step of the terminal phosphate groups. Apparent pKa values ranged from 6.16 to 7.07, which may have important implications for biological reactions involving these and similar molecules. In general, acid-catalyzed hydrolysis of the phosphomonoesters had little effect on the determination of pKa′ values during the course of this study. © 1997 John Wiley & Sons, Ltd.