P-31 NMR-STUDIES OF ISOPRENOID POLYPHOSPHATE ACID-BASE EQUILIBRIA

Isoprenoid polyphosphate intermediates of the mevalonate pathway were studied using P-31 NMR, Acid-base titrations of farnesyl and geranylge ranyl polyphosphates were conducted over the pH range 4-10, and P-31 c hemical shifts were used to determine pK(a)' values for the second ion ization step of the terminal phosphate groups, Apparent pK(a) values r anged from 6.16 to 7.07, which may have important implications for bio logical reactions involving these and similar molecules, In general, a cid-catalyzed hydrolysis of the phosphomonoesters had Little effect on the determination of pK(a)' values during the course of this study. ( C) 1997 by John Wiley & Sons, Ltd.