| Popis: |
Studies on the Mg(II) and Ca(II) complexes of four diastereomeric cyclohexane-1,2,4-triol trisphosphates were conducted using 1H NMR, 31P NMR, and calcium ion selective electrode (ISE) titrations. Based on the trends in Mg(II) and Ca(II) ion affinity, the 2,4-phosphate groups were concluded to be the primary determinants of the metal ion binding behavior of the 1,2,4-trisphosphates. Results from the proton and metal ion binding studies of the 1,2,4-trisphosphates indicate that the 1,2,4-trisphosphates satisfy two of the criteria as analogs of phospholipid-metal ion binding sites: (1) anionic groups which interact in metal ion binding, and (2) metal ion affinity constants determined by both ISE and 31P NMR titrations are comparable to the metal ion affinity observed for phosphatidylserine vesicles. In particular, the all-cis trisphosphate diastereomer, (±)-(1R, 2S, 4S)-cyclohexane-1,2,4-triol trisphosphate, is the only 1,2,4-trisphosphate to exhibit a higher affinity for Ca(II) ion than Mg(II) ion. A higher Ca(II) ion affinity than Mg(II) ion affinity is characteristic of the behavior observed for phosphatidylserine vesicles or monolayers. |
