Abstract
Raman spectra of ATP at various pH values are affected by addition of equimolar solution of divalent metal ions such as Ca2+, Mg2+, Co2+, Cu2+, and Hg2+. The changes in frequency and intensity have been used to construct models describing the nature of metal-adenine and metal-triphosphate interactions under different conditions. The metal ions are found to co-ordinate the triphosphate group in the entire pH range studies (pH to 12). Calcium (II) and magnesium (II) interact strongly with the phosphate moiety at neutral pH, although a weak interaction with the ring occur at low pH values. Around neutrality, several Raman spectral changes are observed to implicate the interaction of cobalt (II) ion with the five-membered ring of the adenine. The changes in Raman frequency are too small to suggest a direct Co(II)-N7 binding. At least six different Cu(II)-ATP species are identified between pH 3 and 12. At pH approximately 7.0 Raman data are explained better by Cu(II) interacting with N7 simultaneously with the amino group of the adenine ring. However, a Cu(II) binding to N3 at pH 10 to 11 is indicated by the enhancement of the 760 and 1360 cm-1 vibrations. At neutral pH, mercury (II) ion shows a direct coordination at N1 while at low pH with N1 blocked by protonation, mercury (II) does not interact with the adenine moiety.
Highlights
From the School of Chemistry, Georgia Institute of Technology, Atlanta, Raman spectra of ATP at various pH values are affected by addition of equimolar solution of divalent metal ions such as Ca’+, M8’, Co’+, Cu’+, and Hg’+
Calcium (II) and magnesium (II) interact strongly with the phosphate moiety at neutral pH, a weak interaction with the ring occur at low pH values
Several Raman spectral changes are observed to implicate the interaction of cobalt (II) ion with the five-membered ring of the adenine
Summary
From the School of Chemistry, Georgia Institute of Technology, Atlanta, Raman spectra of ATP at various pH values are affected by addition of equimolar solution of divalent metal ions such as Ca’+, M8’, Co’+, Cu’+, and Hg’+. The changes in frequency and intensity have been used to construct models describing the nature of metal-adenine and metal-triphosphate interactions under different conditions. Several Raman spectral changes are observed to implicate the interaction of cobalt (II) ion with the five-membered ring of the adenine. The changes in Raman frequency are too small to suggest a direct Co(II)-N7 binding. Most enzymatic reactions utilizing adenine nucleotides require divalent cations as cofactors. In many cases it was shown (l-3) that the real substrates for kinases and ATPases are the metal. The present knowledge pertaining to the nature of interactions comes mainly from magnetic resonance studies
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