Phosphate assisted proton transfer in water and sugar glasses: A study using fluorescence of pyrene-1-carboxylate and IR spectroscopy

Bogumil Zelent, Jane M. Vanderkooi, Nathaniel V. Nucci, Ignacy Gryczynski, Zygmunt Gryczynski

Research output: Contribution to journalArticle

5 Scopus citations

Abstract

The role of water's H-bond percolation network in acid-assisted proton transfer was studied in water and glycerol solutions and in sugar glasses. Proton transfer rates were determined by the fluorescence of pyrene-1-carboxylate, a compound with a higher pK in its excited state relative to the ground state. Excitation of pyrene-1-COO - produces fluorescence from pyrene-1-COOH when a proton is accepted during the excited singlet state lifetime of pyrene-1-COO -. The presence of glycerol as an aqueous cosolvent decreases proton transfer rates from phosphoric and acetic acid in a manner that does not follow the Stokes relationship on viscosity. In sugar glass composed of trehalose and sucrose, proton transfer occurs when phosphate is incorporated in the glass. Sugar glass containing phosphate retains water and it is suggested that proton transfer requires this water. The infrared (IR) frequency of water bending mode in sugar glass and in aqueous solution is affected by the presence of phosphate and the IR spectral bands of all phosphate species in water are temperature dependent; both results are consistent with H-bonding between water and phosphate. The fluorescence results, which studied the effect of cosolvent, highlight the role of water in assisting proton transfer in reactions involving biological acids, and the IR results, which give spectroscopic evidence for H-bonding between water and phosphate, are consistent with a mechanism of proton transfer involving H-bonding. The possibility that the phosphate-rich surface of membranes assists in proton equilibration in cells is discussed.

Original languageEnglish
Pages (from-to)21-31
Number of pages11
JournalJournal of Fluorescence
Volume19
Issue number1
DOIs
StatePublished - 1 Jan 2009

Keywords

  • Glycerol
  • Membranes
  • Percolation
  • Phospholipids
  • Proton transfer
  • Water

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