TY - JOUR
T1 - Phosphate assisted proton transfer in water and sugar glasses
T2 - A study using fluorescence of pyrene-1-carboxylate and IR spectroscopy
AU - Zelent, Bogumil
AU - Vanderkooi, Jane M.
AU - Nucci, Nathaniel V.
AU - Gryczynski, Ignacy
AU - Gryczynski, Zygmunt
N1 - Funding Information:
Acknowledgment This work was supported by NIH grant PO1 GM48130 (J.M.V.), Texas Emerging Technologies Fund (Z.G. and I. G.) and fellowship NIH F31 NSO53399 to NVN. We thank Jennifer Dashnau, Jennifer Greene and Nathan Scott for helpful discussions.
PY - 2009/1
Y1 - 2009/1
N2 - 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.
AB - 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.
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U2 - 10.1007/s10895-008-0375-5
DO - 10.1007/s10895-008-0375-5
M3 - Article
C2 - 18496739
AN - SCOPUS:59849124860
SN - 1053-0509
VL - 19
SP - 21
EP - 31
JO - Journal of Fluorescence
JF - Journal of Fluorescence
IS - 1
ER -