Proton dissociation dynamics in the aqueous layer of multilamellar phospholipid vesicles
- 55 Downloads
The water layers interspacing between the phospholipid membranes of a multilamellar vesicle are 3–10 water layers across and their width is adjusted by osmotic pressure (Parsegian, V.A., et al., 1986.Methods Enzymol.127:400–416).
In these thin water layers we dissolved pyranine (8 hydroxypyrene 1,3,6 trisulfonate), a compound which, upon photo excitation, ejects it hydroxy proton with time constant of 100 psec. (Gutman, M. 1986.Methods Enzymol.127:522–538).
In the present study we investigated how the width of the aqueous layer, the density of phosphomoieties on the membrane's surface and the activity of water in the layer affect the capacity of protons to diffuse out from the electrostatic cage of the excited anion before it decays to the ground state.
Using a combination of steady-state and subnanosecond time-resolved fluorescence measurements we determined the average number of proton excited-anion recombinations before the proton escapes from the Coulomb cage.
The probability of recombination in thin water layer is significantly higher than in bulk. The factor contributing most to enhancement of recombination is the diminished water activity of the thin aqueous layer.
The time frame for proton escape from an electrostatic trap as big as a membrane-bound protein is 3 orders of magnitude shorter than turnover time of membrane-bound enzymes. Thus the effects of local forces on proton diffusion, at the time scale of physiological processes, is negligible.
Key Wordshydration layer water activity multilamellar vesicles pH jump proton diffusion dissociation dynamics
Unable to display preview. Download preview PDF.
- Agmon, N. 1988. Geminate recombination in proton-transfer reaction. III. Kinetics and equilibrium inside a finite sphere.J. Chem. Phys. 88:5639–5642Google Scholar
- Agmon, N., Pines, E., Huppert, D. 1988. Geminate recombination in proton-transfer reaction. II. Comparison with diffusional and kinetic schemes.J. Chem. Phys. 88:5631–5638Google Scholar
- Bardez, E., Goguillon, B.T., Keh, E., Valeur, B. 1984. Dynamics of excited-state reactions in reversed micelles. I. Proton transfer involving a hydrophilic fluorescent probe.J. Phys. Chem. 88:1909–1913Google Scholar
- Brzezinski, B., Zundel, G., Kramer, R. 1987. Proton polarizability caused by collective proton motion in intramolecular chains formed by two and three H bonds. Implications for charge conduction in bacterial rhodopsin.J. Phys. Chem. 91:3077–3080Google Scholar
- Gutman, M., Nachliel, E. 1990. The dynamic aspects of proton transfer processes.Biochim. Biophys. Acta 1015:391–414Google Scholar
- Hubbard, J., Onsager, L. 1977. Dielectric dispersion and dielectric friction of electrolytic solution.J. Chem. Phys. 67:4850–4857Google Scholar
- Huppert, D., Kolodney, E., Gutman, M., Nachliel, E. 1982. Effect of water activity on the rate of proton dissociation.J. Am. Chem. Soc. 104:6949–6953Google Scholar
- Kjellander, R., Marcelja, S. 1988. Inhomogeneous Coulomb fluids with image interaction between planar surfaces. III. Distribution functions.J. Chem. Phys. 88:7138–7146Google Scholar
- McIntosh, T.J., Magid, A.D., Simon, S.A. 1987. Steric repulsion between phosphatidylcholine membranes.Biochemistry 26:7323–7325Google Scholar
- Nachliel, E., Gutman, M. 1988. Time resolved proton-phospholipid interaction methodology and kinetic analysis.J. Am. Chem. Soc. 110:2629–2635Google Scholar
- Pines, E., Huppert, D. 1989. Salt effect in photo-acids quantum yields measurements: A demonstration of the geminate recombination role in deprotonation reactions.J. Am. Chem. Soc. 111:4096–4097Google Scholar
- Pines, E., Huppert, D., Agmon, N. 1988. Geminate recombination in excited state proton transfer reactions: I. Numerical solution of the Debye-Smoluchowski equation with back reaction and comparison with experimental results.J. Chem. Phys. 88:5620–5630Google Scholar
- Politi, M.J., Chaimovich, H. 1986. Water activity in reversed sodiumBis (2-ethylhexyl)sulfosuccinate micelles.J. Phys. Chem. 90:282–287Google Scholar
- Rand, R.P., Parsegian, V.A. 1989. Hydration layer between phospholipid bilayers.Biochim. Biophys. Acta 988:351–376Google Scholar
- Rand, R.P., Parsegian, V.A., Henry, J.A.C., Lis, L.J., McAlister, M. 1980. The effect of cholesterol on measured interactions and compressibility of dipalmitoyl phosphotidyl vesicles.Can. J. Biochem. 59:959–968Google Scholar
- Robinson, R.A., Stokes, R.H. 1954. Electrolyte Solutions Appendix 8. G. Butterworth Scientific, LondonGoogle Scholar
- Zundel, G., Roberts, N.K. 1980. Long range structuring of water by quartz and glass surface as indicated by infrared continuum and diffusion coefficient of excess protons.J. Phys. Chem. 84:3655–3660Google Scholar