Origin of the energy barrier that opposes proton surface-to-bulk release
Sprache des Vortragstitels:
European Biophysical Societies'
Sprache des Tagungstitel:
The concept of surface coupled proton exchange between
membrane proteins has long been criticized because the origin
of proton?s surface affinity remained enigmatic. The weak
dependence of both migration speed and span on lipid composition
suggests that interfacial water serves as proton railways
(1). However, it is unclear how to reconcile the apparent
high proton affinity to the phase boundary (2) with
the poor proton acceptability of water. Here we monitored
the diffusion of excess protons along the phosphatidylcholine
lipid bilayer/water interface at different temperatures. The
kinetics of proton arrival from a distant spot of proton release
to lipid anchored fluorescent pH-sensitive dyes indicated that
the in vitro Gibbs activation energy ?G for proton surfaceto-
bulk release harbours only a minor enthalpic constituent.
Our observation that more than 2/3 of ?G are entropic in
origin explains the high proton affinity to membranes in the
absence of a potent proton acceptor.
This work was supported by Grant P25981 from the
Austrian Science Fund (FWF) to P.P.
1. Springer et al. (2011) 108, 14466.
2. Zhang et al. (2012) 109, 9744. E. Weichselbaum, D. Knyazev, P. Pohl