| Autor: |
Sokolov VS; Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Leninsky Prospekt, 31, Moscow 119071, Russia., Tashkin VY; Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Leninsky Prospekt, 31, Moscow 119071, Russia., Zykova DD; Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Leninsky Prospekt, 31, Moscow 119071, Russia.; Moscow Institute of Physics and Technology, Institutski Per., 9, Moscow Region, Dolgoprudny 141701, Russia., Kharitonova YV; Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Leninsky Prospekt, 31, Moscow 119071, Russia., Galimzyanov TR; Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Leninsky Prospekt, 31, Moscow 119071, Russia., Batishchev OV; Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Leninsky Prospekt, 31, Moscow 119071, Russia. |
| Abstrakt: |
Lateral transport and release of protons at the water-membrane interface play crucial roles in cell bioenergetics. Therefore, versatile techniques need to be developed for investigating as well as clarifying the main features of these processes at the molecular level. Here, we experimentally measured the kinetics of binding of protons released from the photoactivated compound sodium 2-methoxy-5-nitrophenyl sulfate (MNPS) at the surface of a bilayer lipid membrane (BLM). We developed a theoretical model of this process describing the damage of MNPS coupled with the release of the protons at the membrane surface, as well as the exchange of MNPS molecules and protons between the membrane and solution. We found that the total change in the boundary potential difference across the membrane, ∆ϕ b , is the sum of opposing effects of adsorption of MNPS anions and release of protons at the membrane-water interface. Steady-state change in the ∆ϕ b due to protons decreased with the concentration of the buffer and increased with the pH of the solution. The change in the concentration of protons evaluated from measurements of ∆ϕ b was close to that in the unstirred water layer near the BLM. This result, as well as rate constants of the proton exchange between the membrane and the bulk solution, indicated that the rate-limiting step of the proton surface to bulk release is the change in the concentration of protons in the unstirred layer. This means that the protons released from MNPS remain in equilibrium between the BLM surface and an adjacent water layer. |
