Abstract

Proton Mobility in Cell-like Environments

Ines Hauner, Researcher, University of Amsterdam

Recent experiments reveal the presence of strong spatial heterogeneities of the intracellular proton concentration even in the absence of physical diffusion barriers such as biological membranes. This is, however, at odds with the well established ultrafast Grotthus mechanism for proton diffusion. We present first measurements of proton mobility in cell-like environments using Microfluidic Fluorescence Microscopy and Time-Resolved Femtosecond IR Spectroscopy. We find that the proton mobility can be several orders of magnitude slower because cytosolic components retard diffusion at physiological, i.e. cell mimicking conditions. On the other hand, the water reorientation dynamics that plays a preponderant role for the Grotthus mechanism is hardly changed. This allows us to conclude that the deceleration of proton diffusion is primarily due to the proton carrying capacity of weak acids and bases as well as to effects resulting from the presence of biological macromolecules such as globular proteins.