Role of Proton Gradients in the Mechanism of Osmosis

Abstract

Experiments were carried out to determine whether the newly identified "exclusion zone" found adjacent to hydrophilic surfaces might play a role in osmosis. Two chambers were juxtaposed face to face, separated by a membrane made of cellulose acetate or Nafion. One chamber contained water, the other 100 mM sodium sulfate solution. Osmotically driven transmembrane fluid flow from low to high salt was observed using both membranes, in agreement with previous reports. Characteristic pH differences and potential differences between chambers were also noted. Visual examination with microsphere markers revealed extensive exclusion zones adjacent to both types of membrane. As these zones routinely generate protons in the water regions beyond, unequal proton concentrations in the respective chambers may be responsible for creating both the pH and potential gradients, which may be ultimately responsible for the osmotic drive.

Exclusion-zone formation from discontinuous nafion surfaces

“…The uncoated side showed no EZ formation. The sprayed-on Nafion EZs were similar in size to EZs using Nafion-117 sheets [5, 7, 15]. …”

“…More recent evidence [5, 6] reveals that these exclusion zones represent a state of water that is more ordered than bulk water. The ordering is hypothesized to produce the observed exclusion, as well as the electric potential and pH gradients.…”

“…The ordering is hypothesized to produce the observed exclusion, as well as the electric potential and pH gradients. Such features of the exclusion zones (EZs) offer promising applications such as water purification [7], mechanical sorting [5, 8–10], power storage [4] and potentially new water-based chemistries that take advantage of the properties of interfacial water in enzyme-assisted reactions [11]. …”

V‐ATPase‐dependent ectodermal voltage and ph regionalization are required for craniofacial morphogenesis

“…4A.ii), suggesting that H + ‐V‐ATPase inhibition affects cell shape. Differences in pH influence osmotic pressure in cells (Zhao et al,2009), and are likely to produce conditions where cell shape is affected either in the treated cells or in neighboring cells due to changes in permissive states. Further connections between pH and V mem via alterations in H + ‐flux and their effects on cell shape and size should be explored further.…”

“…V mem is known to regulate membrane proteins, for example voltage‐gated sodium, potassium, and chloride channels; pH affects protein conformation and enzyme activity. It has recently been shown that pH may also regulate osmosis and thus osmotic pressure in cells (Zhao et al,2009); therefore, regulated pH differences could provide motive force or establish permissive conditions for cell shape changes (Ingber,2006).…”