PROTON · Proton transport and proton-coupled transport

Proton transport and proton-coupled transport

Secure, competitive, and sustainable energy production is a major challenge facing human societies. Biomimetic solutions such as the development of new biofuel cells are hampered by our thus far incomplete understanding of proton transfer reactions. The same holds for health threats to humanity: Curing diseases like cancer, obesity, chronic gastritis, gastric and duodenal ulcers, requires molecular details of yet unresolved proton transfer reactions. We aim to clarify the molecular reaction mechanism in the confines of interfacial water layers and proteinaceous cavities with emphasis on the arrangement and mobility of proton relay moieties. Achieving this requires an interdisciplinary, multi-level approach comprising cutting-edge technologies like second harmonic imaging, single-molecule and time-resolved fluorescence microscopy and spectroscopy, advanced calculations of proton transfer, bioengineering of membrane channel and transporter-containing systems, synthetic design of biomimetic proton channels, solving protein structures and rational drug design. Proton transfer is crucial in numerous biological and chemical processes, e.g. in cellular proton pumps or in hydrogen fuel cells. Even though their empirical study began with the origin of chemistry, many details of the proton transfer mechanism are still unresolved and understanding the way in which confined water mediates proton dynamics remains a fundamental challenge in chemistry and biochemistry. Transmembrane proton gradients are essential to life on earth as they are intricately linked to both photosynthesis and synthesis of adenosine triphosphate (ATP, the energy currency of life). Yet, once protons have crossed the membrane, they do not freely exchange with protons on the receiving site. An energy barrier with the height of ~30 kT opposes their release into the bulk. The mainly entropic nature of the barrier ensures high lateral proton mobility. However, besides being attributed to structured water, the molecular origin of that barrier remained thus far elusive. Yet, newly developed label-free and charge-sensitive dynamic imaging techniques of lipid membrane hydration, hydration of active protein sites as well as their dipolar relaxation dynamics now offer the possibility to explore the interplay between structural features of the hydration shell and proton migration on the millisecond time scale. Likewise, technically demanding ab-initio molecular dynamics (MD) simulations of protons adjacent to lipid bilayers also promise insight into the molecular proton migration mechanism. By levering on these new methods for (i) visualising proton surface transport as well as (ii) assessing its energetics and combining them with approaches for deciphering the structure of G-protein-coupled receptors (GPCRs) and other proton-dependent membrane protein, the PROTON project will perform ground-breaking work in this field.

Data: CORDIS, © European Union