Protons, as positively charged hydrogen ions, move very rapidly in water from one water molecule to the next, which is why the conductivity of water is relatively high.
The principle of proton conduction in water has been known for 200 years and is named the Grotthuss mechanism after its discoverer, Theodor Grotthuss. It is based on the assumption that it is not that a single specific proton moving from one molecule to another; instead, there is cleavage of bonds. One proton docks onto a molecule and this causes another proton to leave that molecule and bind to another molecule somewhere else.
This proton exchange mechanism has been compared to a 'bucket line' to explain the rapid diffusion of the individual protons. However, this concept oversimplifies the situation and belies the complexity of the structure of water. Researchers from Zurich and Mainz have now been able to analyze the mechanism in more detail using theoretical calculations and have shown that the currently accepted picture of proton diffusion may need to be revised.
"The simulation shows that the crossover from one water molecule to the next occurs more quickly than previously thought and then there is a rest period until the next crossover," said Professor Thomas D. Kühne of the Institute of Physical Chemistry at Johannes Gutenberg University Mainz (JGU), describing the results. These were published online on July 18, 2013 in the journal Proceedings of the National Academy of Sciences.
"We show that the diffusion of protons and hydroxide ions occurs during periods of intense activity involving concerted proton hopping, followed by periods of rest," wrote primary author Ali A. Hassanali of the Swiss Federal Institute of Technology Zurich in the publication. In the model of proton diffusion that researchers have now developed, the hydrogen bridge network is equivalent to an aggregation of closed rings. The resulting proton chains serve as a 'road' in the hydrogen bridge network that make possible long proton jumps across multiple hydrogen bridge bond formations. "The water molecules 'dance' around each other until they achieve an energetically favorable status. Only then will a proton hop along the 'road' to another molecule," explained Kühne. As a result, there is temporary formation of protonated water molecules with three protons.
In addition to the relevance of proton transfer in aqueous systems, the results may also be applicable to important biological systems such as enzymes and macromolecules.
Petra Giegerich | idw
Colorectal cancer: Increased life expectancy thanks to individualised therapies
20.02.2020 | Christian-Albrechts-Universität zu Kiel
Sweet beaks: What Galapagos finches and marine bacteria have in common
20.02.2020 | Max-Planck-Institut für Marine Mikrobiologie
The operational speed of semiconductors in various electronic and optoelectronic devices is limited to several gigahertz (a billion oscillations per second). This constrains the upper limit of the operational speed of computing. Now researchers from the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg, Germany, and the Indian Institute of Technology in Bombay have explained how these processes can be sped up through the use of light waves and defected solid materials.
Light waves perform several hundred trillion oscillations per second. Hence, it is natural to envision employing light oscillations to drive the electronic...
Most natural and artificial surfaces are rough: metals and even glasses that appear smooth to the naked eye can look like jagged mountain ranges under the microscope. There is currently no uniform theory about the origin of this roughness despite it being observed on all scales, from the atomic to the tectonic. Scientists suspect that the rough surface is formed by irreversible plastic deformation that occurs in many processes of mechanical machining of components such as milling.
Prof. Dr. Lars Pastewka from the Simulation group at the Department of Microsystems Engineering at the University of Freiburg and his team have simulated such...
Investigation of the temperature dependence of the skyrmion Hall effect reveals further insights into possible new data storage devices
The joint research project of Johannes Gutenberg University Mainz (JGU) and the Massachusetts Institute of Technology (MIT) that had previously demonstrated...
Researchers at Chalmers University of Technology, Sweden, recently completed a 5-year research project looking at how to make fibre optic communications systems more energy efficient. Among their proposals are smart, error-correcting data chip circuits, which they refined to be 10 times less energy consumptive. The project has yielded several scientific articles, in publications including Nature Communications.
Streaming films and music, scrolling through social media, and using cloud-based storage services are everyday activities now.
After helping develop a new approach for organic synthesis -- carbon-hydrogen functionalization -- scientists at Emory University are now showing how this approach may apply to drug discovery. Nature Catalysis published their most recent work -- a streamlined process for making a three-dimensional scaffold of keen interest to the pharmaceutical industry.
"Our tools open up whole new chemical space for potential drug targets," says Huw Davies, Emory professor of organic chemistry and senior author of the paper.
12.02.2020 | Event News
16.01.2020 | Event News
15.01.2020 | Event News
21.02.2020 | Medical Engineering
21.02.2020 | Health and Medicine
21.02.2020 | Physics and Astronomy