Concerted proton hopping in water

Protons hop from one water molecule to another given suitable energy conditions

2013-07-23

(Press-News.org) 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.

###

Publication:

Ali A. Hassanali et al.
Proton Transfer through the Water Gossamer
PNAS, 18 July 2013
DOI: 10.1073/pnas.1306642110

Image:

http://www.uni-mainz.de/bilder_presse/09_physchem_protonenleitung_01.jpg
Model of a hydrogen bridge bond network in liquid water
ill.: Thomas D. Kühne, JGU

Further information:

Professor Dr. Thomas D. Kühne
Institut of Physical Chemistry END

ELSE PRESS RELEASES FROM THIS DATE:

Perfecting digital imaging

2013-07-23

Cambridge, Mass. -- Computer graphics and digital video lag behind reality; despite advances, the best software and video cameras still cannot seem to get computer-generated images and digital film to look exactly the way our eyes expect them to. But Hanspeter Pfister and Todd Zickler, computer science faculty at the Harvard School of Engineering and Applied Sciences (SEAS), are working to narrow the gap between 'virtual' and 'real' by asking a common question: how do we see what we see? Between them, Pfister and Zickler are presenting three papers this week at SIGGRAPH ...

Optimists better at regulating stress

2013-07-23

This news release is available in French. Montreal, July 23, 2013 – It's no surprise that those who tend to see a rose's blooms before its thorns are also better at handling stress. But science has failed to reliably associate optimism with individuals' biological stress response – until now. New research from Concordia University's Department of Psychology is deepening the understanding of how optimists and pessimists each handle stress by comparing them not to each other but to themselves. Results show that indeed the "stress hormone" cortisol tends to be more ...

Purple bacteria on earth could survive alien light

2013-07-23

CORAL GABLES, FL (JULY 23, 2013) — Purple bacteria contain pigments that allow them to use sunlight as their source of energy, hence their color. Small as they are, these microbes can teach us a lot about life on Earth, because they have been around longer than most other organisms on the planet. University of Miami (UM) physicist Neil Johnson, who studies purple bacteria, recently found that these organisms can also survive in the presence of extreme alien light. The findings show that the way in which light is received by the bacteria can dictate the difference between ...

MU, K-State research team collaborate to save the bacon

2013-07-23

COLUMBIA, Mo. -- A research team from the University of Missouri and Kansas State University has been working to find a cure for a specific virus that affects pigs and costs the hog industry $800 million annually. In their latest study, the team disproved one way the virus spreads, which will help scientists narrow the search for an ultimate cure. Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) can inhibit pigs from reproducing and slow the growth of young pigs. Once pigs are infected, the only remedy is for hog farmers to cull their herds, which has cost ...

Scientists prove ticks harbor Heartland virus, a recently discovered disease in the United States

2013-07-23

DEERFIELD, IL. (JULY 22, 2013)— Scientists have for the first time traced a novel virus that infected two men from northwestern Missouri in 2009 to populations of ticks in the region, providing confirmation that lone star ticks are carrying the recently discovered virus and humans in the area are likely at risk of infection. The findings were published online today in the American Journal of Tropical Medicine and Hygiene. Dubbed Heartland virus or HRTV, the infection causes fever, headaches, and low white blood cell and platelet counts. The two men infected in 2009, who ...

Most flammable boreal forests in North America become more so

2013-07-23

CHAMPAIGN, Ill. — A 2,000-square-kilometer zone in the Yukon Flats of interior Alaska – one of the most flammable high-latitude regions of the world, according to scientists – has seen a dramatic increase in both the frequency and severity of fires in recent decades. Wildfire activity in this area is higher than at any other time in the past 10,000 years, the researchers report. The new findings add to the evidence that relatively frequent and powerful fires are converting the conifer-rich boreal forests of Alaska into deciduous woodlands. Deciduous trees, which shed ...

Bees 'betray' their flowers when pollinator species decline

2013-07-23

Remove even one bumblebee species from an ecosystem and the impact is swift and clear: Their floral "sweethearts" produce significantly fewer seeds, a new study finds. The study, to be published by the Proceedings of the National Academy of Sciences, focused on the interactions between bumblebees and larkspur wildflowers in Colorado's Rocky Mountains. The results show how reduced competition among pollinators disrupts floral fidelity, or specialization, among the remaining bees in the system, leading to less successful plant reproduction. "We found that these wildflowers ...

Plain packaging seems to make cigarettes less appealing and increase urgency to quit smoking

2013-07-23

Plain packaging for cigarettes seems to make tobacco less appealing and increase the urgency to quit smoking, suggest early findings from Australia, published in the online journal BMJ Open. Australia formally introduced plain brown packaging, accompanied by graphic health warnings taking up three quarters of the front of the pack, for all tobacco products on December 1 2012. So far, it is the only country in the world to have done so. The researchers wanted to find out what effects the policy was having in the early stages, and whether it helped curb the appeal of ...

Skipping breakfast may increase coronary heart disease risk

2013-07-23

Here's more evidence why breakfast may be the most important meal of the day: Men who reported that they regularly skipped breakfast had a higher risk of a heart attack or fatal coronary heart disease in a study reported in the American Heart Association journal Circulation. Researchers analyzed food frequency questionnaire data and tracked health outcomes for 16 years (1992-2008) on 26,902 male health professionals ages 45-82. They found: Men who reported they skipped breakfast had a 27 percent higher risk of heart attack or death from coronary heart disease than those ...

No benefit associated with echocardiographic screening in the general population

2013-07-23

A study in Norway suggests echocardiographic screening in the general public for structural and valvular heart disease was not associated with benefit for reducing the risk of death, myocardial infarction (heart attack) or stroke, according to a report published by JAMA Internal Medicine, a JAMA Network publication. Because of the low prevalence of structural heart disease in the general population, echocardiography has traditionally not been considered justified in low-risk individuals, although echocardiography is recommended for screening asymptomatic individuals with ...

NFCR congratulates Dr. Robert C. Bast, Jr. on receiving the AACR-Daniel D. Von Hoff Award for Outstanding Contributions to Education and Training in Cancer Research

Concerted proton hopping in water

ELSE PRESS RELEASES FROM THIS DATE:

LAST 30 PRESS RELEASES: