Nanotechnology Now







Heifer International

Wikipedia Affiliate Button


DHgate

Home > Press > In water as in love, likes can attract

This model of the guanidinium chloride salt (blue and silver) in solution shows carbon (yellow) and water (green) surrounding the cations and demonstrates cation-cation pairing.
This model of the guanidinium chloride salt (blue and silver) in solution shows carbon (yellow) and water (green) surrounding the cations and demonstrates cation-cation pairing.

Abstract:
At some point in elementary school you were shown that opposite charges attract and like charges repel. This is a universal scientific truth - except when it isn't. A research team led by Berkeley Lab chemist Richard Saykally and theorist David Prendergast, working at the Advanced Light Source (ALS), has shown that, when hydrated in water, positively charged ions (cations) can actually pair up with one another.

In water as in love, likes can attract

Berkeley, CA | Posted on September 19th, 2013

"Through a combination of X-ray spectroscopy, liquid microjets and first principles' theory, we've observed and characterized contact pairing between guanidinium cations in aqueous solution," Saykally says. "Theorists have predicted this cation-to-cation pairing but it has never been definitively observed before. If guanidinium cations can pair this way, then other similar cation systems probably can too."

Guanidinium is an ionic compound of hydrogen, nitrogen and carbon atoms whose salt - guanidinium chloride - is widely used by scientists to denature proteins for protein-folding studies. This practice dates back to the late 19th century when the Czech scientist Franz Hofmeister observed that cations such as guanidinium can pair with anions (negatively charged ions) in proteins to cause them to precipitate. The Hofmeister effect, which ranks ions on their ability to "salt-out" proteins, became a staple of protein research even though its mechanism has never been fully understood.

In 2006, Kim Collins of the University of Maryland proposed a "Law of Matching Water Affinities" to help explain "Hofmeister effects". Collins's proposal holds that the tendency of a cation and anion to form a contact pair is governed by how closely their hydration energies match, meaning how strongly the ions hold onto molecules of water. Saykally, who is a faculty scientist in Berkeley Lab's Chemical Sciences Division and a professor of chemistry at the University of California Berkeley, devised a means of studying both the Law of Matching Water Affinities and Hofmeister effects. In 2000, he and his group incorporated liquid microjet technology into the high-vacuum experimental environment of ALS beamlines and used the combination to perform the first X-ray absorption spectroscopy measurements on liquid samples. This technique has since become a widely used research practice.

"The XAS spectrum is generally sensitive to the changes in the local solvation environment around each atom, including potential effects of ion-pairing," Saykally says. "However, the chemical information that one can extract from such experimental data alone is limited, so we interpret our spectra with a combination of molecular dynamics simulations and a first principles theory method."

Development of this first principles theory method was led by Prendergast, a staff scientist in the Theory of Nanostructures Facility at Berkeley Lab's Molecular Foundry. Computational resources were provided by the National Energy Research Scientific Computing Center (NERSC). The Molecular Foundry and NERSC, as well as the ALS, are all U.S. Department of Energy national user facilities hosted at Berkeley Lab.

With the liquid microjet technology, a sample rapidly flows through a fused silica capillary shaped to a finely tipped nozzle with an opening only a few micrometers in diameter. The resulting liquid beam travels a few centimeters in a vacuum chamber and is intersected by an X-ray beam then collected and condensed out. In analyzing their current results, which were obtained at ALS Beamline 8.0.1, the Berkeley Lab researchers concluded that the counterintuitive cation-cation pairing observed is driven by water-binding energy, as predicted by theory.

Orion Shih, a recent graduate of Saykally's research group, is the lead author of a paper describing this study in the Journal of Chemical Physics. The paper is titled "Cation-cation contact pairing in water: Guanidinium." Saykally is the corresponding author. Other co-authors are Alice England, Gregory Dallinger, Jacob Smith, Kaitlin Duffey, Ronald Cohen and Prendergast.

"We found that the guanidinium ions form strong donor hydrogen bonds in the plane of the molecule, but weak acceptor hydrogen bonds with the pi electrons orthogonal to the plane," Shih says. "When fluctuations bring the solvated ions near each other, the van der Waals attraction between the pi electron clouds squeezes out the weakly held water molecules, which move into the bulk solution and form much stronger hydrogen bonds with other water molecules. This release of the weakly interacting water molecules results in contact pairing between the guanidinium cations. We believe our observations may set a general precedent in which like charges attract becomes a new paradigm for aqueous solutions."

####

For more information, please click here

Contacts:
Lynn Yarris

510-486-5375

Copyright © DOE/Lawrence Berkeley National Laboratory

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related Links

For more about Richard Saykally and his research group go here:

For more about Berkeley Labís Advanced Light Source go here:

For more about Berkeley Labís Molecular Foundry go here:

For more about NERSC go here:

Related News Press

News and information

Toyocolor to Launch New Carbon Nanotube Materials at nano tech 2015 January 24th, 2015

NANOPOSTER 2015 - 5th Virtual Nanotechnology Conference - call for abstracts January 24th, 2015

Nanosensor Used for Simultaneous Determination of Effective Tea Components January 24th, 2015

The latest fashion: Graphene edges can be tailor-made: Rice University theory shows it should be possible to tune material's properties January 24th, 2015

Chemistry

Anti-microbial coatings with a long-term effect for surfaces Ė presentation at nano tech 2015 in Japan January 21st, 2015

Hydrogels deliver on blood-vessel growth: Rice researchers introduce improved injectable scaffold to promote healing January 20th, 2015

Graphene enables all-electrical control of energy flow from light emitters: First signatures of graphene plasmons at telecommunications wavelength revealed January 20th, 2015

Physics

Nano-beaker offers insight into the condensation of atoms January 21st, 2015

Atoms can be in 2 places at the same time: Researchers of the University of Bonn have shown that cesium atoms do not follow well-defined paths January 20th, 2015

Laboratories

Self-assembled nanotextures create antireflective surface on silicon solar cells: Nanostructured surface textures-with shapes inspired by the structure of moths' eyes-prevent the reflection of light off silicon, improving conversion of sunlight to electricity January 21st, 2015

Govt.-Legislation/Regulation/Funding/Policy

The latest fashion: Graphene edges can be tailor-made: Rice University theory shows it should be possible to tune material's properties January 24th, 2015

Scientists 'bend' elastic waves with new metamaterials that could have commercial applications: Materials could benefit imaging and military enhancements such as elastic cloaking January 23rd, 2015

Harper Government Supports Research Innovation in Western Canada January 22nd, 2015

EnvisioNano: An image contest hosted by the National Nanotechnology Initiative (NNI) January 22nd, 2015

Discoveries

Nanosensor Used for Simultaneous Determination of Effective Tea Components January 24th, 2015

The latest fashion: Graphene edges can be tailor-made: Rice University theory shows it should be possible to tune material's properties January 24th, 2015

Iranian Scientists Produce Graphene-Based Oxygen Sensor January 23rd, 2015

Silver nanowires demonstrate unexpected self-healing mechanism: The material has potential for flexible electronics January 23rd, 2015

Announcements

Toyocolor to Launch New Carbon Nanotube Materials at nano tech 2015 January 24th, 2015

NANOPOSTER 2015 - 5th Virtual Nanotechnology Conference - call for abstracts January 24th, 2015

Nanosensor Used for Simultaneous Determination of Effective Tea Components January 24th, 2015

The latest fashion: Graphene edges can be tailor-made: Rice University theory shows it should be possible to tune material's properties January 24th, 2015

Water

Nanoparticles for clean drinking water January 17th, 2015

Going with the flow January 16th, 2015

Rice's Naomi Halas to direct Smalley Institute: Optics pioneer will lead Rice's multidisciplinary science institute January 15th, 2015

Liquids and glasses relax, too. But not like you thought January 15th, 2015

NanoNews-Digest
The latest news from around the world, FREE



  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More










ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project







© Copyright 1999-2015 7th Wave, Inc. All Rights Reserved PRIVACY POLICY :: CONTACT US :: STATS :: SITE MAP :: ADVERTISE