Sunscreen for dancing molecules

August 01, 2018

Since life is mostly based on water, our molecules are moving, vibrating and somersaulting in a liquid environment. But electron microscopy, a superb instrument to study a static version of the nanoworld, has been almost impossible to use to see moving molecules because the incident electron beam damages the samples. Scientists at the Center for Soft and Living Matter, within the Institute for Basic Science (IBS), now report a big improvement. This study, published in ACS Nano, is the first to use heavy water (D2O) - a form of water that contains deuterium (D) instead of hydrogen - in the field of transmission electron microscopy (TEM). This approach significantly delays sample damage, which is one of the major impediments for broader application of liquid-phase TEM to fragile biological samples.

In electron microscopy, electrons shot against the sample have a much shorter wavelength than light, so they are better suited to provide information about single molecules. On the other hand, the electron beam is violently strong and risks damaging the specimen due to its high energy, which generates an electric charge and breaks the chemical bonds. 

IBS researchers used a tiny pocket filled with liquid sandwiched between atomically-thin sheets of graphene, within which the sample molecules are free to move and are protected from electrical charging, and tested several types of liquids to find the one that preserves the sample longer. "In contrast to the common approach of reducing the energy of the electron beam to delay sample damage, we focused on tuning the environment; the water in which the molecules of interest are dissolved," says Huan Wang, co-author of the study. 

IBS scientists have shown that use of heavy water has several advantages over competing methods. D2O delays most effectively not only the formation of gas bubbles, but also structural damage of individual polymer molecules. Compared to H2O, D2O has one more neutron, which means that it is heavier, thus more difficult to dissociate into radicals, and less reactive in the subsequent damaging process.

"Heavy water outperforms the competing methods by a factor of two to five at least," specified Kandula Hima Nagamanasa, co-author of the study. "Since bubble formation is delayed, and the molecules were visible for twice as long." 

An equally important advantage is that D2O is a harmless sunscreen. The sample, a polymer of polystyrene sulfonate in this case, showed the same pattern of dynamics and similar contrast in D2O and in water. 

"In the future, we plan to extend this study to more complex macromolecules, like DNA and proteins," explained Steve Granick, director of the IBS center and corresponding author of the study. "Moreover, the study opens avenues to observe long-term phenomena in other related microscopy techniques, like cryoEM (cryogenic electron microscopy), and to get more statistical information about complex phenomena, like self-assembly of single molecules into more complex biological structures."
-end-


Institute for Basic Science

Related Molecules Articles from Brightsurf:

Finally, a way to see molecules 'wobble'
Researchers at the University of Rochester and the Fresnel Institute in France have found a way to visualize those molecules in even greater detail, showing their position and orientation in 3D, and even how they wobble and oscillate.

Water molecules are gold for nanocatalysis
Nanocatalysts made of gold nanoparticles dispersed on metal oxides are very promising for the industrial, selective oxidation of compounds, including alcohols, into valuable chemicals.

Water molecules dance in three
An international team of scientists has been able to shed new light on the properties of water at the molecular level.

How molecules self-assemble into superstructures
Most technical functional units are built bit by bit according to a well-designed construction plan.

Breaking down stubborn molecules
Seawater is more than just saltwater. The ocean is a veritable soup of chemicals.

Shaping the rings of molecules
Canadian chemists discover a natural process to control the shape of 'macrocycles,' molecules of large rings of atoms, for use in pharmaceuticals and electronics.

The mysterious movement of water molecules
Water is all around us and essential for life. Nevertheless, research into its behaviour at the atomic level -- above all how it interacts with surfaces -- is thin on the ground.

Spectroscopy: A fine sense for molecules
Scientists at the Laboratory for Attosecond Physics have developed a unique laser technology for the analysis of the molecular composition of biological samples.

Looking at the good vibes of molecules
Label-free dynamic detection of biomolecules is a major challenge in live-cell microscopy.

Colliding molecules and antiparticles
A study by Marcos Barp and Felipe Arretche from Brazil published in EPJ D shows a model of the interaction between positrons and simple molecules that is in good agreement with experimental results.

Read More: Molecules News and Molecules Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.