Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Tweaking a molecule's structure can send it down a different path to crystallization

18.04.2017

Insights could lead to better control of drug development, energy technologies -- and food

Silky chocolate, a better medical drug, or solar panels all require the same thing: just the right crystals making up the material. Now, scientists trying to understand the paths crystals take as they form have been able to influence that path by modifying the starting ingredient.


A small change to a peptoid that crystallizes in one step (left) sends the modified peptoid down a more complicated path from disordered clump to crystal (right).

Credit: Jim De Yoreo/PNNL

The insights gained from the results, reported April 17 in Nature Materials, could eventually help scientists better control the design of a variety of products for energy or medical technologies.

"The findings address an ongoing debate about crystallization pathways," said materials scientist Jim De Yoreo at the Department of Energy's Pacific Northwest National Laboratory and the University of Washington. "They imply you can control the various stages of materials assembly by carefully choosing the structure of your starting molecules."

From floppy to stiff

One of the simplest crystals, diamonds are composed of one atom -- carbon. But in the living world, crystals, like the ones formed by cocoa butter in chocolate or ill-formed ones that cause sickle cell anemia, are made from molecules that are long and floppy and contain a lengthy well-defined sequence of many atoms. They can crystallize in a variety of ways, but only one way is the best. In pharmaceuticals, the difference can mean a drug that works versus one that doesn't.

Chemists don't yet have enough control over crystallization to ensure the best form, partly because chemists aren't sure how the earliest steps in crystallization happen. A particular debate has focused on whether complex molecules can assemble directly, with one molecule attaching to another, like adding one playing card at a time to a deck. They call this a one-step process, the mathematical rules for which scientists have long understood.

The other side of the debate argues that crystals require two steps to form. Experiments suggest that the beginning molecules first form a disordered clump and then, from within that group, start rearranging into a crystal, as if the cards have to be mixed into a pile first before they could form a deck. De Yoreo and his colleagues wanted to determine if crystallization always required the disordered step, and if not, why not.

Clump, snap and ...

To do so, the scientists formed crystals from a somewhat simplified version of the sequence-defined molecules found in nature, a version they call a peptoid. The peptoid was not complicated -- just a string of two repeating chemical subunits (think "ABABAB") -- yet complex because it was a dozen subunits long. Based on its symmetrical chemical nature, the team expected multiple molecules to come together into a larger structure, as if they were Lego blocks snapping together.

In a second series of experiments, they wanted to test how a slightly more complicated molecule assembled. So, the team added a molecule onto the initial ABABAB... sequence that stuck out like a tail. The tails attracted each other, and the team expected their association would cause the new molecules to clump. But they weren't sure what would happen afterwards.

The researchers put the peptoid molecules into solutions to let them crystallize. Then the team used a variety of analytical techniques to see what shapes the peptoids made and how fast. It turns out the two peptoids formed crystals in very different fashions.

A tail of two steps

As the scientists mostly expected, the simpler peptoid formed initial crystals a few nanometers in size that grew longer and taller as more of the peptoid molecules snapped into place. The simple peptoid followed all the rules of a one-step crystallization process.

But thrusting the tail into the mix disrupted the calm, causing a complex set of events to take place before the crystals appeared. Overall, the team showed that this more complicated peptoid first clumped together into small clusters unseen with the simpler molecules.

Some of these clusters settled onto the available surface, where they sat unchanging before suddenly converting into crystals and eventually growing into the same crystals seen with the simple peptoid. This behavior was something new and required a different mathematical model to describe it, according to the researchers. Understanding the new rules will allow researchers to determine the best way to crystallize molecules.

"We were not expecting that such a minor change makes the peptoids behave this way," said De Yoreo. "The results are making us think about the system in a new way, which we believe will lead to more predictive control over the design and assembly of biomimetic materials."

###

This work was supported by the Department of Energy Office of Science and PNNL's Laboratory Directed Research and Development program.

Reference: Xiang Ma, Shuai Zhang, Fang Jiao, Christina Newcomb, Yuliang Zhang, Arushi Prakash, Zhihao Liao, Marcel Baer, Christopher Mundy, Jim Pfaendtner, Aleksandr Noy, Chun-Long Chen and Jim De Yoreo, Tuning crystallization pathways through sequence-engineering of biomimetic polymers. Nature Materials April 17, 2017 DOI: 10.1038/nmat4891 (In press.)

Interdisciplinary teams at Pacific Northwest National Laboratory address many of America's most pressing issues in energy, the environment and national security through advances in basic and applied science. Founded in 1965, PNNL employs 4,400 staff and has an annual budget of nearly $1 billion. It is managed by Battelle for the U.S. Department of Energy's Office of Science. As the single largest supporter of basic research in the physical sciences in the United States, the Office of Science is working to address some of the most pressing challenges of our time. For more information on PNNL, visit the PNNL News Center, or follow PNNL on Facebook, Google+, LinkedIn and Twitter.

Media Contact

Mary Beckman
mary.beckman@pnnl.gov
509-375-3688

 @PNNLab

http://www.pnnl.gov/news 

Mary Beckman | EurekAlert!

Further reports about: Nature Materials crystallization crystals peptoid

More articles from Life Sciences:

nachricht Barium ruthenate: A high-yield, easy-to-handle perovskite catalyst for the oxidation of sulfides
16.07.2018 | Tokyo Institute of Technology

nachricht The secret sulfate code that lets the bad Tau in
16.07.2018 | American Society for Biochemistry and Molecular Biology

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

Im Focus: Chemical reactions in the light of ultrashort X-ray pulses from free-electron lasers

Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.

Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

Subaru Telescope helps pinpoint origin of ultra-high energy neutrino

16.07.2018 | Physics and Astronomy

Barium ruthenate: A high-yield, easy-to-handle perovskite catalyst for the oxidation of sulfides

16.07.2018 | Life Sciences

New research calculates capacity of North American forests to sequester carbon

16.07.2018 | Earth Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>