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In­no­va­ti­on in Decoding Complex Molecular Structures

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Two men stand in a laboratory. © Clever Lab​/​TU Dort­mund
Dr. Julian Holstein and Prof. Guido Clever presented their in­ter­na­tio­nal re­search proj­ect in Nature Reviews Chem­is­try.

Dr. Julian Holstein and Prof. Guido Clever from the Department of Chem­is­try and Chemical Biology at TU Dort­mund Uni­ver­sity are working with sci­en­tists from the Uni­ver­sity of Vienna to establish a method to elucidate complex molecular structures more quickly and easily. Instead of X-ray photons – which are normally used to determine the structures – electrons are diffracted on the crystal. This means that even tiny crystals of a substance under examination can now be used. The in­ter­na­tio­nal re­search proj­ect has now been presented as the cover story in the re­nowned journal Nature Reviews Chem­is­try.

Molecular structures are usually determined using X-ray diffraction on single crystals. This method makes it possible to establish the three-dimensional structure of complex substances in the crystal lattice and derive a wide range of in­for­mation, such as the arrangement of the atoms and the expected chemical reactivity of the compound. X-ray diffraction is therefore the standard method of characterizing unknown substances. The challenge here is that the crystals of the substances under examination must be of a suitable size. This is why researchers often fail to determine a substance’s structure.

New method reduces sample size requirements

With electron crystallography, on the other hand, electrons are diffracted on the crystal instead of X-ray photons. “What makes this method special is that we can use tiny, crystalline particles with sizes in the range of 100-1000 nanometers,” says Dr. Julian Holstein, who is the correspondent author of the article alongside Dr. Tim Grüne from the Uni­ver­sity of Vienna. As a result, powdery, crystalline deposits, which can often even be found in raw products that are still contaminated, become accessible as samples. These particles cannot be seen with the naked eye or even with extremely powerful optical microscopes. “Even samples that are unsuitable for high-brilliance synchrotron radiation due to their small crystal size can be examined using electron diffraction. Due to less stringent demands on sample size, we are also able to shorten the very time-consuming crystallization processes in the laboratory,” adds Dr. Julian Holstein. As a result, this method also has a lot of interesting potential for other scientific areas such as materials science or pharmacy.

The cover of the magazine "nature reviews chemistry" and electrons are diffracted. © Julian J. Holstein & Shota Hasegawa​/​TU Dort­mund Uni­ver­sity; Design: Carl Conway.
The cover of the magazine Nature Reviews Chem­is­try: The electron diffraction method opens up new avenues to determine complex mol­ecules using microscopically small crystals.

Hydrogen atoms can be recognized more easily

Electron diffraction also offers yet another advantage. Using this method, very light hydrogen atoms, which often play a key role in both chemical reactions and biological processes, can be detected particularly effectively. What’s more, the oxidation state of certain elements in the crystal can be experimentally determined, which was previously not possible. This opens up new re­search opportunities in the field of catalyst re­search, hydrogen storage and drug development.

Prof. Guido Clever, Professor of Bioinorganic Chem­is­try at TU Dort­mund Uni­ver­sity and one of the authors of the proj­ect says: “We are enthusiastic about the results of the measurements we carried out on our samples at ETH Zurich and the Uni­ver­sity of Vienna. We are confident that this method can lead to a series of previously inaccessible results in the areas of functional mol­ecules and materials, solvation science and drug re­search.”

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