Chemists from Radboud University Nijmegen and the Foundation for Fundamental Research on Matter (FOM) have succeeded in producing detailed 3D structures of selected peptides -- the building blocks of proteins. To do this, they worked with far-infrared light produced by Radboud University Nijmegen's laser FELIX, in use since 2013. The results, published online on 27 February in Angewandte Chemie, are important for all the follow-up research on the structure elucidation of peptides and other classes of molecules.
Physical chemists study the properties of molecules using a technique in which cooled molecules, isolated from their surroundings, are radiated with infrared light of varying frequencies. The result is a unique fingerprint of the structure of the molecule -- the infrared spectrum. The Nijmegen chemists also did this but, for the first time, using far-infrared light -- light with a wavelength of up to 0.1 millimetres. The result was a much more detailed infrared spectrum. Angewandte Chemie highlights the publication as a "very important paper," and fellow researchers from all over the world are eager to work with the methods described.
Familiar peptides, new results
The free electron laser in the FELIX lab at Radboud University Nijmegen is one of the few lasers in the world capable of producing light in the far-infrared region. Anouk Rijs, assistant professor at the Department of Molecular and Biophysics, was responsible for the research into common peptides in the human body. Although much is already known about these peptides, important new information can now be added. 'What is new about our far-infrared spectrum is that we have obtained insights in the folding of the peptides in much more detail, as well as which interactions play a role in this. This is important, for instance, for research into interactions between medicines and molecules in the body. Without far-infrared light it is not possible to obtain such detailed information about the molecular structure.'
Chemists normally determine the molecular structure by comparing the measured infrared spectrum with theoretically predicted spectra. However, the new method produced so much more detail that the old theories and mathematical models were inadequate. 'We therefore needed to develop new methods, which we did with colleagues from France,' explains Rijs. 'Using all this new information, we were able to produce an accurate 3D model of the peptides. The next step will be to study larger and more complex molecules.'
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