Infrared spectrum and structure of the homochiral serine octamer–dichloride complex


The amino acid serine is known to form a very stable octamer that has properties that set it apart from serine complexes of different sizes or from complexes composed of other amino acids. For example, both singly protonated serine octamers and anionic octamers complexed with two halogen ions strongly prefer homochirality, even when assembled from racemic D,L mixtures. Consequently, the structures of these complexes are of great interest, but no acceptable candidates have so far been identified. Here, we investigate anionic serine octamers coordinated with two chloride ions using a novel technique coupling ion mobility spectrometry–mass spectrometry with infrared spectroscopy, in combination with theoretical calculations. The results allow the identification of a unique structure for (Ser8Cl2)2− that is highly symmetric, very stable and homochiral and whose calculated properties match those observed in experiments.

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Figure 1: IMS-MS of serine cluster anions.
Figure 2: Size- and conformer-selected infrared spectra of serine cluster–dichloride complexes.
Figure 3: Theoretical structure of the homochiral serine octamer–dichloride complex.


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The authors acknowledge the expert assistance of the FHI free electron laser facility staff, in particular S. Gewinner and W. Schöllkopf. M.T.B. acknowledges the Alexander von Humboldt Foundation and the National Science Foundation (USA) for support under grants CHE-1301032 and CHE-1565941.

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J.S., S.W., K.P., M.T.B. and G.v.H. conceived and designed the experiments. J.S. and S.W. performed the experiments. J.S. analysed the data and suggested the structure of the serine octamer with two chlorides. All authors co-wrote the paper.

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Correspondence to Jongcheol Seo or Gert von Helden.

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The authors declare no competing financial interests.

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Seo, J., Warnke, S., Pagel, K. et al. Infrared spectrum and structure of the homochiral serine octamer–dichloride complex. Nature Chem 9, 1263–1268 (2017).

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