Chiral Crystal Packing Induces Enhancement of Vibrational Circular Dichroism

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Chiral Crystal Packing Induces Enhancement of Vibrational Circular Dichroism, Angew. Chem. Int. Ed. 2018, 57, 13344 –13348

 

Vibrational circular dichroism (VCD) has enriched the toolbox of analyzing and classifying chiral supramolecular organization due to its outstanding sensitivity towards absolute and relative configurations and its ability to resolve induced chirality in originally achiral regions. Lately, VCD entered the field of amyloid fibrils that are related to neurodegenerative disorders, such as AlzheimerQs disease. The proteins exhibit strongly amplified VCD signals in the amide region, whose shape and intensity are highly sensitive to the precise fibril structure. VCD in biopolymers, such as RNA or DNA, has long been under investigation accompanied by the establishment of the powerful coupled oscillator (CO) model to empirically account for distinct spectral patterns. The COmodel has been able to relate VCD amplification in proteins to supramolecular chirality. Yet, care must be taken as, according to Kurouski et al., filament chirality is “very delicate” and “subtle” a level of protein chirality; accordingly, the CO model is given a mixed assessment.

 

 

Pour en savoir plus, consultez le communiqué de presse associé à cet article : La quête des structures chirales supramoléculaires !

 

 

Résumé: 

Angew. Chem. Int. Ed. 2018, 57, 13344 –13348

 

We demonstrate that molecular vibrations with originally low or zero intensity in a vibrational circular dichroism (VCD) spectrum attain chirality in molecular crystals by coordinated motion of the atoms. Ab initio molecular dynamics simulations of anharmonic solid-state VCD spectra of l-alanine crystals reveal how coherent vibrational modes exploit the space groupQs chirality, leading to nonlocal, enhanced VCD features, most significantly in the carbonyl region of the spectrum. The VCD-enhanced signal is ascribed to a helical arrangement of the oscillators in the crystal layers. No structural irregularities need to be considered to explain the amplification, but a crucial point lies in the polarization of charge, which requires an accurate description of the electronic structure. Delivering a quantitative atomic conception of supramolecular chirality induction, our ab initio scheme is applicable well beyond molecular crystals, for example, to address VCD in proteins and related compounds.

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Chiral Crystal Packing Induces Enhancement of Vibrational Circular Dichroism

 

Sascha Jähnigen, Arne Scherrer, Rodolphe Vuilleumier, and Daniel Sebastiani

 

Angew. Chem. Int. Ed. 2018, 57, 13344 –13348

 

DOI:10.1002/anie.201805671