Vibrational Circular Dichroism Shows Reversible Helical Handedness Switching in Peptidomimetic l‑Valine Fibrils

We elucidate the supramolecular organization in the form of microsize fibrils of gels formed by a l-Valine peptidomimetic compound. Analysis was based on circular dichroism spectroscopies, vibrational (VCD) and electronic (CD), supported by microscopy (atomic force and scanning electron). We show how the VCD spectra give account of the micrometric structure of the fibrils formed by the helicoidal arrangement of simpler proto-fibrils, which are organized in a lower hierarchical level. This ability is used to monitorize a fully reversible change in the handedness of the helix by modulating different external stimuli as pH or ionic strength, thus providing the first observation by VCD of such a phenomenon in a short peptide

Mode Robustness in Raman Optical Activity

By reformulating Raman and ROA invariants we provide ground for the definition of robust modes in ROA spectroscopy. Introduction of two parameters defining robustness helps characterization and assignment of ROA bands. Application and use of robustness parameters to [<i>n</i>]­helicenes and oxirane/thiirane derivatives are presented