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Vibrational Circular Dichroism Shows Reversible Helical Handedness Switching in Peptidomimetic lValine Fibrils

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  1. 1. Vibrational Circular Dichroism Shows Reversible Helical HandednessSwitching in Peptidomimetic L‑ Valine Fibrils. Belén Nieto-Ortega,† Vicent J. Nebot,‡ Juan F. Miravet,‡ TOC Graphics Beatriu Escuder,‡ Juan T. López Navarrete,† Juan Casado,† and Francisco J. Ramírez*,† †Departamento de Química Física, Facultad de Ciencias, Universidad de Málaga, Málaga 29071, Spain ‡Department de Química Inorgànica I Orgànica, Universitat Jaume I, Castellón 12071, SpainJ. Phys. Chem. Lett. 2012, Vol.3, 2120 -2124 1
  2. 2. Carbohydrates Proteins DNA Many of the most relevant physical and chemical phenomena in Nature depend on the supramolecular organization of the matter around us α-Helix Fibrillation process - pH can be mimicked in laboratory - Ionic strength experiments by - Concentration gelation of short - Temperature peptides in water Fibers β-SheetProprietary and Confidential 2 American Chemical Society
  3. 3. Objective: L-Valine Elucidate the peptidomimetic supramolecular compound organization (Pval) L-Valine L-Valine Pyridyl Trimethylene bridge Pyridyl In this work, the structural organization into fibrils of Pval3 gels has been followed by: Proprietary and Confidential 3 American Chemical Society
  4. 4. VCD chiro-optical spectra of the Pval3. D2O, 18mM 1800-1500 cm-1 pD=6.0-3.0Amide I mode pD=2.3 pD=2.0 Amide II mode Wavenumber / cm-1 This process is reversible restoring the pD Proprietary and Confidential 4 American Chemical Society
  5. 5. VCD chiro-optical spectra of the Pval3. D2O, 18mM Presence of strong intermolecular C=O···H−N hydrogen bonds. Non-inversion Pyridine are not involved pD=6.0-3.0 in the supramolecular pD=2.3 organization. pD=2.0 Wavenumber / cm-1 Mirrorlike VCD response with lowering pD Proprietary and Confidential 5 American Chemical Society
  6. 6. ECD chiro-optical spectra of the Pval3. D2O, 18mM pD=6.0-3.0 pD=2.3 pD=2.0 The spectrum at 2.0 shows slight differences. α-helix intensity band is lower Pyridine rings n→π* Slight change in the Supramolecular secondary structure transition supported is required by the VCD spectra Proprietary and Confidential 6 American Chemical Society
  7. 7. SEM and AFM images of the Pval3. D2O, 18mM pD=6.0-3.0 pD=2.3 pD=2 Proprietary and Confidential 7 American Chemical Society
  8. 8. VCD and ECD spectra by changing ionic strength Adding NaCl, I = 0.002M Mirrow images No relevant changesProprietary and Confidential 8 American Chemical Society
  9. 9. Conclusions - The complete self-assembly process of a low molecular mass hydrogelator, Pval3, has been scrutinized by vibrational circular dichroism. Jaume I University -In this paper, we show a nice example of the versatility of the VCD spectroscopy. 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 Málaga University change in the handedness of the helix by modulating different external stimuli as pD or ionic strength. Therefore this paper provides the first observation by VCD of such a phenomenon in a short peptide. Acknowledgments This work was supported by the Ministerio de Educación (projects CTQ2009-10098 and CTQ2009-13961, and the grant AP2009-2797 to BNO) and the Junta de Andalucía (Project P09-FQM-4708).Proprietary and Confidential 9 American Chemical Society