This presentation has been moved. To view this presentation, please visit http://pubs.acs.org/iapps/liveslides/pages/index.htm?mscNo=jz300725d Vibrational Circular Dichroism Shows Reversible Helical Handedness Switching in Peptidomimetic lValine Fibrils

1. Vibrational Circular Dichroism Shows
Reversible Helical Handedness
Switching 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, Spain
J. Phys. Chem. Lett. 2012, Vol.3, 2120 -2124 1

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-Sheet
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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:
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4. VCD chiro-optical spectra of the Pval3. D2O, 18mM
1800-1500 cm-1
pD=6.0-3.0
Amide I mode pD=2.3
pD=2.0
Amide II mode
Wavenumber / cm-1
This process is reversible restoring the pD
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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
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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
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7. SEM and AFM images of the Pval3. D2O, 18mM
pD=6.0-3.0 pD=2.3 pD=2
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8. VCD and ECD spectra by changing ionic strength
Adding NaCl, I = 0.002M
Mirrow images
No relevant changes
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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).
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