SEARCH

SEARCH BY CITATION

Keywords:

  • Fourier-transform Raman spectroscopy (FT-RS);
  • Fourier-transform infrared (FT-IR) spectroscopy;
  • surface-enhanced Raman scattering (SERS);
  • density functional theory (DFT);
  • L-valine phosphonate dipeptides

Abstract

Four L-valine (L-Val) phosphonate dipeptides that are potent inhibitors of zinc metalloproteases, namely, L-Val-C(Me)2-PO3H2 (V1), L-Val-CH(iP)-PO3H2 (V2), L-Val-CH(iB)-PO3H2 (V3), and L-Val-C(Me)(iP)-PO3H2 (V4), are studied by Fourier-transform infrared (FT-IR) spectroscopy, Fourier-transform Raman spectroscopy (FT-RS), and surface-enhanced Raman scattering (SERS). The band assignment (wavenumbers and intensities) is made based on (B3LYP/6-311 + + G**) calculations. Comparison of theoretical FT-IR and FT-RS spectra with those of SERS allows to obtain information on the orientation of these dipeptides as well as specific-competitive interactions of their functionalities with the silver substrate. More specifically, V1 and V4 appear to interact with the silver substrate mainly via a [BOND]CsgCH3 moiety localized at the [BOND]NamideCsg(CH3)P[BOND]molecular fragment. In addition, the [BOND]POH and isopropyl units of V4 assist in the adsorption process of this molecule. In contrast, the [BOND]CαNH2 and [BOND]PO3H groups of V2 and V3 interact with the silver nanoparticles, whereas their isopropyl and isobutyl fragments seem to be repelled by the silver substrate (except for the [BOND]CH2 [BOND] of V3), similar to the [BOND]Cβ(CH3)2 fragment of L-Val for all L-Val phosphonate dipeptides investigated in this work. The adsorption mechanism of these molecules onto the colloidal silver surface is also affected by amide bond behavior. Copyright © 2010 John Wiley & Sons, Ltd.