Although the physical reason for pPII-preference of alanine is still a matter of debate, many results emphasize the role of water.  If peptide solvation directly affects residue propensity one would expect perturbations of the hydration shell to destabilize pPII. To explore the impact sodium salts have on the conformation preference of trialanine, we used a combination of vibrational spectroscopies (IR, VCD, Raman) as well as temperature dependent UVCD.  Vibrational data were analyzed using a superposition of 2D-Gaussian functions in Ramachandran space representing subensembles of pPII, �-strand, helical, and turn conformations.  The thus obtained ensembles indicate that the pPII distribution is drastically changed upon addition of NaF salt. The temperature dependence of ?e215nm was analyzed using a two-state pPII?� thermodynamic model.  Interestingly, our results show that a rather modest amount of NaF significantly influences the conformational distribution of trialanine as well as the thermodynamics and hence the energy landscape.

Perturbing the hydration shell: Effect of salt on the conformational distribution of trialanine

244th National Meeting (2012)

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