Hydrogen Bonding and Solvation of a Proline-Based Peptide Model in Salt Solutions

• Published in: Life (Basel, Switzerland) Vol. 11; no. 8; p. 824
• Main Authors: Catalini, Sara, Rossi, Barbara, Tortora, Mariagrazia, Foggi, Paolo, Gessini, Alessandro, Masciovecchio, Claudio, Bruni, Fabio
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 12-08-2021; MDPI
• Subjects: Anions; Aqueous solutions; Carbonyl compounds; Carbonyls; Cations; Chemical bonds; Circular dichroism; Dichroism; Equilibrium; Fluoride; Fluorides; Hydration; Hydrogen; Hydrogen bonding; Hydrogen bonds; Investigations; peptide; Peptides; Polypeptides; Proline; Protein folding; Radiation; Raman spectroscopy; Saline solutions; Selectivity; Solvation; Spectrum analysis; UV resonance Raman; Water chemistry; proline; UV resonance Raman; hydrogen bonding; peptide
• ISSN: 2075-1729; 2075-1729
• DOI: 10.3390/life11080824

The hydrogen bonding of water and water/salt mixtures around the proline-based tripeptide model glycyl-l-prolyl-glycinamide·HCl (GPG-NH
) is investigated here by multi-wavelength UV resonance Raman spectroscopy (UVRR) to clarify the role of ion-peptide interactions in affecting the conformational stability of this peptide. The unique sensitivity and selectivity of the UVRR technique allow us to efficiently probe the hydrogen bond interaction between water molecules and proline residues in different solvation conditions, along with its influence on
to
isomerism in the hydrated tripeptide. The spectroscopic data suggest a relevant role played by the cations in altering the solvation shell at the carbonyl site of proline
, while the fluoride and chloride anions were found to promote the establishment of the strongest interactions on the C=O site of proline. This latter effect is reflected in the greater stabilization of the
conformers of the tripeptide in the presence of these specific ions. The molecular view provided by UVRR experiments was complemented by the results of circular dichroism (CD) measurements that show a strong structural stabilizing effect on the β-turn motif of GPG-NH
observed in the presence of KF as a co-solute.