Characterizing Interactions Between Small Peptides and Dimethyl Sulfoxide Using Infrared Spectroscopy and...

Area of Science:

• Biophysical Chemistry
• Computational Chemistry
• Spectroscopy

Background:

• Understanding solvent-peptide interactions is crucial for predicting peptide behavior in biological systems.
• Dimethyl sulfoxide (DMSO) is a common co-solvent used in peptide research, but its precise interaction mechanism with peptides remains incompletely understood.
• Small peptides serve as model systems for studying fundamental peptide-solvent interactions.

Purpose of the Study:

• To elucidate the interaction mechanisms between dimethyl sulfoxide (DMSO) and two small model peptides: diglycine and N-acetyl-glycine-methylamide (NAGMA).
• To investigate how DMSO influences the hydration shells and hydrogen bonding networks of these peptides in aqueous solutions.
• To determine if DMSO directly binds to peptides or indirectly affects them through modulation of water structure.

Main Methods:

• Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectroscopy was employed to study peptide-solvent interactions.
• Density Functional Theory (DFT) calculations, including DFT/ONIOM methods, were used to model the interactions at a molecular level.
• Analysis of HDO spectra allowed for the isolation and characterization of water molecules influenced by both peptide and DMSO.

Main Results:

• FTIR and DFT results indicated no direct chemical bonding between DMSO and the studied peptides.
• DMSO was found to indirectly influence peptide hydration shells by altering the hydrogen bonding of surrounding water molecules.
• In the diglycine system, DMSO strengthened water hydrogen bonds in the peptide's hydration sphere.
• DMSO exhibited a more moderate effect on NAGMA's hydration shell, slightly weakening hydrogen bonds due to similarities in hydration structures.

Conclusions:

• DMSO's influence on peptide hydration and stability is indirect, mediated by changes in the surrounding water structure.
• The effect of DMSO on peptide hydration shells is differential, depending on the specific structural characteristics and hydration properties of the peptide.
• These findings highlight the importance of considering solvent-mediated interactions in understanding peptide behavior and stability.