Influence of Sulfoxide Group Placement on Polypeptide Conformational Stability

Area of Science:

• Polymer Chemistry
• Biophysical Chemistry
• Materials Science

Background:

• Studying polypeptide secondary structures like helix-coil transitions is crucial for understanding protein folding and function.
• Existing models often face challenges with water solubility, charged group interference, or phase separation, complicating in-water analyses.
• Nonionic, water-soluble models are needed to isolate and study the intrinsic conformational behavior of polypeptides.

Purpose of the Study:

• To synthesize and characterize a homologous series of novel nonionic sulfoxide-containing polypeptides.
• To investigate the influence of sulfoxide groups on polypeptide water solubility and conformational behavior in aqueous solutions.
• To establish a model system for studying helix-coil transitions in water without confounding factors.

Main Methods:

• Synthesis of five new nonionic sulfoxide-containing polypeptide homologues.
• Characterization of synthesized polypeptides, including assessment of water solubility.
• Analysis of polypeptide chain conformations in water using techniques sensitive to secondary structure (e.g., spectroscopy, viscometry).
• Systematic variation of sulfoxide proximity to the backbone and side-chain length to probe conformational determinants.

Main Results:

• Successful synthesis of five novel nonionic sulfoxide-containing polypeptides with inherent water solubility.
• Demonstrated that sulfoxide groups confer water solubility, enabling their use in aqueous studies.
• Observed that polypeptide chain conformations in water are dependent on the distance of sulfoxide groups from the backbone, side-chain length, and solvent conditions.
• Established a correlation between molecular structure and observed chain conformations.

Conclusions:

• Nonionic sulfoxide polypeptides provide a versatile platform for studying aqueous polypeptide behavior.
• The conformational preferences of these polypeptides can be tuned by structural modifications, offering control over secondary structure.
• These findings facilitate the design of polypeptide segments with specific conformations for structural and functional applications in biophysics and materials science.