Structural properties of hydration shell around various conformations of simple polypeptides

Area of Science:

• Computational chemistry and biophysics
• Investigating molecular interactions and solvation dynamics
• Understanding peptide-water systems

Background:

• The solvation shell of peptides influences their structure and function.
• Quantifying water ordering around peptides is crucial for understanding these interactions.
• Previous studies have explored various aspects of peptide solvation.

Purpose of the Study:

• To develop a rational measure for water structural ordering within peptide solvation shells.
• To investigate the structural and dynamic properties of water around different peptide secondary structures.
• To compare the solvation behavior of alanine-based and glycine-based polypeptides.

Main Methods:

• Utilizing the two-particle contribution to entropy to quantify water ordering.
• Employing harmonic approximation for entropy estimation.
• Analyzing hydrogen bond network geometry, self-diffusion coefficients, and hydrogen bond lifetimes.
• Developing an ordering map based on translational, configurational, and orientational ordering.

Main Results:

• Water structure in the solvation shell changes slightly compared to bulk water.
• A novel parameter effectively measures local water ordering, factoring into translational, configurational, and orientational components.
• A pseudorigid water
• halo
• forms around peptides, with longer water-water hydrogen bond lifetimes and increased stability.
• Alanine peptides exhibit distinct solvation behavior compared to glycine peptides due to methyl group interactions and increased solvation layer rigidity.

Conclusions:

• The proposed water ordering parameter provides deeper insight into solvation shell properties.
• Local water ordering correlates with the relative stability of peptide secondary structures.
• Peptide secondary structures, particularly helices, create a distinct solvation environment.
• Significant differences in solvation layer dynamics and interactions exist between alanine and glycine peptides, impacting their behavior in aqueous solutions.