Dimer Is Not Double: The Unexpected Behavior of Two-Floor Peptide Nanosponge

Area of Science:

• Biomaterials Science
• Surface Chemistry
• Peptide Self-Assembly

Background:

• Investigating stimuli-responsive behavior of peptide assemblies on solid surfaces.
• Utilizing a modified dimeric antimicrobial peptide (Trichogin GAIV analog) chemisorbed onto a gold surface via a lipoic acid N-terminus.

Purpose of the Study:

• To understand the pH-responsive behavior of a chemisorbed dimeric peptide assembly.
• To elucidate the molecular mechanisms behind observed macroscopic changes in the peptide layer.

Main Methods:

• Quartz Crystal Microbalance with Dissipation monitoring (QCM-D)
• Surface Plasmon Resonance (SPR)
• Nanoplasmonic Sensing (NPS)
• Fourier-Transform Infrared Spectroscopy (FTIR)
• Molecular Dynamics (MD) simulations

Main Results:

• Observed pH-driven squeezing behavior (thickness and mass variations) attributed to lysine residue hydrophilicity/hydrophobicity changes.
• Identified hysteresis in response to pH cycling, linked to conformational rearrangements (helix to beta sheets) in the peptide layer.
• Dimeric assembly exhibits unique properties, not merely a doubling of monomer behavior.

Conclusions:

• The dimeric peptide assembly demonstrates distinct pH-responsive characteristics.
• Lysine protonation state significantly influences peptide layer mass and thickness.
• Conformational dynamics, particularly near the surface, are crucial for the observed hysteresis and unique dimeric behavior.