Interfacial Behaviors of Antimicrobial Peptide Cecropin P1 Immobilized on Different Self-Assembled Monolayers

Abstract

Surfaces immobilized with biological molecules such as peptides and proteins are widely used in many important applications including biosensors, medical devices, and food packaging. It was found that the structures of surface-immobilized peptides control their surface properties. In this study, we investigated interfacial behaviors of antimicrobial peptide cecropin P1 (CP1) immobilized onto a maleimide-terminated self-assembled monolayer (Mal SAM) and a mixed SAM (Mal-OH SAM, a mixture of maleimide-terminated SAM and hydroxyl-terminated SAM) surface via C-terminus modified cysteine (CP1c). The surface coverage, secondary structure, orientation, and antimicrobial activity of immobilized CP1c were investigated using surface plasmon resonance (SPR), circular dichroism (CD), sum frequency generation (SFG) vibrational spectroscopy, dynamic contact antimicrobial assay, and coarse grained molecular dynamics (MD) simulations. It was found that the surface coverages of CP1c on the Mal SAM and the mixed Mal-OH SAM are similar. CP1c on Mal SAM possessed a dominant helical structure with a single orientation of ∼32° versus surface normal. CP1c on Mal-OH mixed SAM surface also possessed a dominant helical structure but with multiple orientations. MD simulation results can be correlated to the experimental data: the simulation results indicate a narrow distribution of orientations of CP1c immobilized on Mal SAM, but multiple orientations are sampled on the more hydrophilic Mal-OH SAM. Even though the surface orientations of CP1c immobilized on the two SAM surfaces are different, activity against both Gram-negative and Gram-positive bacteria (Escherichia coli and Staphylococcus aureus) exhibited similar results for CP1c immobilized on both SAM surfaces. We believe that this is because the antimicrobial activity of the surface-immobilized peptides is mainly affected by the electrostatic interactions between the strong basic N-terminal residues and the negatively charged bacteria cell wall/cell membrane.

Investigating the Effect of Two-Point Surface Attachment on Enzyme Stability and Activity

“…More detailed procedures of SAM surface preparation and biomolecules immobilization have been published previously. 66 The schematic showing the SAM preparation and enzyme immobilization can be found in the Supporting Information (Figure S3).…”

“…Before characterization, the substrates were washed with DI water, 1% sodium dodecyl sulfate (SDS) solution, and DI water for a second time, to remove any physically adsorbed NfsB enzymes. More detailed procedures of SAM surface preparation and biomolecules immobilization have been published previously . The schematic showing the SAM preparation and enzyme immobilization can be found in the Supporting Information (Figure S3).…”

“…This model employed the Karanicolas and Brooks Go-like protein model − and a corresponding surface potential that quantitatively describes surface hydrophobicity. Several studies have demonstrated the accuracy of predictions from this model for protein conformation and orientation while interacting with various sensor surfaces. ,,,,,− The detailed surface potential and various parameters were developed and published in earlier works , and are included in the Supporting Information for completeness. The simulation details are also described in the Supporting Information.…”

Antibacterial Properties of Triethoxysilylpropyl Succinic Anhydride Silane (TESPSA) on Titanium Dental Implants

“…Over the last years, various therapeutic strategies have been proposed to combat bacterial infections related to dental implants [12,21,22], such as the covalent immobilization of antibacterial molecules onto the surface to obtain a stable bioactive coating [23][24][25]. For this purpose, self-assembled monolayers (SAMs) of organic molecules may serve as an anchor for subsequent attachment of biomolecules [26][27][28][29].…”

Exploring Protein–Nanoparticle Interactions with Coarse‐Grained Protein Folding Models

“…We built a simple coarse‐grained model to study protein–NP interactions. Our model builds on the KB G‐like protein model and a protein–flat surface force field, the latter of which has been successfully applied in several cases to predict protein or peptide behavior of SAM biosensors . Our work represents a significant step toward a quantitative model to explore protein structure, energetics, and function on spherical NPs, as it captures both the surface curvature of the NP and the surface chemistry that influences protein–NP interactions (e.g., the hydrophobic effect).…”