The immobilization of enzymes onto nanoparticle-sized materials like hematite (a-Fe2O3) has been reported to positively affect their activity and stability. Peptides that specifically bind to a surface are useful for the functionalization of materials, as they circumvent the need for harsh cross-linking chemicals that may impair enzymatic activity. Previous studies have illustrated that introducing peptide sequences with novel hematite affinity into biotechnologically relevant enzymes can increase their effectiveness. Optimizing the interactions between hematite and small peptides could lead to further advances in how enzymes are put to work in medicine and technology. In this study, two small hematite-binding peptides were empirically designed and synthesized, and their affinity for hematite was tested by atomic force microscopy. One of these peptides contained no threonine residues (HSSSSYSPS), while the other contained two threonine residue substitutions (HTSSTYSPS). These peptides were immobilized on a self-assembled monolayer (SAM) and probed with a hematite-coated AFM tip. By analyzing force spectra with the worm-like chain model, we determined the on-rate constant (kon), off-rate constant (koff), and dissociation constant (Kd) for both peptides. At loading rates between 104 and 106 pN/sec, the koff and Kd for the threonine-containing peptide was approximately double that of the serine-only peptide, indicating that the serine-only peptide bound twice as strongly to a hematite surface. This distinction is likely attributed to structural differences between serine and threonine, and serine is able to “screen” surface charge more effectively than threonine.

Exploring the influence of amino acid strucutre on interactions between peptides and hematite surfaces

255th National Meeting (2018)

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