Effect of Secondary Structure on Surface Adsorption of Peptides

• Author / Creator

  Binazadeh, Mojtaba

• Protein adsorption at the biomaterial-tissue interface has several detrimental consequences which undermines the widespread application of engineered materials. Herein, it was asked what role protein secondary structures play in the adsorption of peptides, as well as how these structures affect the physicochemical properties of the final adsorbed layer on bare gold (Au) and poly (ethylene glycol) (PEG) modified Au surfaces. To this end, α-helices and -sheets were induced in poly-L-Lysine (PLL) and persistence of these structures in solution and adsorbed state was confirmed by circular dichroism (CD). PLL adsorption to Au surfaces was monitored using quartz crystal microbalance with dissipation (QCM-D). PLL adsorption on bare Au resulted in higher initial adsorption rates for α-helices as compared to β-sheets but the final adsorbed amount of β-sheets was higher than α-helices regardless of solution salt concentration. Viscosities for films formed from α-helices were ~2x that of β-sheets films, regardless of solution ionic strength. β-sheets have higher zeta potential as compared to α-helices. The interaction energy between PLL and Au surface was found to be driven by electrostatic and van der Waals forces. Presence of PEG grafted brush layers on the Au surface drastically reduced the adsorbed amount of different PLL structures and PLL layers adsorbed on PEG coated surfaces had similar layer viscosities.
  To further understand PLL adsorption mechanism and adsorbed layer properties, the interacting forces between PLL-Au, PLL-PLL, PEG-mica, and PEG-PLL surfaces were studied by surface forces apparatus (SFA). SFA results revealed that the adhesion energy of β-sheet vs. Au and β-sheet vs. β-sheet was considerably more than α-helix vs. Au and α-helix vs. α-helix systems respectively. The substrate surface adhesion energy of β-sheet was more dependent on the solution salt concentration as compared to α-helix due to the higher electrostatic interactions of β-sheet PLL film with Au (higher zeta potential value of β-sheet PLL). It was found that presence of PEG grafted layer eliminated the PLL secondary structure effect on adsorption due to the purely repulsive force that governed the PEG vs. PLL interaction.

• Subjects / Keywords

  • Surface Adsorption
  • Peptides
  • Secondary Structure

• Graduation date

  Fall 2013

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3X34N11K

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.