04/02/2026
By Michael Brown

The Kennedy College of Sciences, Department of Chemistry, invites you to attend a Masters thesis defense by Julianne Gath on “Investigating Nanoscale Interactions Between Intrinsically Disordered Proteins and Gold Nanoparticles.”

Candidate Name: Julianne Gath
Degree: Masters
Defense Date: Friday, April 10, 2026
Time: 12:30 to 2:30 p.m.
Location: Room 520, Olney Hall, North Campus
Thesis Title: “Investigating Nanoscale Interactions Between Intrinsically Disordered Proteins and Gold Nanoparticles”

Committee:

  • Advisor: Michael B. Ross, Ph.D., Department of Chemistry, University of Massachusetts Lowell
  • Matthew Gage, Ph.D., Department of Chemistry, University of Massachusetts Lowell
  • Leslie Farris, Ph.D., Department of Chemistry, University of Massachusetts Lowell

Abstract

Intrinsically disordered proteins (IDPs) are a unique class of biomolecules that lack stable tertiary structure under physiological conditions. This inherent flexibility enables them to adopt diverse conformations in response to environmental cues, making them ideal candidates for nanoscale biomedical applications. This study investigates how peptide sequence, length, and pH influence interactions between IDP-derived peptides and gold nanoparticles (AuNPs). Peptides from the PEVK region of titin, specifically the glutamic acid-rich PolyE and lysine-rich PPAK motifs, were conjugated to AuNPs using pH-controlled buffers and freeze-thaw preparation methods. UV-visible spectroscopy revealed distinct sequence-dependent behavior. PolyE-AuNP conjugates exhibited strong pH responsiveness, with red shifts and peak broadening under acidic conditions. In contrast, PPAK-AuNP conjugates showed minimal pH sensitivity but a clear dependence on peptide length, where shorter sequences behaved similarly to unmodified AuNPs. Transmission electron microscopy confirmed that both peptides form well-dispersed conjugates without significant aggregation. Zeta potential measurements supported these trends, showing reduced negative surface charge for PolyE at low pH, while PPAK displayed charge variation without corresponding optical changes. These findings demonstrate that both sequence composition and structural parameters critically affect IDP-nanoparticle interactions. While preliminary, this work provides insight into the design of responsive nanomaterials and highlights the potential of IDP-AuNP assemblies for applications in drug delivery, in vivo pH sensing, and stimuli-responsive therapeutic development.