07/15/2025
By Suzanne Young

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

Candidate Name: Julianne Gath
Degree: Master's
Defense Date: Monday, July 28, 2025
Time: 12:30 to 2:30 p.m.
Location: Room 518, Olney Hall, North Campus

Thesis Title: “Investigating Nanoscale Interactions Between Intrinsically Disordered Proteins and Gold Nanoparticles”

Committee:

  • Matthew Gage, Ph.D., Department of Chemistry, University of Massachusetts Lowell
  • Leslie Farris, Ph.D., Department of Chemistry, University of Massachusetts Lowell
  • Advisor: Michael B. Ross, 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. In this study, interactions between IDP-derived peptides and gold colloidal nanoparticles (AuNPs) were investigated to understand how pH and peptide length influence conjugate properties. Peptides from the PEVK region of titin, specifically the glutamic acid-rich PolyE and lysine-rich PPAK motifs, were conjugated to AuNPs using a straightforward preparation approach involving pH-controlled buffers. UV-visible spectroscopy revealed clear sequence-dependent behaviors: PolyE-Au NP conjugates exhibited pronounced pH responsiveness, with significant shifts in optical absorbance indicating pH-dependent conformational changes. In contrast, PPAK-Au NP conjugates displayed limited pH sensitivity but showed measurable dependence on peptide length, with shorter sequences producing optical properties more similar to unmodified nanoparticles. Transmission electron microscopy further confirmed that both peptides stabilized well-dispersed nanoparticle conjugates without inducing aggregation. Zeta potential measurements also revealed trends related to the pH dependence of PolyE and the length dependence of PPAK. 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-Au NP assemblies for applications in drug delivery, in vivo pH sensing, and stimuli-responsive therapeutic development.