11/22/2024
By Kwok Fan Chow

The Kennedy College of Science, Department of Chemistry, invites you to attend a Ph.D. research proposal defense by Liyunzi Liang titled, “Exploring the Sources and Impacts of Charge Heterogeneity with Two Therapeutic Protein Models.”

Date: Wednesday, Dec. 4
Time: 3 p.m.
Location: Perry Hall, Room 415

Committee Members:
Jin Xu (Chair), Ph.D., Department of Chemistry, UMass Lowell
Matthew Gage, Ph.D., Department of Chemistry, UMass Lowell
Carl Lawton, Ph.D., Department of Chemistry, UMass Lowell
Dongming Xie, Ph.D., Department of Chemistry, UMass Lowell

Abstract:
Charge variants, arising from intrinsic post-translational modifications (PTMs) and various degradation pathways, are frequently observed in both recombinant biopharmaceuticals and endogenous proteins. These variants often manifest as shifts in isoelectric point (pI), leading to changes in protein conformation, stability, and functionality. Such alterations can result in reduced potency, adverse immunogenic responses, and modified bioavailability, all of which are directly linked to efficacy and safety — the two determinants for the success of drug development. Therefore, the identification and characterization of charge variants are essential steps in biopharmaceutical analysis.

This study aims to develop comprehensive analytical strategies using two model proteins: a monoclonal antibody (mAb) of the IgG1 class and an Fc-fusion protein, which represent two major categories of biotherapeutics commonly used in clinical practice. An ion exchange-high performance liquid chromatography (IEX-HPLC) method will be developed to fractionate the charge variants, enabling more detailed analysis. A suite of complementary analytical techniques, including size exclusion chromatography (SE-HPLC), SDS-PAGE, glycan profiling, intact mass analysis, and peptide mapping LC-MS, will then be employed to characterize the structural and chemical changes underlying these charge differences. The functional impacts will be evaluated by surface plasmon resonance (SPR), which examines the protein-protein interactions, including stoichiometry, binding kinetics, and binding affinity.

Through these systematic studies, I aim to deepen our understanding of protein charge variants, from their molecular origins to their functional implications. The findings will offer valuable insights for designing biological products with enhanced stability and consistency. Additionally, this research will inform strategies for optimizing production processes, formulation, and storage conditions. The study may also serve as a reference for research on other proteins exhibiting charge variants, especially those associated with pathogenesis and aging-related processes.

All interested students and faculty members are invited to attend.