Ligand-Binding Cooperativity Effects in Polymer-Protein Conjugation.

Area of Science:

• Biomaterials Science
• Spectroscopy
• Polymer Chemistry

Background:

• Bovine serum albumin (BSA) is a model protein for polymer-protein conjugation, relevant for drug delivery and biocompatibility.
• Post-translational modifications (PTMs) can alter protein structure and function, impacting biological interactions.
• Understanding these modifications is crucial for designing advanced biomaterials.

Purpose of the Study:

• To characterize structural and dynamic effects of PTMs on BSA using EPR spectroscopy.
• To investigate how polymer conjugation influences BSA's internal dynamics and ligand-binding properties.
• To quantify the impact of surface modification extent on BSA's functionality.

Main Methods:

• Electron paramagnetic resonance (EPR) spectroscopy to study ligand uptake and binding dynamics.
• Dynamic light scattering (DLS) and zeta potential measurements for characterizing conjugates.
• Double electron electron resonance (DEER) experiments to analyze ligand spatial alignment.

Main Results:

• Ligand-binding affinity, cooperativity, and site number in BSA change drastically with surface modification extent.
• Protein-attached polymers act as diffusion barriers, hindering ligand uptake.
• Zeta potential decreases linearly with surface modification, and an effective dielectric constant for the polymer layer can be estimated.

Conclusions:

• PTMs and polymer conjugation significantly fine-tune BSA's ligand uptake characteristics.
• EPR spectroscopy is a suitable method for quantifying PTM-based functional effects in self-assembled systems.
• The study provides insights into designing functional polymer-protein conjugates by controlling modification extent.