Light scattering, CD, and ligand binding studies of ferrihemoglobin-polyelectrolyte complexes.

Area of Science:

• Biochemistry
• Polymer Science
• Biophysical Chemistry

Background:

• Ferrihemoglobin interactions with charged polymers are crucial for understanding biological systems and developing new biomaterials.
• Polyelectrolytes are widely used in various applications, and their complexation with proteins influences their properties.

Purpose of the Study:

• To investigate the complexation between ferrihemoglobin and three different polyelectrolytes at pH 6.8.
• To determine how variations in polyelectrolyte charge density and sign affect the resulting complex structure and protein binding.

Main Methods:

• Quasi-elastic light scattering (QELS) and electrophoretic light scattering (ELS) were employed to analyze complex size and mobility.
• Circular dichroism (CD) spectroscopy assessed protein structural integrity.
• Azide binding titrations probed changes in ferrihemoglobin's active site upon complexation.

Main Results:

• Complex size and mobility of ferrihemoglobin-poly(diallyldimethylammonium chloride) [PDADMAC] complexes varied with protein concentration, forming intrapolymer complexes at higher protein levels.
• Under excess polyelectrolyte conditions, all ferrihemoglobin molecules were found to be complexed.
• Azide binding was significantly altered with poly(2-acrylamide-2-methylpropanesulfonate) [PAMPS] and showed intermediate changes with a PDADMAC-derived copolymer.

Conclusions:

• Ferrihemoglobin complexation with polyelectrolytes is highly dependent on the polyelectrolyte's charge density and concentration.
• Protein structure remains largely intact during complexation, but the microenvironment around the active site is affected.
• These findings provide insights into protein-polyelectrolyte interactions and their implications for biomaterial design.