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Charge reversal by salt-induced aggregation in aqueous lactoferrin solutions
Ioanna Mela1, Elodie Aumaitre, Ann-Marie Williamson
1Unilever Discover, Colworth Science Park, Sharnbrook, Bedford, UK.
Colloids and Surfaces. B, Biointerfaces
|March 9, 2010
Summary
Salt increases the ionic strength in lactoferrin solutions, causing protein aggregation. These negatively charged lactoferrin aggregates bind only to positively charged surfaces, influencing protein adsorption behavior.
Area of Science:
- Biochemistry
- Materials Science
- Surface Chemistry
Background:
- Lactoferrin is an iron-binding glycoprotein with diverse biological functions.
- Protein aggregation can alter biological activity and material properties.
- Understanding salt-induced aggregation is crucial for controlling protein behavior in solution and at interfaces.
Purpose of the Study:
- To investigate the phenomenon of salt-induced aggregation in lactoferrin solutions.
- To characterize the properties of these aggregates, including their charge and size.
- To examine the adsorption behavior of lactoferrin and its aggregates on surfaces with different charges.
Main Methods:
- Dynamic Light Scattering (DLS) to detect and size aggregates.
- Electrophoretic measurements to determine aggregate charge and isoelectric point.
- Atomic Force Microscopy (AFM) to image adsorbed lactoferrin films on various surfaces.
Main Results:
- Salt-induced aggregation of lactoferrin begins above 10 mM ionic strength.
- Aggregates possess a charge opposite to that of lactoferrin monomers.
- Negatively charged lactoferrin aggregates adsorb exclusively onto positively charged surfaces.
- Lactoferrin monomers adsorb to both positive and negative surfaces without charge inversion.
Conclusions:
- Lactoferrin aggregation is salt-dependent and results in oppositely charged species.
- Surface charge dictates the adsorption of lactoferrin aggregates, not individual molecules.
- The amphiphilic nature of lactoferrin allows monomer adsorption on diverse surfaces.
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