Surface patch binding and mesophase separation in biopolymeric polyelectrolyte–polyampholyte solutions

Surface patch binding (SPB) induced mesophase separation causing complex coacervation between biopolymers: gelatin A–gelatin B, chitosan–gelatin A, chitosan–gelatin B, and, agar–gelatin B was investigated with and without salt (I=0–0.3M NaCl). SPB was induced by pH change and three characteristic pH...

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Bibliographic Details
Published in:International journal of biological macromolecules 2014-02, Vol.63, p.29-37
Main Authors: Pathak, Jyotsana, Rawat, Kamla, Bohidar, H.B.
Format: Article
Language:English
Subjects:
Agar - chemistry
Biopolymers - chemistry
Chitosan - chemistry
Complex coacervation
Electrolytes
Gelatin - chemistry
Hydrogen-Ion Concentration
Interaction potential
Osmolar Concentration
Phase diagram
Protein Binding
Sodium Chloride - chemistry
Solutions - chemistry
Static Electricity
Surface patch binding
Surface Properties
Temperature
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Summary:Surface patch binding (SPB) induced mesophase separation causing complex coacervation between biopolymers: gelatin A–gelatin B, chitosan–gelatin A, chitosan–gelatin B, and, agar–gelatin B was investigated with and without salt (I=0–0.3M NaCl). SPB was induced by pH change and three characteristic pHs identified transitions in a turbidity plot: intermolecular interactions ensued at pHc, coacervation transition occurred at pHΦ and phase separation was noticed at pHprep. Associative interactions lead to formation of soluble complexes at pHc exclusively through SPB whereas the coacervation transition was driven by electrostatic binding (EB). Neither pHc nor pHΦ displayed discernible ionic strength (till 50mM) or temperature dependence, but coacervate yield reduced with increase in ionic strength. Coacervation was completely suppressed beyond 50mM NaCl. Linear combination of attractive and repulsive parts operating between a polyelectrolyte (charged rod) with a polyampholyte (dipole or point charge) was used to model the interaction potential as function of ionic strength. Relative strength of SPB vis a vis EB was used as SPB index to establish a linear relationship with zeta potential ratio of binding partners. Different phase diagrams could be constructed which clearly identified distinct interaction regimes encountered in solutions undergoing coacervation transition.
ISSN:0141-8130
1879-0003
DOI:10.1016/j.ijbiomac.2013.10.020