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Biomacromolecules. 2010 Nov 8;11(11):2873-9. doi: 10.1021/bm100571j. Epub 2010 Oct 6.

Quantitative model of the phase behavior of recombinant pH-responsive elastin-like polypeptides.

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1
Department of Biomedical Engineering, Duke University, 101 Science Drive, Durham, North Carolina 27708-0281, United States, St. Jude Medical, 11175 Cicero Drive, Suite 675, Alpharetta, Georgia 30022, United States, and Department of Pharmacology and Pharmaceutical Sciences, University of Southern California, 1985 Zonal Avenue, Los Angeles, California 90033-9121, United States.

Abstract

Quantitative models are required to engineer biomaterials with environmentally responsive properties. With this goal in mind, we developed a model that describes the pH-dependent phase behavior of a class of stimulus responsive elastin-like polypeptides (ELPs) that undergo reversible phase separation in response to their solution environment. Under isothermal conditions, charged ELPs can undergo phase separation when their charge is neutralized. Optimization of this behavior has been challenging because the pH at which they phase separate, pHt, depends on their composition, molecular weight, concentration, and temperature. To address this problem, we developed a quantitative model to describe the phase behavior of charged ELPs that uses the Henderson-Hasselbalch relationship to describe the effect of side-chain ionization on the phase-transition temperature of an ELP. The model was validated with pH-responsive ELPs that contained either acidic (Glu) or basic (His) residues. The phase separation of both ELPs fit this model across a range of pH. These results have important implications for applications of pH-responsive ELPs because they provide a quantitative model for the rational design of pH-responsive polypeptides whose transition can be triggered at a specified pH.

PMID:
20925333
PMCID:
PMC3032028
DOI:
10.1021/bm100571j
[Indexed for MEDLINE]
Free PMC Article
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