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Role of Carboxylate Side Chains in the Cation Hofmeister Series.
MedLine Citation:
PMID:  22697172     Owner:  NLM     Status:  Publisher    
Thermodynamic and surface-specific spectroscopic investigations were carried with an elastin-like polypeptide (ELP) containing 16 aspartic acid residues. The goal was to explore the role of the carboxylate moieties in hydrophobic collapse and related Hofmeister effects. Experiments were conducted with a series of monovalent and divalent metal chloride salts. Both phase transition temperature and spectroscopic data demonstrated that the divalent cations showed relatively strong association to the carboxylate sites on the biopolymer with K(d) values in the range of 1 to 10 mM. The ordering of the divalent series was: Zn(2+) > Ca(2+) > Ba(2+) > Sr(2+) > Mg(2+). Monovalent cations displayed weaker binding which ranged from 78 mM for NH(4)(+) to 345 mM for Cs(+). The order for this series was: NH(4)(+) > Li(+) > Na(+) > NMe(4)(+) > K(+) > Rb(+) ≥ Cs(+). These results are in general agreement with the notion that strongly hydrated cations bind more tightly to carboxylate groups than do weakly hydrated cations. Moreover, the data for the monovalent series was partially consistent with the law of matching water affinity, although Li(+) and NH(4)(+) did not follow the model. The series for the divalent cations did not appear to obey the law of matching water affinity at all.
Jaibir Kherb; Sarah C Flores; Paul S Cremer
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-6-14
Journal Detail:
Title:  The journal of physical chemistry. B     Volume:  -     ISSN:  1520-5207     ISO Abbreviation:  -     Publication Date:  2012 Jun 
Date Detail:
Created Date:  2012-6-15     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101157530     Medline TA:  J Phys Chem B     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Department of Chemistry, Texas A & M University , College Station, Texas 77843, United States.
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