Issue 29, 2015

Ion specificity of macromolecules in crowded environments

Abstract

Macromolecular crowding plays a significant role in the solubility and stability of biomacromolecules. In this work, the thermo-sensitive poly(N-isopropylacrylamide) (PNIPAM) has been employed as a model system to study the specific ion effects on the solubility of macromolecules in crowded environments of dextran and polyethylene glycol (PEG). Our study demonstrates that crowding agents can interact with either anions or PNIPAM chains. The chaotropic anion SCN interacts with dextran but does not interact with PEG. Both Cl and CH3COO do not interact with dextran and PEG. On the other hand, dextran can interact with PNIPAM as a hydrogen-bond donor, whereas PEG interacts with PNIPAM as a hydrogen-bond acceptor. The salting-in effect exerted by SCN on PNIPAM is weakened in the crowded environment of dextran but is strengthened in the crowded environment of PEG due to the distinct anion-crowder interactions. In parallel, the salting-out effect generated by Cl and CH3COO on PNIPAM is weakened by the crowding of dextran but is strengthened by the crowding of PEG because of the different macromolecule–crowder interactions. Our study reveals that the ion specificity of macromolecules is altered significantly changing from dilute solutions to crowded environments.

Graphical abstract: Ion specificity of macromolecules in crowded environments

Supplementary files

Article information

Article type
Paper
Submitted
29 Apr 2015
Accepted
10 Jun 2015
First published
10 Jun 2015

Soft Matter, 2015,11, 5940-5946

Ion specificity of macromolecules in crowded environments

W. Song, L. Liu and G. Liu, Soft Matter, 2015, 11, 5940 DOI: 10.1039/C5SM01023C

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