Energetics and Mechanism of Conformational Transitions of Protein-Like NIPAM-Sodium Styrene Sulfonate Copolymers in Aqueous Solutions

Protein‐like and random NIPAM‐sodium styrene sulfonate copolymers of similar composition have been prepared by radical polymerization in water at temperatures above and below the LCST of PNIPAM, respectively. Thermal transitions of the copolymers in aqueous solutions have been studied by means of dy...

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Bibliographic Details
Published in:	Macromolecular chemistry and physics Vol. 216; no. 24; pp. 2344 - 2355
Main Authors:	Grinberg, Valerij Y., Burova, Tatiana V., Grinberg, Natalia V., Dubovik, Alexander S., Plaschina, Irina G., Laptinskaya, Tatiana V., Xiong, Yubing, Yao, Ping, Khokhlov, Alexei R.
Format:	Journal Article
Language:	English
Published:	Weinheim Blackwell Publishing Ltd 01-12-2015 Wiley Subscription Services, Inc
Subjects:	accessible solvent area Aqueous solutions coil-globule transitions Coiling Copolymers globule structure Globules Mathematical models Phase separation Protein folding protein-like copolymers Specific heat Styrenes Sulfonates thermodynamics
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Summary:	Protein‐like and random NIPAM‐sodium styrene sulfonate copolymers of similar composition have been prepared by radical polymerization in water at temperatures above and below the LCST of PNIPAM, respectively. Thermal transitions of the copolymers in aqueous solutions have been studied by means of dynamic light scattering, viscometry, and high‐sensitivity differential scanning calorimetry. The phase separation or cooperative conformational transitions without phase separation were observed for the random or the protein‐like copolymers, respectively. Transition temperature, enthalpy, and heat capacity increment of the protein‐like copolymer differed insignificantly from those of the random copolymer of similar composition. The transition heat capacity increments of the protein‐like copolymers revealed that only 10–20% of their NIPAM links participate in the formation of a dense water‐free globule core. The coil–globule transitions of the protein‐like copolymers were described by the thermodynamic three‐state model according to the scheme “random coil↔condensed coil↔globule”, which is known to simulate the folding mechanism of globular proteins. Mechanism of conformational transitions of the protein‐like copolymers and structure of their compact states are governed by a balance of electrostatic and hydrophobic interactions. The protein‐like copolymers undergo the coil–globule transition under salt‐free conditions, the conjugated consecutive transitions “coil↔globule↔cluster of globules” in the presence of salt, and the “coil↔necklace‐like chain” transition at a concentration of SDS above its CAC.
Bibliography:	ark:/67375/WNG-6J67LT89-X ArticleID:MACP201500253 istex:E6D8BB486A021DFC411988961ED298258D334B4F Russian Science Foundation - No. 14-13-00544 ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	1022-1352 1521-3935
DOI:	10.1002/macp.201500253