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Insight into the effect mechanism of urea-induced protein denaturation by dielectric spectroscopy

Abstract

Dielectric relaxation spectroscopy was applied to study how urea affects the phase transition of thermosensitive polymer——poly (N-isopropylacrylamide) (PNIPAM) which has been widely used as the protein model. It was found that there is a pronounced relaxation near 10GHz for the ternary system of PNIPAM in urea aqueous solution. The temperature dependence of dielectric parameters indicates that urea can reduce the lower critical solution temperature (LCST) of PNIPAM, i.e., stabilize the globule state of PNIPAM and collapse the PNIPAM chains. Based on our results, the interaction mechanism of urea on the conformational transition of PNIPAM was presented: urea replaces water molecules directly bonding with PNIPAM and acts as the bridging agent for the adjacent side chains of PNIPAM. Accordingly, the mechanism that urea denatures protein was deduced. In addition, it is worth mentioning that, from the temperature dependence of the dielectric parameters obtained in the presence of urea, an interesting phenomenon was found that the effect of urea on PNIPAM seems to take 2M as a unit. This result may be the reason why urea and TMAO exit in marine fishes at a specific ratio of 2:1.

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Publication details

The article was received on 02 Sep 2017, accepted on 06 Nov 2017 and first published on 06 Nov 2017


Article type: Paper
DOI: 10.1039/C7CP05994A
Citation: Phys. Chem. Chem. Phys., 2017, Accepted Manuscript
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    Insight into the effect mechanism of urea-induced protein denaturation by dielectric spectroscopy

    C. Zhang, M. Yang and K. Zhao, Phys. Chem. Chem. Phys., 2017, Accepted Manuscript , DOI: 10.1039/C7CP05994A

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