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Effect of amides and ureas on the reversible gelation of arachin

Navin Kumar, D. Kella (1987) Effect of amides and ureas on the reversible gelation of arachin. International Journal of Biological Macromolecules, 9 (4). pp. 238-244.

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The effect of formamide and urea and their amino-substituted derivatives dimethyl formamide and tetramethyl urea (at 1 m level) on thermal denaturation and protein protein interactions (at pH 3.6) that led to gelation of arachin were studied by gel melting temperature, electrophoresis, u.v. difference and fluorescence spectral measurements. Melting temperature and electrophoretic measurements showed that formamide and urea decreased the heat-induced protein-protein interactions while their methyl derivatives had the opposite effect. Melting temperature measurements also revealed a decrease in both -ΔHbonding and -ΔSbonding in the presence of formamide and urea while their methyl derivatives increased these thermodynamic parameters. In both the cases urea and tetramethyl urea had a greater effect on changing both the thermodynamic parameters compared with formamide and dimethyl formamide respectively. U.v. difference and fluorescence spectral measurements suggested that addition of formamide, urea and their methyl derivatives at 1 m level to orachin at pH 3.6 and room temperature induced unfolding. Addition of these compounds to the heated arachin solution at the same pH also promoted the thermal denaturation of the protein. The effectiveness followed the order tetramethyl urea > urea > dimethyl formamide > formamide. The promotive effect of formamide and urea on thermal denaturation and their preventive effect on the protein-protein interactions of arachin could be due to their favourable interaction with interpeptide hydrogen bonds. On the other hand, the promotive effect of dimethyl formamide and tetramethyl urea on the thermal denaturation of the protein may be due to their solubilization effect on the intraprotein hydrophobic interactions. The increase in protein-protein interactions in the presence of these compounds could be due to an increase in interprotein hydrogen bonding. This hypothesis of the mechanism of the additives on the heat-induced protein-protein interactions at pH 3.6 is consistent with the measured thermodynamic parameters of gelation.

Item Type: Article
Uncontrolled Keywords: Arachin; gelation; thermal denaturation; protein-protein interactions; protein-amide interactions
Subjects: 500 Natural Sciences and Mathematics > 04 Chemistry and Allied Sciences > 29 Protein Chemistry
Divisions: Protein Chemistry and Technology
Depositing User: Food Sci. & Technol. Information Services
Date Deposited: 07 Jun 2012 11:08
Last Modified: 22 Feb 2018 10:39
URI: http://ir.cftri.com/id/eprint/10821

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