Interaction of Cetyltrimethylammonium Bromide and Its Gemini Homologue Bis(cetyldimethylammonium)butane Dibromide with Xanthine Oxidase

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• 作者：Mohammad Amin Mir ; Javed Masood Khan ; Rizwan Hasan Khan ; Aijaz Ahmad Dar ; Ghulam Mohammad Rather
• 刊名：The Journal of Physical Chemistry B
• 出版年：2012
• 出版时间：May 17, 2012
• 年：2012
• 卷：116
• 期：19
• 页码：5711-5718
• 全文大小：387K
• 年卷期：v.116,no.19(May 17, 2012)
• ISSN：1520-5207

文摘

The interaction of xanthine oxidase (XO), a key enzyme in purine metabolism, with cetyltrimethylammonium bromide (CTAB) and bis(cetyldimethylammonium)butane dibromide (C₁₆C₄C₁₆Br₂) has been studied using tensiometry, spectrofluorometry, spectrophotometry, and circular dichroism at pH 7.4 and 25 掳C. The tensiometric profiles of CTAB and C₁₆C₄C₁₆Br₂ in the presence of XO exhibit a single break at a lower surfactant concentration termed as C₁ compared to their CMC in the buffered solution and show the existence of interaction between the surfactants and the enzyme. The results of the multitechnique approach showed that, although both CTAB as well as C₁₆C₄C₁₆Br₂ interact with the XO, C₁₆C₄C₁₆Br₂ interacts more strongly than its conventional single chain counterpart. Fluorescence and absorption measurements revealed that, compared to CTAB, C₁₆C₄C₁₆Br₂ is more effective in unfolding the enzyme. Change in XO activity by the surfactants was in concurrence with the structural alterations monitored by circular dichroism and showed structural stabilization of XO at higher surfactant concentrations, consistent with the aggregation results. This stabilization has been explained in light of strong tendency of C₁₆C₄C₁₆Br₂ for micellar growth and membrane/water stabilization of proteins by membrane-like fragments provided by higher concentrations of C₁₆C₄C₁₆Br₂ . The results are related to the stronger electrostatic and hydrophobic forces in C₁₆C₄C₁₆Br₂, owing to the presence of two charged headgroups and two hydrophobic tails.