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Characterization of chymotrypsin-ι-carrageenan complex in aqueous solution: a solubility and thermodynamical
Nadia Woitovich Valetti1, Valeria Boeris, Guillermo Picó
1Laboratory of Physical Chemistry Applied to the Bioseparation, Faculty of Biochemical and Pharmaceutical Sciences, CONICET, National University of Rosario, Suipacha 570, S2002RLK Rosario, Argentina.
Abstract:
The aim of this study is to report the results of research work on the molecular mechanism of complex formation between chymotrypsin and a negatively charged natural strong polyelectrolyte, ι-carrageenan, using spectroscopy techniques. The carrageenan-chymotrypsin complex showed a maximal non-solubility at pH around 4.50 with a stoichiometric ratio between 8 and 33 g of chymotrypsin per g of carrageenan. These values were depended on the enzyme concentration, pH and ionic strength medium. The insoluble complex was redissolved by modifying the pH and by a NaCl concentration around 0.2 M in agreement with a coulombic mechanism of complex formation. The non-soluble complex formation showed biphasic kinetics. A fast step was carried out around 10 s and a coulombic mechanism takes place, and a slower step of around 120 s, where participate only Van der Waals forces. The enzymatic activity of chymotrypsin was maintained even in the presence of carrageenan (0.005%, w/v).
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