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<html> <head> <title></title> </head> <body> <p><strong>Urease Activity Assay.</strong></p>

<p>A <strong>colorimetric assay</strong> based on the<br /> hydrolysis of urea was used for the activity control of free and<br /> immobilized urease, as monitored by the pH-sensitive dye<br /> bromcresol purple. The enzymatic reaction was monitored by<br /> following the dye absorption at 588 nm.18,19 A control solution<br /> containing 25 mM urea, 0.015 mM bromcresol purple, and 0.2<br /> mM EDTA was adjusted to pH 5.8. This solution was placed in a<br /> 3-mL UV cell and magnetically stirred. A known amount of the<br /> urease multilayer-coated PS spheres (or free urease for the<br /> calibration) was then added, and the kinetics were monitored by<br /> following the absorption at 588 nm. The solution changed from<br /> yellow to dark purple during the reaction, corresponding to a<br /> change in solution pH from 5.8 to 7.5. The increment of the<br /> absorbance with time was used to characterize the urease activity<br /> in the sample</p> </body> </html>

<html> <head> <title></title> </head> <body> <p><strong>Blibliografia&nbsp;</strong></p>


<p>Biocolloids with Ordered Urease Multilayer Shells<br /> as Enzymatic Reactors<br /> Yuri Lvov&dagger; and Frank Caruso*,&Dagger;<br /> Institute for Micromanufacturing, Louisiana Tech University, Ruston, Louisiana 71272, and Max Planck Institute of Colloids<br /> and Interfaces, D-14424 Potsdam, Germany</p> </body> </html>