Fluorimetric measurement of the activity of surface-immobilized monolayers of enzyme using a dual emission probe

A sensitive assay for measurement of the activity of hydrolase enzymes that are immobilized onto quartz and silicon dioxide surfaces was developed. Measurements are based on the changes of the fluorescence properties of the probe carboxy-seminaptharhodafluor-X that are caused by pH variations associated with the reaction of urea with urease. The results indicated a loss of activity in 8 days, and a half-life of 3 days, when urease was immobilized onto quartz surfaces that were first derivatized with a 16-carbon spacer chain.