Fluorescein casein

Fig. 3 - Displacement of the fluorescent probe fluorescein hydrozino methylene imazepyr (FHMI) by imazethapyr. The Ab-coated fiber was perfused with the flow buffer (PBS/casein, 25 nM FHMI until fluorescence reached a steady state (<10 min). The FHMI was removed and the fiber was perfused with PBS/casein containing imazethapyr for 2 min then the flow buffer was reintroduced. Fluorescence recovered back to the steady state level. This process was repeated 5 more times using increasing concentrations of imazethapyr. In other words a single fiber was used to generate all the data. Reproduced with permission from reference 2, Copyright 1993 American Chemical Society.

The levels of several infra- and extracellular enzyme activities are also determined. Whole-ceU proteolytic activity is determined by measuring fluorescence development after exposure to fluorescein isothiocyanate (FITC) - tagged casein (Twining, 1984). This proteolytic activity is important for acidification of milk and flavor development (H0ier et al., 2010). Intracellular enzyme activities are measured following cell lysis by sonicalion using a custom-made 96-pin sonication head (Misonix Inc.,... 

Twining, S. (1984). Fluorescein isothiocyanate-labeled casein assay for proteolytic enzymes. Analytical Biochemistry, 143, 30-34. 

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