Grant R. Cramer cramer at
Wed Jan 26 12:17:18 EST 2000

Hi Gang,
To clarify my question. We just want to determine if starch remains in our
pellet after digestion with alpha-amylase. Visual assay under the microscope
is that is necessary. If you have any suggestions different from what Jane
Johnson gave me below, please do.

Below is a recipe that I use in an amylase experiment.  I simply add enough
solution to just cover the petri dish, allow it to sit for a few minutes and
remove the KI, it stains starch blue to purple.

Good Luck.

Jane Johnson
UW-Stevens Point

Starch Detection reagent: 0.1% (w/v) I2 /  0.2% (w/v) KI
Makes 2-L.

1. Fill a  2-L glass beaker with about 1600 mL of R.O. water
2. Place a large stir bar in the bottom of beaker
3. Weight out 4.0 g potassium iodide (KI; RT) and transfer crystal to beaker
of water
4. Allow the KI to completely dissolve, do NOT use heat.
5. Weigh out 2.0 g iodine (I2; RT)
6. Add to beaker
7. Allow to spin overnight to completely dissolve (do NOT use heat), but
cover tightly with parafilm
8. Remove stir bar with magnetic wand.
9. Transfer solution to a 2-L graduated cylinder and bring to volume
10. Transfer back to beaker with stir bar and mix for several minutes
11. Dispense 500-mL portion into four midsized-labeled plastic bottles.
12. Store solution at -20oC.  If the solution is not a dark brown color,
check with instructor, fresh may be needed.
Grant R. Cramer
Associate Professor
Mail Stop 200
Department of Biochemistry
University of Nevada
Reno, NV 89557
phone: (775) 784-4204
fax: (775) 784-1650
email: cramer at
web page:


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