Starch-iodine complex

Nancy Harrison vulpia at sonic.net
Sun Apr 5 20:45:14 EST 1998


Thanks Jon - this is great information and I can look it up now (never
thought of Salisbury and Ross!). I think the Kakefuda et al paper may
be a bit beyond me but that's a great ref to have. Cheers! -NH


>Nancy and other inquiring minds;
>
>My understanding is that amylose (the nearly unbranched form of starch)
>forms a helix with six glucose units per turn (see Salisbury and Ross,
>Plant Physiology 4th ed. page 247).  Iodine gets into the middle of the
>"tube" and in that environment appears blue or purple.  Amylopectin (the
>branched form of starch) can be purple or red with iodine stain.
>
>You can see an beautiful example of this in a paper by Kakefuda and Duke
>(Plant Physiology 75: 278-280, 1984) in which they ran various starch
>hydrolases on a nondenaturing polyacrylamide gel, then electrophoretically
>transferred the enzymes through a second polyacrylamide gel containing
>starch (like a western transfer).  The enzymes partially chew "holes" in
>the starch as they go and after staining the second gel with iodine the
>holes appear blue, brown, grey or red.  It is a very nice technique but one
>must wear a mask or not talk when setting it up because salivary amylases
>can speckle the second gel with white spots!
>
>Jon
>
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-- 
---Nancy Harrison, SRJC Life Sciences, Santa Rosa CA 95401
   http://www.sonic.net/~vulpia/index.html (with link to CNPS in Sonoma 
County)




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