request !

K N and P J Harris ecoli at
Sun Mar 16 08:47:27 EST 1997

As a very simple response
Al can be quite toxic and even possibly mutagenic. Very difficult to 
work with as very sensitive to pH and is a devil in terms of speciation.
Zn is necessary for a number of enzymes hence a little is a good thing, 
lots, on the other hand bring out the "heavy metal" nature of the 
element and it will be toxic in a manner similar to copper or chromium.
Mg is quite interesting. Again an essential element for enzyme activity 
but has other interesting properties. One of them is the apparent 
ability of Mg to protect cells from damage when being transferred from 
very poor nutritional conditions to rich (i.e. average lab media) 

Good luck.
Peter Harris
Reading, U.K.

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