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Many molecular biology recipes use MgSO4 (and not MgCl2). Is there indeed a preference? If so, why?

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closed as unclear what you're asking by GriffinEvo, fileunderwater, Satwik Pasani, Chris, WYSIWYG Feb 19 at 10:55

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Can you specify which recipes you mean? I am aware of a number of polymerases like Pfu which prefer $ MgSO_4 $. I haven't found a reference for that now, but its probably the same: The chloride ion interferes with the enzymes reaction. –  Chris Feb 18 at 17:38
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1 Answer 1

My guess is its the solubility properties of the anions.

Chloride ions can precipitate with some metals that might appear in a complicated buffer or medium. And yes they could even compete with enzyme binding. Sulfate will remain in solution with just about anything.

There are exceptions, but if you're making a buffer you're probably going to do better if you use the general solubility rules.

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Are you sure about the insoluble chloride salts? I recall only a handfull of them, mostly with ions, which are not common in cells like titanium or silver. For sulphate I agree completely. –  Chris Feb 18 at 18:31
    
Although calcium sulphate is only sparingly soluble. –  Alan Boyd Feb 18 at 20:44
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added a link... this is chem 101 so nearly every book has a mention of some form of counter-ion solubility rules. –  shigeta Feb 18 at 23:21
    
@AlanBoyd A number of sulphates is nearly insoluble. –  Chris Feb 19 at 6:42
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@shigeta Thats a good link, thanks for it. –  Chris Feb 19 at 8:40
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