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Lidstrom:Buffers: Difference between revisions
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→How do method developer chose between sodium and potassium phospahte buffers?
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*** Sometimes Na precipitates when K wouldn't & vice versa | *** Sometimes Na precipitates when K wouldn't & vice versa | ||
* Michael Konopka's words: "What assays are you trying to measure? As for the buffering capacity, that really shouldn't matter since the pertinent components for the buffer (mono- and di-basic phosphate) are the same. The issue is if the potassium or sodium ion will form a precipitate which you don't want around if mixing with other solutions (or do want). A classic example is potassium will precipitate SDS while sodium is soluble. That's why in minipreps one adds potassium acetate/acetic acid after using SDS/NaOH to lyse the cells/dissolve lipids & proteins. The proteins, lipids, and chromosomal DNA is then trapped in the precipitate (plasmid DNA still in solution)." | * Michael Konopka's words: "What assays are you trying to measure? As for the buffering capacity, that really shouldn't matter since the pertinent components for the buffer (mono- and di-basic phosphate) are the same. The issue is if the potassium or sodium ion will form a precipitate which you don't want around if mixing with other solutions (or do want). A classic example is potassium will precipitate SDS while sodium is soluble. That's why in minipreps one adds potassium acetate/acetic acid after using SDS/NaOH to lyse the cells/dissolve lipids & proteins. The proteins, lipids, and chromosomal DNA is then trapped in the precipitate (plasmid DNA still in solution)." | ||
=== Why are some buffers degassed during preparation? === | |||
* CO<sub>2</sub> forms carbonic acid in water, and can affect pH. It can, however, be removed from the water before buffer is prepared. | |||
== Notes specific to buffers == | == Notes specific to buffers == | ||
