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Lidstrom:Buffers: Difference between revisions
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* 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)." | ||
== Notes == | == Notes specific to buffers == | ||
=== phosphate buffer === | |||
* Phosphates, for example, form insoluble salts with bivalent metals and precipitate. Phosphate buffered salt solution (PBS) is never | |||
autoclaved with Ca2+ or Mg2+ for this reason. Good buffers, such as PIPES, TES, HEPES and CAPS have very low metal-binding | |||
constants and are therefore particularly suited to investigate metal-dependent enzymes (Good & Izawa 1972, Blanchard | |||
1984). [http://www.applichem.com/fileadmin/Broschueren/BioBuffer.pdf Applichem] | |||
