I am currently using NH4OH to elute a protein from a bead-antibody complex in order to analyze it by mass spectrometry. Compared to previous assays we obtained fragmentation of the protein, so I was wondering if this degradation could come from the method of storage. As the freezing point of NH4OH is -91.5°C and liquid nitrogen is at -80°C, is the protein well-conserved at -80°C if diluted in NH4OH ? Or does it affect the integrity of the protein ?
Hello Perrine,
When the sample is frozen, there can be a pH shift. The salt and proten come out of solution when freezing, they are no-longer dissolved. [If you want to do a nice visual test, take your salt solution, add universal indicator solution and freeze a tube - compare to unfrozen sample.] Depending on the pH stability of the protein, the pH shift can cause a problem.
Kind regards,
Rob
Rob Darrington Thank you very much for your advice, I will try to test your hypothesis.
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