I am going to use adult Drosophila to do an ATP assay (ATP determination kit A22066). The most convenient for me is to freeze the samples and perform the experiment later.

However, the protocol provided by the kit producer keeps saying the assay is extremely sensitive, so I'm not sure if it's okay to keep the homogenized samples under -80°C for a short period of time.

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    $\begingroup$ you'll never know for sure unless you run some fresh and run some after freezing - might not be worth the risk $\endgroup$ – Vance L Albaugh Feb 17 '17 at 21:22

Pure ATP can be stable when stored frozen but I would be worried, perhaps unjustifiably, about storing a homogenized sample. You should try dividing a homogenized sample in half and assaying one half right away and the other half after freezing to see how the signals compare.

  • $\begingroup$ Could you elaborate why storing a homogenised sample should be worrying? $\endgroup$ – Arsak Feb 18 '17 at 12:57
  • $\begingroup$ @Marzipanherz I would be worried, perhaps not justifiably, about controlling pH and ATPase activity. $\endgroup$ – canadianer Feb 18 '17 at 19:10
  • $\begingroup$ I was told that there is no (noteworthy) enzyme activity at -80°C. However, I just took this for granted... Guess it's time to find a reliable source for this :) $\endgroup$ – Arsak Feb 18 '17 at 19:20
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    $\begingroup$ @Marzipanherz My supervisor once told me that he was working with a colourimetric substrate that turns from clear to purple during some enzyme-catalyzed reaction. He prepared a stock solution, clear in color, and froze it overnight. The next morning it was purple, presumably due to trace enzyme contamination. There's also the time spent while freezing and thawing it but, again, my concerns may be unfounded. $\endgroup$ – canadianer Feb 18 '17 at 23:10
  • $\begingroup$ That's really interesting! Thank you for sharing! $\endgroup$ – Arsak Feb 19 '17 at 10:03

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