For studying glycoproteomics, how much old samples can be used. I have stored samples over the period of 4-5 years. So Can I use these samples for studying glycoproteomics.
Thank you.
if the sample and controls both have been stored at -70, then you can do quantitative glycoproteomics.. I wouldn't be so sure of quantitation at -20 after 5 years.. however if you just plan to identify qualitatively, the glycoproteins or glycopeptides then it could be feasible..
It is well-accepted that colder is usually better, especially when you intend to do discovery (and thus do not know ahead of time what proteins might be of interest). -70 to -80 would be good, LN2 even better. I agree that -20 may not be very good.
Also, frost-free storage is usually bad for proteins -- so if your freezer has a self-defrost capability, your samples likely will be in very poor condition. Some -20 freezers actually are frost-free (and bad for us!).
For future reference, one of the original HUPO articles (see my publications) described the basics: freeze low, freeze soon after collection, avoid freeze-thaw as much as possible.
If you have not done so yet, when you thaw each sample, aliquot it into the smallest possible volumes for single use (maybe 50 microliters or less) and freeze those aliquots. That way, you only thaw exactly what you will use for one experiment, and the rest of the sample stays as safe as possible in the freezer.
The above comments are good, informative, and supportive, but you'll have to be VERY skeptical of any results you get from samples that are that old!
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