Hello!
I am working on investigating the effect of freeze and thaw on the peptides stability. The peptide is relatively short less than 50 AA so my question is would this have an impact at all? Is it work exploring this? Does controlled freeze thaw a valid solution?
The covalent bonds in the peptide will not be harmed by freeze-thaw. If the peptide has tertiary structure, there is a possibility that it could be damaged by freeze thaw. My guess is that the only significant risk is aggregation, if the peptide has a tendency to do that. To minimize the risk, divide the peptide solution into small aliquots so that no single aliquot has to be used more than a few times. Always flash-freeze the solution by placing it in liquid nitrogen, a dry ice-ethanol bath, or powdered dry ice.
In general, yes, freeze-thaw cycles can indeed have an effect on the stability of peptides. Peptides are generally sensitive molecules and can be susceptible to degradation or structural changes under certain conditions, including temperature fluctuations.
If you have a pH sensitive peptide / protein then check your buffer!
When you freeze essentially "everything" (an oversimplification) then jumps out of solutions. You can visualise this by freezing buffer and adding some universal indicator solution and freezing the samples. The pH indicated by the colour of the solution can change quite dramatically when frozen. Some buffer salts are more prone to pH shift when freezing - from memory phosphate buffer is a bad one, but do check!
I have also heard that the pH of phosphate buffer changes when freezing, so it is not preferred for a storage solution with sensitive materials.
If the solution is flash-frozen, the solutes do not have time to separate from the ice, so this method is preferable to slow-freezing.
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