What is the most relevant website to predict the thermostability of peptides?
I don't think you need a website! If it has no disulphide bonds it is thermostable, at least to boiling. Disulphide bonds are disrupted by boiling. So for example, insulin activity is completely lost on boiling; whereas glucagon (just a straight chain peptide) is thermostable.
I will try to clarify for you. For short peptides, the situation is easy. No disulphide bonds (as in glucagon) = thermostable (you can boil and not lose structure or activity). In the case of a single disulphide bond (as in somatostatin) you can still boil and retain structure and activity because the peptide will spontaneously reform on cooling - producing the cyclic peptide again. In the case of insulin, with two chains and multiple disulphide bonds, the chances of the correct configuration occurring after boiling and cooling are extremely low and so recovery of intact, biologically active insulin after boiling is extremely low. Banting and Best discovered this, since boiling would clearly destroy the proteolytic acitivity of their pancreatic extracts, but it unfortunately also destroyed the insulin activity. Thus they developed the acid/ethanol extraction method for extraction of active insulin, that was employed for many decades in the commercial production of insulin from animal pancreati (before the development of recombinant insulin from bacteria).
In the case of proteins with multiple disulphide bonds, of course they are all destroyed by boiling, but will show subtle differences in the degree of thermostability at lower temperatures (depending on the resistance of the individual disulphide bonds to temperature change.. These subtle differences can be altered by mutations or changes in the protein structure.
Hope this helps.
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