In reference to the patent: US5933819
I think this is not patentable, but does need protection.
Without knowing the details, applying a neural network algorithm to a problem is not even an idea, it is common course of the art. IF, authors made some modification to the NNA, it may deserve patenting, but not if any researcher in the same area will find the same modification - because it is obviously needed to adapt the algorithm to the problem.
I think this case should be treated like a Trade Secret if applied commercially, otherwise should be considered general research and made public.
I found the patent by simply searching for peptide NN. Does this mean I should not even TRY to apply the algorithm to the problem but instead should start paying rights to these authors if I use it commercially?
Cases like this one deserve a PRIZE in lieu of rights, but not a restrictive patent.