The reason SHA256 was chosen is that it is a hash function. Hash functions are meant to be easy to calculate but difficult or near impossible to reverse and near impossible to optimize.

MD2 was designed by cryptographers and has tons of research regarding it's security. It is now broken.

Protein folding basically has no research regarding it's security as a hash function, because it isn't designed as a hash function.

Protein folding almost certainly has a large optimization problem, an attacker likely could find ways to increase his mining power by orders of magnitude. If the currency became valueable, it is inevitable that someone would make solving this problem constant time.

Now, is making protein folding more a efficient a good thing? Absolutely! But the only way it can be made more efficient is by making this currency useless.

Essentially, the only way this currency can be useful to DNA folding is if the currency becomes useless for securing money.

Edit: It appears that foldingcoin is on top of the bitcoin blockchain so miners aren't even there for consensus. They are simply creating a speculative asset that has an increasing monetary supply that equates to donations to protein folding. The miners are completely unnecessary for security.