Since I was talking about peptide synthesis yesterday, and the usefulness of peptides in general, I thought a few back-of-the-envelope calculations would be interesting. After all, if we're going to be making the things, we should know what we're getting into.
How about a combichem library of the things? Let's see. . .since someone mentioned vasopressin and oxytocin, let's figure that other 9-mers could have some interesting activity. What if we want them all? With the twenty most common amino acids in hand, and our peptide synthesizer machines recently serviced and reloaded, we throw the switch and. . .a mere five hundred and twelve billion peptides later, our library is ready for screening.
Ahem. That's well more than ten thousand times the number of organic substances that are indexed in Chemical Abstracts. This exponential stuff gets out of hand pretty quickly. Storing the stuff will be a problem. At, say, ten milligrams per compound, we're looking at five million kilos of peptides, and that's before the glass vials are added in. Protein folks look aghast if you talk about producing as much as ten milligrams of any given peptide, but hey, if we're going to turn the things into drugs, we have to get ready to work on scale.
And if we're going to make drugs, we're probably going to have to deal with some unnatural amino acids to improve metabolic stability. That has an effect, too, as you'd figure. Adding in one extra gives you an extra two hundred and seventy billion peptides, which is certainly value for your synthesis dollar. If you're going to get the deluxe package, with the D and L forms of the nineteen chiral ones, that'll run your screening file up to 200 trillion total, which is going to put a real strain on the chemical synthesis capacity of the entire world economy. Call ahead.
So a library of 26-mers, the size of Fuzeon, is going to be really hard to handle. That comes to a cool 6.71 times ten to the thirty-third power, which is beginning to get into the realm of really substantial numbers. At ten mgs per compound, we're down to the 6.7 times ten to the 25th metric tons, which is only a bit more than. . .ten thousand Earths. Well, ten thousand Earths made up of an even mixture of the twenty amino acids, that is, rather than boring old inorganic rock.
Let's just say that there's a lot of patent space, and plenty of reduction-to-practice loopholes, and leave it at that. . .