When a malaria parasite lands in your blood, one of the first things it does is whip out its scissors. As fast as it can, this protozoan snips the hemoglobin in red blood cells to get the nutrients it needs to survive. Of course, the microbe behind this deadly disease doesn’t actually deploy stainless-steel blades. Instead, it uses an array of biochemical scissors known as proteases.

Proteases are enzymes that snip proteins. They recognize certain strings of amino acids on a substrate protein, bind to this area, then break a nearby chemical bond. Proteases can destroy proteins by snipping them in half, as in malaria. They can also activate proteins by lopping off atoms covering a reactive site.

This versatility has made proteases critical to all manner of organisms, from viruses to plants to humans. Over the past 10 years, protease inhibitor drugs have become indispensable in the fight against AIDS, cardiovascular disease and diabetes. But finding protease inhibitors is no picnic. Humans manufacture tens of thousands of proteins; figuring out which of these a protease targets is extremely challenging and time consuming.
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Instead of mixing liquid chemicals and painstakingly purifying them again at each step, he attaches his precursor molecules to polystyrene beads resembling sand grains.