World Community Grid - View Thread - Using neutron crystallography to study protease inhibitors (HIV)

I thought this was pretty interesting . If you've read about the HIV project you've probably stumbled on the term x-ray crystallography where you create a crystal from the substance you want to study and bounce x-rays off of it.

There are problems with the technique though as seen here. Usually with proteins it's the fact that not all have a rigid, well defined structure and/or are difficult to get to form suitable crystalline structures. Here the problem was a little different so this interesting approach was used. You can read more about it at the wikipedia entry here .

Previously, scientists have studied how protease inhibitors bond to HIV-1 protease through use of X-ray crystallography. X-rays scatter off an atom's electron cloud and so give an indication of an atom's location and what it is bonded to. But protease inhibitors bond to HIV-1 protease largely with hydrogen bonds and since hydrogen atoms have only one electron they are almost invisible to X-rays. According to biochemist Andrey Kovalevsky at Oak Ridge National Laboratory in Tennessee, US, hydrogen bonds can be inferred only from very high-resolution X-ray crystallography, which is difficult to perform on protease inhibitors and enzymes.

Now Kovalevsky, together with Paul Langan at Oak Ridge and colleagues from elsewhere in the US, the UK and France, has tried a more direct approach to study the interactions between protease inhibitors and HIV-1 protease – neutron crystallography. Unlike X-rays, neutrons scatter off atomic nuclei but, more importantly, they scatter just as well off hydrogen as any other type of atom. As a result, neutrons can directly pinpoint the location of hydrogen bonds and how strong they are.