Protein crystallography screening

Currently, this is a major application of protein crystallography in most of the major drug companies. One of the best examples of this approach is the design of inhibitors for HIV protease (Dash et al., 2003). In brief, once the 3-D structure of HIV protease was determined, the active site was identified and used to screen small molecule libraries for potential compounds that could bind to HIV protease. These compounds were then tested for their ability to inhibit the protease. Lead compounds were then used to iteratively improve the inhibitors, using crystallographic studies, computational modeling, and biochemical tests. 

A fully automated protein crystallography beamline at a third-generation synchrotron source can screen several hundred crystals daily. Automatic evaluation of the diffraction images to ascertain crystal quality is, therefore, a critical step for high-throughput data acquisition. Evaluation of each image requires software that mimics the traditional visual assessment of crystal quality. 

The data are at present recorded on video tape for later digitization and processing. The scintillator screen, deposited on a fiber optics face plate is either ZnS(Ag) or Gd S 0(Tb). A spatial resolution of 0,5 mm FWHM has been measured. The system has been used in diffraction measurements of polymer samples and in protein crystallography as well. At present a quantitative analysis of the collected data is in progress. 

In contrast to false positives, false negatives are relatively frequent in protein crystallography, in particular when dealing with low to very low affinity hits from high-throughput screening (HTS) or FBS, for reasons which will... 

Spurlino JC (2011) Fragment screening purely with protein crystallography. Methods Enzymol 493 321-356... 

---