Creative Biostructure provides a complete contract crystallography service to support coronavirus infection-related research, including gene-to-structure pipelines at all stages from protein expression to structure determination. After successfully obtaining the high-quality diffraction pattern and diffraction data, the next challenge is to obtain the electron density map, which is the basis for reconstructing three-dimensional (3D) structural models and deducing detailed structural information. We can perform data processing and analysis based on high-resolution X-ray diffraction data to determine and refine the crystal structure.
Since December 2019, coronavirus disease 2019 (COVID-19) has erupted and rapidly spread across the world, and the number of infections and deaths continues to increase. Up to now, there is no specific therapeutic drugs or vaccines for coronavirus infection, so it is especially important to study the structure, function, and pathogenic mechanism of novel coronavirus (also known as SARS-CoV-2). Biomacromolecule crystallography is a significant technique for the study of the high-resolution structure of biomacromolecules using crystal X-ray diffraction. Through this technology, the atomic-resolution crystal structures of SARS-CoV-2 3CL hydrolase (Mpro) and SARS-CoV-2-CTD in complex with hACE2 have been resolved.
Figure 1. The crystal structure of SARS-CoV-2-CTD in complex with hACE2. (Wang Q.; et al. 2020)
High-quality X-ray diffraction data can be further processed using available software to index and integrate into the data scale. Since the X-ray detector can only record the intensity, but not the phase of the electromagnetic wave, the phase determination is a key link in the crystal structure analysis. The crystallographers at Creative Biostructure will utilize different phase determination techniques to find the initial phases according to the specific situation of your coronavirus-related target protein. These techniques include molecular replacement (MR), multiple isomorphous replacement (MIR), single/multi-wavelength anomalous dispersion (SAD/MAD). We provide contract crystallization services to support phase determination, such as the acquisition of selenomethionine (SeMet) protein crystals.
After the initial phases are obtained, the electron density map can be calculated and the 3D structure model can be further reconstructed and refined, which is an iterative process until the R factor converges to a proper low value with an appreciable atomic model geometry. Through this data processing and analysis process, we will eventually deliver the high-quality electron density map, the biomacromolecule 3D reconstruction model, and complete statistical information. The quality of the final model will be verified by procedures such as PROCHECK.