MicroED for Structural Analysis

Structure resolution is an important part of drug production and research, but in the early stages of drug discovery, large quantities of high-purity samples are often not available for single-crystal culture and structure resolution. This slows down the overall drug discovery process to a certain extent, and scientists may have to spend a lot of effort on optimizing the process conditions to obtain a large number of high-purity samples to eventually achieve the goal of structure elucidation.

Microcrystal electron diffraction (MicroED) is an evolving technique that combines Cryo-EM sample preparation methods with X-ray crystal diffraction data analysis to resolve the protein structure of nanocrystals. The elimination of the need to invest significant time and cost to prepare larger-sized crystals greatly simplifies the sample preparation process and significantly reduces the amount of sample required. This makes MicroED ideal for analyzing the structures of rare and valuable samples, and for analyzing larger numbers of samples in a short period.

Figure 1. MicroED for small-molecule structure determination. (Kunde, T., et al., 2019)

MicroED technique uses the interaction of electrons with the sample to obtain the diffraction data of the sample, and then the structure of the sample is obtained by the corresponding software analysis reduction. Since the electron wavelength is shorter, the electron-atom interaction is stronger and the sample diffraction is more powerful, so high-quality diffraction data can be obtained from a small number of nanometer-sized crystals using the MicroED technique. This is very suitable for the structural analysis of drug molecules or natural products with very small sample sizes and only nanocrystals are available. With MicroED you can cross the barrier of process optimization during early drug discovery and achieve structural resolution of compounds with only a tenth of the sample required for conventional single-crystal incubation.

Service flow from sample to structure

• Sample preparation. We want the sample to be in the form of a powder, which needs to contain microcrystals, the presence of which can be confirmed by X-ray powder diffraction. The conventional way is to put a small amount of powder on a TEM grid, freeze it with liquid nitrogen, and then put the grid into an electron microscope for imaging.
• Data acquisition. The grid view at low magnification may show hundreds of crystals, and the most time-consuming task is to identify those perfect crystals that have high-resolution diffraction. The diffraction data will be acquired automatically on our electron microscope.
• Data processing. The data processing process is very similar to conventional x-ray crystallography.
• Structure determination. The phase problem can be solved by the direct method, double space method, and molecular substitution method. An initial model is constructed and the structure is further optimized, during which all atoms will be assigned and evaluated for consistency based on the information provided by the customer.

Technology advantages

• Much lower sample requirements, only 100 mg of sample is needed for crystal culture.
• The requirements for crystal size are relatively low, with nanocrystals being sufficient for testing.
• For compounds that can only form small crystals, it is possible to give information on the structure and crystalline shape of the compound.
• It can be used to examine the structure of secondary products in the CMC process.

Creative Biostructure uses MicroED technology to obtain high-quality diffraction data with only a small number of samples cultured to produce nanocrystals. This greatly reduces the number of samples required for single-crystal incubation, which is very suitable for synthetic drugs or natural products with small sample sizes and provides a new way to analyze the structure of synthetic drugs and natural products. Please feel free to contact us to start your journey of high-resolution small molecule structure analysis.

Ordering Process

Reference

1. Kunde T, Schmidt B M. Microcrystal electron diffraction (MicroED) for small‐molecule structure determination. Angewandte Chemie International Edition. 2019. 58(3): 666-668.