Micro Crystalline Sponge Method Combined with Small-Wedge Synchrotron Crystallography for Nanogram Scale Molecular Structure Elucidation

The crystalline sponge (CS) method enables X-ray structural analysis without the requirement of crystallization of the target compound. However, several technical and crystallographic challenges, such as low guest occupancy, static disorder, and crystal degradation, continue to limit both the accuracy and the success rate of the method. In this study, we explored the downsizing of CS crystals to the range of 1-10 μm to improve data quality and reduce the amount of sample required. By employing the small-wedge synchrotron crystallography method, which utilizes synchrotron X-ray sources and data merging techniques, we achieved significant improvements in structural accuracy and broadened the method's applicability, even to trace samples at the nanogram level (∼3 ng).