3D electron crystallography of carbohydrates: structural diversity and radiation sensitivity – ECoCar

Carbohydrates, the most abundant and widespread biomolecules, present a remarkable diversity in chemical structures that results in even more diverse and complex higher-order structural features, from molecular conformations and interactions to assembly and packing manners. Many biological and material systems benefit from this structural complexity to obtain specific functionalities. Understanding the higher-order structural aspects is thus crucial to grasp their complex structure-properties relationships. Despite such importance, the structural diversity of carbohydrates has not been understood or even systematically described due to the lack of suitable analytical methods. The difficulty in preparing macroscopic carbohydrate crystals rules out the application of X-ray crystallography to these molecules, while their radiation sensitivity often limits the application of electron diffraction methods. The ECoCar project aims at shedding light on the structural diversity of carbohydrates by establishing chemical and higher-order structural relationships. For this purpose, we will use microcrystal electron diffraction (microED) and implement this approach to determine carbohydrate crystal structures. We will first optimize this method by quantitatively assessing both the global and local damage induced by electron irradiation in carbohydrate crystals with a wide variety of structures. Such information will serve as a solid basis for understanding the mechanisms of radiation damage of biomolecules. By taking advantage of the large collection of carbohydrate molecules available in the host institute, Cermav, and a long-lasting knowledge in carbohydrate crystallization, we aim at preparing 200 high-quality carbohydrate crystals for microED data acquisition. These include carbohydrates with different main-chain structures and side-chain chemical motifs, as well as various carbohydrate-solvent complexes. For comparative analysis, a structural database will collate all the crystal structures determined by microED. A better understanding of the structural aspects of carbohydrates will ultimately allow elucidating the structure-properties relationships of vastly diverse carbohydrate molecules, which is of paramount importance in biology and material sciences.