In view of the threat to human health caused by bacterial antibiotic resistance, new strategy, such as anti-infectious compounds, are of high interest. Pseudomonas aeruginosa, a major cause of nosocomial infections, uses carbohydrate-binding proteins (lectins) as part of its binding to host cells. A soluble fucose-binding lectin, LecB, displays a unique carbohydrate-binding site that involves two closely located calcium ions bridging between the ligand and protein, providing specificity and unusually high affinity. Several high resolution X-ray crystal structures of LecB/fucose complex are available. However, the location of hydrogen atoms, that are crucial in the interaction mechanisms are not visible by X-ray crystallography.