Table 1.

Stable intermolecular hydrogen bond pairs observed in the MD simulations for the Siglec-8 – 6’-sulfo-sLe^x and the Siglec-9 – 6-sulfo-sLacNAc complexes.

Ligand		Siglec-8 – 6'-sulfo-sLex	Siglec-9 – 6-sulfo-sLacNAc
Carbohydrate - Protein Interactions
Neu5Ac	O1a	R109 - Nη1, 3.0 ± 0.1b(89)c, d	R109 - Nη1, 2.9 ± 0.1 (100)e
		R109 - Nη2, 2.9 ± 0.1 (100)d, e	R109 - Nη2, 3.0 ± 0.1 (100)e
	N5	K116 - O, 2.9 ± 0.1(88)d	K116 - O, 2.9 ± 0.1 (90)
	O7	Y7 - Oη, 3.0 ± 0.1 (34)d	--f
	O8	Y58 - Oη, 3.1 ± 0.1(42)	N118 - O, 3.0 ± 0.1 (81)
		S118 - N, 3.1 ± 0.1 (65)d
	O9	S118 - N, 3.0 ± 0.1 (33)d	--
Gal	O4	--	D58 - Oδ, 2.8 ± 0.1 (100)a, e
	O6	--	T57 - N, 3.1 ± 0.1 (65)
Sulfate - Protein Interactions
6’-sulfo (6-sulfation in Gal)	Oa	R56 - Nη2, 3.0 ± 0.1 (76)d
		R56 - Nε, 2.9 ± 0.1 (59)d
		Q59 - Nε2, 3.0 ± 0.1 (58)d
6-sulfo (6-sulfation in GlcNAc)	Oa	--	N118 - Nδ, 3.0 ± 0.1 (74)
		--	K120 - Nζ, 2.9 ± 0.1 (64)

^awhen multiple hydrogen bonds are formed between multiple equivalent heavy atoms, the occupancy of the interaction listed is the sum of all the individual hydrogen bonds and the distance is the average of all the individual hydrogen bonds.

^bdistance in Å.

^cpercentage (%) based on a distance between non-hydrogen atoms of less than 3.5 Å.

^dalso observed in experimentally measured structure (PDB ID: 2N7B).

^ethe occupancy of the interactions between multiple equivalent heavy atoms, calculated as the sum of all the individual hydrogen bonds, is greater than 100%.

^fno stable interactions observed.