Table 4. Details of oxidation-binding modes for 2- or 3-fluorinated galactose.

	Galactose
	Productive 2-oxidation binding mode a								Competing binding mode
Variant	H167A		V546C		H450G		H450G/V546C		H167A		V546C		H450G		H450G/V546C
Ligand	3FGal		3FGal		3FGal		3FGal		2FGal		2FGal		2FGal		2FGal
Oxidation site	–		C2		C2		C2		C1		C1		C3		C3
Stereoisomer	–		β		β		β		β		β		αb		αb
Loop conformer	closed		semi-open		semi-open		semi-open		semi-open		semi-open		semi-open		semi-open
Sugar-protein interactions c	–	–	O1	V546 O	O1	V546 O	O1	V546 O	O1	H548 Nε2	O1	H548 Nε2	O1	D452 Oδ2	O1	D452 Oδ2
	–	–	–	–	O1	H548 Nε2	–	–	O1	N593 Nδ2	O1	N593 Nδ2	O1	T169 Oγ1	O1	T169 Oγ1
	–	–	O2	H548 Nε2	O2	H548 Nε2	O2	H548 Nε2	F2	Q448 Nε2	F2	Q448 Nε2	F2	Q448 Nε2	F2	Q448 Nε2
	–	–	O2	N593 Nδ2	O2	N593 Nδ2	O2	N593 Nδ2	F2	N593 Nδ2	F2	N593 Nδ2	–	–	F2	N593 Nδ2
	–	–	F3	Q448 Nε2	F3	Q448 Nε2	F3	Q448 Nε2	O3	D452 Oδ2	O3	D452 Oδ2	O3	H548 Nε2	O3	H548 Nε2
	–	–	–	–	F3	N593 Nδ2	–	–	–	–	O3	Q448 Nε2	O3	N593 Nδ2	O3	N593 Nδ2
	–	–	O4	D452 Oδ2	O4	D452 Oδ2	O4	D452 Oδ2	O4	D452 Oδ2	O4	D452 Oδ2	O4	V546 O	O4	V546 O
	–	–	O4	T169 Oγ1	O4	T169 Oγ1	O4	T169 Oγ1	O6	L545 O	O6	L545 O	–	–	–	–
	–	–	O6	Y456 Oη	O6	Y456 Oη	O6	Y456 Oη	O6	Y456 Oη	O6	Y456 Oη	O6	Y456 Oη	O6	Y456 Oη

^aThe following three criteria are considered consistent with a productive binding mode: (i) The sugar is oriented for oxidation at C2; (ii) the substrate-binding loop is in the semi-open conformation; (iii) the side chain Oγ1 group of Thr169 is pointing away from the flavin N(5)/O(4) locus.

^bThe ability of P2O variants to stabilize either the α- or β-anomer is uncorrelated to space group and crystal contacts, and depends solely on the new structural context provided by the mutation.

^cItalicized interactions represent interactions with the catalytic residues.