Table 2. Properties of Small Molecule Binding Sites in Av1 and Cp1 Xe-Pressurized Crystals.

						distancea (Å) to
crystal	site	displaced species in native protein	B-factor (Å2)	occupancy (%)	peak heights in anomalous Fourier map (σ)	FeMo-cofactor	surface
Av1-Xe (4WNA)	Xe1	fills empty pocket	27.30	77	18.51	11.2	10.9
			28.16	81	20.23
	Xe2	HOH	31.29	49	8.48	15.1	0
			31.40	46	7.12
	Xe3	imidazole	31.48	62	9.62	33.1	0
			29.51	54	10.84
Cp1-Xe (4WN9)	Xe1	HOH	41.89	28	5.20	28.1	0
			39.52	34	5.78
	Xe2	MPD	64.15	46	5.93	23.8	0
			44.89	50	7.64
	Xe3	HOH	29.20	22	4.18	13.6	7.4
			33.79	19	5.53
	PRL	HOH	20.65	100	N/A	24.5	7.7
			23.76	100	N/A

^aDistances were measured from Xe or PRL to the closest nonsolvent atom in the FeMo-cofactor and at the protein surface.