Table IV.

Statistics of Polygon Counts

	Number of polygon vertices
	3	4	5	6	7
Total count	14,555	3978	8114	5793	1324
% Total count	43	12	24	17	3.9
Average count per structure	9.3	2.5	5.2	3.7	0.8
Average % composition per structure	45	14	23	15	2.8

Total count is a total number of water polygons observed in the unit cell of 1561 structures processed. The average count per structure represents the average number of each polygon observed per structure. Average % composition per structure represents the average percent composition of each polygon per structure, and the protein crystals without any polygons were excluded from the calculation. The low values reflect the fact that most protein crystals do not have water polygons beyond the first water layer. Four hundred eighty structures (31% of the dataset) have no water polygons at all beyond the first water layer, but 72 structures (4.6%) have more than 100 total polygons beyond the first water layer in a unit cell. Most abundant water polygon was trigon followed by pentagon, hexagon, tetragon, and heptagon.