Table 2.

Hard-sphere contact distances^*

	N	C(sp3)	C(sp2)	O	HN	H
N	2.57 Å	2.85 Å	2.71 Å	2.57 Å	2.32 Å	2.32 Å
				(2.33 Å)
C(sp3)		3.14 Å	2.99 Å	2.85 Å	2.52 Å	2.52 Å
C(sp2)			2.85 Å	2.71 Å	2.38 Å	2.38 Å
O				2.57 Å	2.32 Å	2.32 Å
					(1.71 Å)
HN					1.90 Å	1.90 Å
H						1.90 Å

^*All contact distances were obtained from Hopfinger (16) and softened by a factor of 0.95. Values in parentheses were used when the atoms in question are in a hydrogen bond.