Table 3.

Bond-length and bond-angle values for polyalanine chains^*

Atom name	Atom description	Bond type	Bond length, Å	Angle type	Bond angle
C(sp3)	sp3 carbon atom	C(sp3)–C′	1.525	H–C(sp3)–C′	109.6°
C′	Peptide group carbonyl carbon	H–C(sp3)	1.08	C(sp3)–C′–N	116.2°
O	Peptide group carbonyl oxygen	C′–O	1.231	O–C′–C(sp3)	120.5°
N	Peptide group amide nitrogen	N–C′	1.329	O–C′–N	123.3°
Cα	Backbone α carbon	N–H	1.008	C′–N–H	119.15°
H	Hydrogen atom	N–Cα	1.458	C′–N–Cα	121.7°
		Cα–C(sp3)	1.521	N–Cα–C(sp3)	110.4°
		C–C′	1.525	H–C(sp3)–Cα	109.6°
		N–C(sp3)	1.458	C(sp3)–Cα–C′	110.5°
				Cα–C′–O	120.5°
				Cα–C′–N	116.2°
				C′–N–C(sp3)	121.7°
				N–C(sp3)–H	110.0°
				H–N–C(sp3)	119.15°
				H–C(sp3)–H	109.6°

^*Adapted from ref. 17. The torsion angle of the peptide unit is fixed at ω = 179.5°. See Table 1 for N–C_α–C bond angles (τ).