The dimensions of a fully extended polypeptide chain are shown in Figure 3.2. The two adjacent α-carbon atoms are placed at a distance of 0.36 nm.

α-carbon—N^(NH₃) = 0.147 nm
α-carbon—C^(COO) = 0.153 nm
C—O = 0.123 nm
(Peptide bond)   C—N = 0.132 nm
N—H = 0.1 nm

Figure 3.2 Dimension of a Fully Extended Polypeptide Chain