Distance requirement for hydrogen bonding to occur
You will probably find all this information in biochemistry textbook. To give you an idea in proteins, typically; alpha helices H..O distance is 2.06 Angstrom, and N..O, 2.99. In beta sheets (parallel) H--O 1.97, N--O 2.29 and in anti parallel sheets, H--O 1.96 and N--OI 2.91. These H bonds are not linear, e.g C=O..H-N typically 150 to 160 degree for COH or NHO angle.

In Watson-Crick base pairing in DNA, (C-G pairs) the linear H-bond distances  are  $\mathrm{N_4-(H)-O_6}$ 2.91, $\mathrm{N_3-(H)-N_1}$ 2.95, and $\mathrm{O_2-(H)-N_2}$ 2.86.