User guide

Insulin consists of two chains, an A chain and a B chain, connected by disulfide bridges.
A chain
GIVEQCCTSICSLYQLENYCN
B chain
FVNQHLCGSHLVEALYLVCGERGFFYTPKT
You can build these chains either by copying and pasting the above text using the Paste Special>FASTA Peptide
command or by using the Biopolymer toolbar to build each chain.
To build intra-sequence disulfide bridge:
Select the single bond tool, then draw a bond between the C(6) and C(11) residues in the A chain, as shown below:
To build inter-sequence disulfide bridges
Select the bond tool and draw a bond between the C(7) in A chain and C(7) in B-chain. Draw another bond between
the C(20) in A chain and C(19) in B chain.
Lactam bridges
You can draw lactam bridges between Lys-Asp and Lys-Glu residues. The residues connect via amide bonds
between side chains. You can also mix disulfide and lactam bridges.
To draw a lactam bridge:
1. Draw a sequence that contains Lys and either Asp or Glu.
2. Using solid bond tool, draw a bond from Lys to the other residue. An example is shown below:
ChemBioDraw 13.0
Chapter 5: Drawing biopolymers 75 of 401