Ultrapure 1,5 diaminonapthalene (DAN) is an important matrix used in peptide and protein analysis by matrix assisted laser desorption ionization (MALDI) mass spectrometry. The matrix is effective in promoting reduction of disulfide bonds in the gas phase, which greatly facilitates analysis of proteins and peptides containing disulfide linkages.
Reduction of insulin using 1, 5 DAN Matrix
Insulin is composed of two peptide chains referred to as the A chain (21 amino acids - MW 2339) and B chain (30 amino acids - MW 3399). Insulin chains A and B are linked together by two disulfide bonds, and an additional disulfide is formed within the A chain. When insulin is spotted with CHCA matrix, the insulin subunits are poorly detected (upper panel). However, when insulin is spotted with DAN matrix, the disulfide bonds of insulin are cleaved during ionization, which releases the free A and B chains (lower panel).