In a dot blot, macromolecules are applied directly to the matrix.
However, proteins with low molecular weight have a small affinity for nitrocellulose, limiting potential applications.
This defect may be remedied by glutaraldehyde, which can covalently bond proteins to nitrocellulose.
Another matrix is cellulose paper modified with diazophenylthiother, which can also facilitate covalent bonding of proteins.
Nylon membranes are also used for protein blotting, although they may result in the binding of anionic dyes such as Coomassie blue and Amido black.