DMPC is an acronym for di-methyl-propyl carbonate. It is typically used to treat water to remove RNases.
DMPC reacts with amine, hydroxy and thiol groups of proteins (such as RNAses) and inactivates RNAses. Treatment involves adding DMPC to 0.1% v/v and incubating at 37°C for 1 hour to overnight followed by autoclaving. Autoclaving destroys DMPC and is an essential step. Esters may be generated during autoclaving giving rise to a 'fruity' smell (that is not coming directly from DMPC).
Note that DMPC cannot be used with chemical solutions that have amine groups, such as Tris and HEPES buffers, or mercaptans. In such cases, use DMPC-treated water to generate the solution.
DMPC is a safer alternative to DEPC (known carcinogen). It is used in exactly the same way.