THE MANY AROMAS OF DIMETHYL SULFIDE: (CH3)2S

Generally, dimethyl sulfide has an unpleasant smell. It's described as 'rotten cabbage' or 'cooked cauliflower'. A source of it in cooking is the breakdown of the amino acids methionine and

S-methylmethionine

(shown in red and yellow respectively), which are present in large quantities in cabbages and Brussel sprouts. These have been drawn in the cooking pan with a fame sign above; this means that when the content of the pan is cooked, dimethyl sulfide is released (this compound is drawn on the flame sign).

At lower concentrations, dimethyl sulfide smells more pleasant. It can be found in wine and in some cheeses as well. When the cheese ripens, the enzymes break down proteins to give free amino acids and methionine (again in yellow) which are then transformed into several sulfur compounds, especially dimethyl sulfide. At low concentrations, dimethyl sulfide is also the smell of the seaside. The volumetric flask has wine inside it and, when it's poured in the beaker, it 'becomes' water. Wine and seaside have two distinctive smells, but they both have one component in common. Using a pinch of surrealism, wine turns into water.

Some other natural sources of dimethyl sulfide are not so attractive. The dead horse arum lily uses a cocktail of molecules, including dimethyl sulfide and polysulfides (the formula for sulfides is S2-, shown by the light blue colour), to attract insects for pollination (e.g a bee!). These are lured by a smell resembling rotten flesh.

Research shows that dimethyl sulfide is a key odour ingredient (along with H2S and CH3SH) of human flatulence and halitosis (bad breath). This is not shown in the piece.

Phytoplanktons are at the bottom of the ocean food web. They are a source of food for tiny zooplankton and enormous whales. Phytoplankton produces a substance called dimethylsulfoniopropionate (DMSP); this is shown in fuchsia. When phytoplankton are eaten by zooplankton (it's the tiny creature in the beaker) or small fishes, DMSP gets broken down to dimethyl sulfide, which attracts more zooplankton to feed. This dimethyl sulfide also attracts seabirds (hence why there's a toy hanging from above the beaker), penguins and seals (which poke their noses above the water's surface to smell the dimethyl sulfide).