 This unusual observation was what lead Italian investigators to track down what was going on and lead to the discovery of apo A1 Milano (the city, Milano, ~160 km away, in which the researcher's lab was located).Biochemically, apo A1 contains an extra cysteine bridge, causing it to exist as a homodimer or as a heterodimer with apo A-II.However, the enhanced cardioprotective activity of this mutant (which likely depends on fat & cholesterol efflux) cannot easily be replicated by other cysteine mutants.