Question

Fungal laccase is approximately 0.4% copper by mass. What would be the minimum molar (empirical) mass, assuming 1 mol Cu/mol protein.

Answer 1

assuming 1 copper atom per protein gets us the link that 63.5g of each mole of this protein must be from copper. That 63.5g is 0.4% of the total mass. Find the total mass of which 63.5g is 0.4%.

Answer 2

I get about 15,875g/mol, which is about right for a protein that contains thousands of atoms in a single molecule.