Copper(I) transfer into apo-stellacyanin using copper(I)-thiourea as a copper-thionein model.

The direct incorporation of Cu(I) from [Cu(I)(thiourea)3]Cl, a structural analogue of Cu-thionein, into apo-stellacyanin, was successful both aerobically and anaerobically. A characteristic c.d. band of Cu(I)-stellacyanin at 270 nm (0 = -12.5 X 10(3) degrees X cm2 X dmol-1) was seen. On oxidation with hexacyanoferrate(III) or by air, the correct Cu(II) binding into the active centre of this 'Type 1' Cu-protein was deduced from chiroptical measurements which were supported by e.p.r. data. Thus Cu-thiourea turned out to be an excellent Cu(I)-donor in aqueous systems for the complete reconstitution of mononuclear Blue copper proteins.