Spectroscopic studies of stellacyanin derivatives

Two covalently modified derivatives of the apoprotein of the blue copper protein stellacyanin have been prepared. In one case, a dansyl group was linked to the cysteine at the copper binding site of apostellacyanin; in the other, a nitrophenol moiety has been attached to this same cysteine. Fluorescence yields and emission maxima of the dansylated protein and pK determinations of the nitrophenol group linked to the protein suggest that the solvent microenvironment at the copper binding site of apostellacyanin is quite similar to bulk water.