Cu2+ changes the intrinsic fluorescence spectrum of DMAV.
A, fluorescence spectrometry. Changes of the intrinsic fluorescence of DMAV (20 μmol/liter in 1 ml of TBS, pH 7.4) was estimated with emission at 346 nm and excitation at 278 nm. CuSO4 (1 mmol/liter in TBS) was added as 1-μl aliquots, resulting in final concentrations indicated in the figure. The final volume of CuSO4 was 18 μl. Li2SO4 (18 μl at 1 mmol/liter; final concentration 60 μmol/liter) did not affect the intrinsic fluorescence of DMAV (20 μmol/liter). B, the change in fluorescence was used to determine apparent KD. C, CuSO4 (60 μmol/liter) does not change the intrinsic fluorescence of an unrelated salivary protein (DM146; 20 μmol/liter) from D. maxima. A.U., arbitrary units.