Binding of Al(III)-tetracarboxyphthalocyanine to hemoglobin and myoglobin.

The interactions between Al(III)-tetracarboxyphthalocyanine (AlPc(COOH)(4)) and hemoglobin (or myoglobin) have been studied. The results showed that AlPc(COOH)(4) effectively quenched the intrinsic fluorescence of Hb and Mb via static quenching. The hydrophobic and electrostatic interactions played a major role in stabilizing the AlPc(COOH)(4)-protein complex. The distance r between donor and acceptor was obtained to be 3.92 and 3.67 nm for AlPc(COOH)(4)-Hb and AlPc(COOH)(4)-Mb system, respectively. The effect of AlPc(COOH)(4) on the conformation of Hb and Mb was analyzed using UV-vis absorption spectroscopy, circular dichroism spectra, synchronous fluorescence and three-dimensional fluorescence spectra.