Absorption and fluorescence of fluram-labelled lysozyme and peroxidase solutions

The absorption spectra of fluram, lysozyme, horse-radish peroxidase, and mixtures of lysozyme + fluram and peroxidase + fluram and the fluorescence and fluorescence excitation spectra of the mixtures in 0.05 M phosphate buffer with 1 per cent dioxane are determined. Due to formation of a protein-fluram compound, the absorption spectra of the mixtures are not algebraic sums of the components. From the fluorescence intensities the number of bonding sites is found 6 in both cases. The fluorescence spectrum of the peroxidase-fluram compound has maxima at 305, 350, 400, 450 nm due to peroxidase and at 480 nm originating from fluram. In mixtures of 10(-5) M lysozyme + 10(-4) M fluram, 3/4 of the excitation energy is transferred from lysozyme to fluram within the compound under 280 nm excitation. Under similar conditions 4/5 of the excitation energy is transferred from peroxidase to fluram.