The contribution of Raman scattering to the fluorescence of the polyene antibiotic amphotericin B.

Fluorescence has recently been applied to the analysis of the molecular organization state of the polyene antibiotic amphotericin B (AmB) in solution or in lipid membranes. The polyene chain of AmB monomer gives rise to two fluorescence emissions; S(1)(2(1)A(g)) → S(0)(1(1)A(g)) between 500 and 700 nm, S(2)(1(1)B(u)) → S(0)(1(1)A(g)) between 400 and 500 nm. However, Raman scattering might interfere with the S(2) → S(0) emission fluorescence due to the weak fluorescence quantum yield and close proximity to the exciting lines. In fact, we show here that a change in the excitation wavelength results in a shift of three emission bands, an effect which excludes their assignment to fluorescence. These bands originate from the water Raman at 3382 cm(-1)and AmB resonance Raman at 1556 and 1153 cm(-1). As a consequence, some former conclusions on the molecular organization state of AmB should be reconsidered.