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.