Disperse Orange 3 as a resonance Raman probe for measuring membrane order

Abstract

Resonance Raman spectra of azobenzene derivatives were examined in the presence of lipid membranes to find a probe that can distinguish different membrane phases. The NO2 symmetric stretching band of 4‐(4‐nitrophenylazo)aniline, also known as Disperse Orange 3 (DO3), is downshifted by about 4 cm−1 on the phase transition of phosphatidylcholine membranes from the liquid crystalline to the gel phase. A comparable downshift also occurs when DO3 is bound to cholesterol‐containing membranes in the liquid‐ordered phase. Our results demonstrate that Raman spectrum of DO3 is a unique tool for measuring the molecular order of lipids in membranes.

Keywords

• Membrane order
• Disperse Orange 3
• Raman spectroscopy
• Resonance Raman probe
• Membrane microdomains