Figure 1.

Organic solvents cause artificial colouration. (a) Yellow colour develops when the reaction mixture contains organic solvent (e.g. DMSO). The figure shows wells containing decreasing amounts of DOPC (from the top: 16, 8, 4, 2, 1, 0.5, 0.25 and 0 µg) before addition of the phospho-vanillin reagent (after 90°C 20 min incubation). Reaction mixtures in the wells of the left column do not contain DMSO while in the right column they contain 20 µL DMSO/well. (b) Absorbance at 540 nm (arb: arbitrary units). Background of the reaction before adding phospho-vanillin reagent without DMSO is indicated as “w/o DMSO” while background with 20 µL DMSO is labelled as “w DMSO”. Scale of Y-axis was set to the axis of a standard SPV assay. Insert panel shows the curves with a zoomed Y-axis to make the linearity visible. The figure shows the result of a single representative measurement.