Outer membrane permeabilization by peptides cf. antibiotics at their corresponding MICs.

The uptake of the fluorophore NPN in the presence of different antibiotics and synthetic peptides was determined by assessing increased fluorescence at an excitation wavelength of 350 nm and an emission wavelength of 420 nm due to partition of the normally impermeable hydrophobic NPN into bacterial membranes. Relative fluorescence values of at least three biological replicates were determined by subtracting the fluorescence value without test substance.