Originpro 8

Spectra were collected in SpectraSuite and processed in OriginPro 8.6. A baseline was drawn over the raw spectra, omitting the attenuation peaks. The spectra were then divided by the baseline, resulting in a change in the axes from intensity versus wavelength to transmission percentage versus wavelength. This processing allowed for quantification of attenuation depth (loss of transmission) and attenuation peak wavelength. OriginPro 8.6 was then used to find the peak wavelengths, using the ‘peak finder’ function. The peak wavelength was the wavelength at which the highest loss of transmission occurred, i.e. the apex of the peak. Spectra processing and peak wavelength finding were performed on all collected spectra, for both the calibration and the P. aeruginosa culture experiments, for both attenuation bands/peaks in the optical spectra. Wavelength shift was calculated for each peak using equation 1: $$\Delta \lambda ={\lambda }_{\text{t}/\text{c}}-{\lambda }_0$$
Where Δλ is the wavelength shift, λ_t/c is the peak wavelength at time t (for exposure to bacteria culture medium) or concentration c (for the sodium chloride calibration) and λ₀ is the peak wavelength at 0 h (bacteria) or 0% w/v (sodium chloride). Wavelength shift was then plotted against concentration or time respectively.