Labram hr

The P. aeruginosa 6294 cells were processed in a similar way to the zeta potential sample preparation and treated with the peptide at 1x and 2x MIC concentrations. The cell suspensions were then drop-casted onto clean aluminum foil mounted on the glass slide.^{16 (link)} Raman spectra were obtained in backscattering geometry using a LabRAM HR - Jobin Yvon (Horiba, Kyoto, Japan) spectrometer equipped with a Peltier-cooled CCD.^{16 (link)} A diode laser of wavelength 785 nm was used as an excitation source, and the light was focused on the sample using a 50× objective. All data were recorded within a wavenumber range from 800 to 1800 cm⁻¹.
For curve fitting, the Origin program was used. First, the baseline of the Raman spectra was processed by asymmetric least squares (ALS) method. The parameter for the asymmetric factor was kept 0.001, while keeping the threshold, smoothing factor and number of iterations at 0.05, 4 and 10, respectively. To reduce the noise and to get a clearer picture of the Raman shifts, further smoothening of the data was done by using Savitzky-Golay methods where the points of window were kept to 25 and the polynomial order was set at 5 without any boundary condition. The specific and significant Raman shifts of the different chemical groups and bonds were matched with a previously reported article by GB Jung et al.^{17 (link)}