Ls 45 fluorescence spectrometer

The FTIR spectra were recorded on Perkin Elmer Spectrum 100 FTIR spectrometer (4000–650 cm⁻¹) (Waltham, MA, USA). Absorption spectra of nanoparticles were measured in chloroform, using a Perkin Elmer Lambda 25 spectrophotometer (Waltham, MA, USA) at room temperature. Emission spectra of the particles were recorded on a Perkin Elmer LS 45 fluorescence spectrometer (Waltham, MA, USA), and the data was collected at room temperature. The pXRD analysis of the samples was recorded on a Bruker D8 advanced diffractometer (Billerica, MA, USA) using Cu Kα radiation. Samples were loaded on flat steel and scanned from 5° and 85°. The HRTEM images were obtained by a JEOL JEM-2100 electron microscope (Akishima, Tokyo, Japan). FESEM images were obtained by ZEISS FEGSEM Ultra plus (Oberkochen, Germany).

Fluorescence spectra were collected using a PerkinElmer LS 45 Fluorescence Spectrometer at an excitation wavelength of 290 nm. The emission spectra were recorded using a 1 cm path length quartz cuvette (3.0 ml) at wavelengths from 300 to 400 nm. The concentration of HSA was 1 × 10⁻⁶ M and CLO solution was added to HSA at various ratios (0.5 : 1 to 7 : 1) at 5 min time periods. Fluorescence measurements at the two temperatures of 286 and 310 K were obtained to probe the important binding forces and quenching mechanism of CLO–HSA. To investigate the conformational changes of HSA after addition of CLO, synchronous fluorescence spectroscopy (SFS) at different scanning intervals (Δλ = 15, 60) was used. It must be noted that for the Δλ = 15 nm measurements, the concentrations of HSA and CLO were 1 × 10⁻⁶ M and 4 × 10⁻⁶ to 2.73 × 10⁻⁵ M, respectively, and at Δλ = 60 nm the concentrations of HSA and CLO were 1 × 10⁻⁷ M and 8 × 10⁻⁷ to 3.8 × 10⁻⁶ M, respectively.

To evaluate the ability of FKFL-G2 to disrupt bacterial cell membranes, the membrane permeabilization assay was performed using N-phenyl-1-naphthylamine (NPN) [47 (link)]. E. coli and S. aureus bacteria were thawed and cultured overnight at 37 °C while being shaken at 180 rpm. After the absorbance of the bacterial solutions reached an OD₆₀₀ of 1.0, the bacterial cells were harvested via centrifugation at 3500 rpm for 10 min. The bacterial pellet was washed twice with 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) buffer (pH 7.8). The bacterial pellets were then subjected to another round of centrifugation at 3500 rpm for 10 min and resuspended in 1 mL of HEPES (pH 7.8) to make bacterial solutions. Lastly, a 1 mL solution, containing 880 µL of a given bacterial solution; 20 µL of 1mM NPN; and 100 µL of FKFL-G2, G2 PAMAM, kanamycin, and ampicillin (1 mg/mL), was prepared and incubated for 30 min. Triton X-100, a well-known surfactant with a high capacity to destroy cell membranes, was used as a control. The fluorescence of each solution was measured using a fluorometer (LS45 Fluorescence Spectrometer, PerkinElmer, Waltham, MA, USA) at an excitation wavelength of 350 nm and emission wavelength of 429 nm.

FMN or riboflavin (10 μM, final concentration) was injected into a quartz cuvette sealed with a rubber stopper and deoxygenated by purging with N₂ for 5 min. Deoxygenated cell suspension and sodium formate (electron donor) were injected into the quartz cuvettes to obtain a final concentration of ~10⁷ cells ml⁻¹ and 10 mM, respectively. The total volume of the aqueous phase in quartz cuvettes was 4 ml. Fluorescence (excitation, 263 nm; emission, 522 nm) was monitored every 5 min using a PerkinElmer LS 45 fluorescence spectrometer.