Ultrospec 2100 pro spectrometer

Four genetically engineered bioluminescent bacterial strains from E. coli were examined: DPD2794, TV1061, grpE::lux, and soxS::lux, which were received from Prof. Shimshon Belkin (Hebrew University, Jerusalem, Israel) [38 (link),39 (link),40 (link),41 (link)]. Firstly, they were grown overnight in 5 mL Difco^TM LB broth (20 g/L) supplemented with 100 μg/mL ampicillin on a shaker (Lumitron, Petah Tikva, Israel) at 120 rpm and 37 °C. A 100 μL aliquot (1/100 dilution) of the overnight-grown bacteria was subcultured in 10 mL LB broth on a shaker without shaking at 37 °C for 3 h. Then, the bacterial culture was centrifuged at 5000 rpm for 10 min, to achieve an optical bacteria cell density of 1.2 at 600 nm (OD₆₀₀). It was then diluted to the desired concentration of 1.0, 0.8, 0.6, 0.4, and 0.2, as determined in an Ultrospec 2100 pro spectrometer (Amersham, UK).

α-Chitin nano-fiber films with different charges were respectively prepared from two chitin nano-fiber dispersions of DEChN and TOChN. Chitosan film was prepared from the chitosan solution. The chitosan powder can be dissolved in water by adding a little amount of acetic acid of 2 % (wt). The chitin nano-fiber dispersions or chitosan solution were poured onto plastic plates, dried at 40 °C, and then the films could be obtained by peeling them from the plates. Moreover, the chitin(+)–chitin(−) composite film (DE-TO-ChN-F) of the positively charged DEChN and negatively charged TOChN was fabricated through the layer-by-layer approach of the two nano-fiber dispersions [39 (link)]. According to the assembled mechanism, the layer-by-layer composite film consisted of alternating layers of oppositely charged chitin nano-fibers. Light transmittance of the chitin nano-fiber films with the average thickness of 0.025 mm from 300 to 700 nm was determined by an Ultrospec 2100 pro spectrometer from Amersham Biosciences.