Stained oil droplets were dissolved in isopropanol and quantified by measuring optical absorbance at 500 nm.
Virus titers were determined by measuring optical absorbance at A260 and by plaque-forming assays.
Cellular debris was pelleted by centrifugation and chlorophyll-a and -b levels were determined spectrophotometrically, in the supernatant, by measuring optical absorbance at 645 and 663 nm.
At day 8, differentiated cells were stained with Oil red O. C. Intracellular lipid accumulation was quantified by measuring optical absorbance at 500 nm (n = 3).
AP-activity was measured by adding 2× SEAP buffer (50 ml 2 M diethanolamine [pH 9.8], 50 µl 1 M MgCl2, 224 mg L-homoarginine, 50 mg BSA, 445 mg p-nitrophenylphosphate) and measuring optical absorbance at 405 nm every 15 s for 1 min. Antibody staining of these cells was done as follows: non-specific binding was blocked with 5% Normal Goat Serum in DMEM for 30 min at 4°C.
The wavelengths to measure the optical absorbance of intracellular proteins and nucleic acids in soluble cell lysates were 280 and 260 nm, respectively.
The concentrations of purified DNA were measured using a spectrophotometer (NanoDrop 2000, Thermo Scientific, Waltham, MA) with a wavelength of 260 nm, the appropriate wavelength to measure the optical absorbance of nucleic acids in soluble cell lysates.
For quantitative analysis, concentrations of extracted proteins and nucleic acids were evaluated using a spectrophotometer where 280 and 260 nm wavelengths were used to measure the optical absorbance of proteins and nucleic acids in lysates, respectively.
Beside other forms like INT, XTT and MTT, TTC is a standard indicator in biofilm growth experiments [ 38, 21, 39] measuring the optical absorbance.
The readings determining the cell viability were taken by measuring the optical absorbance at 450 nm.
