Friday, November 25, 2011

Focus on Absorbance

A high power xenon flash lamp illuminates the sample using a specific wavelength selected by an optical filter, or the sample is measured over the entire visible spectrum using a UV/Vis absorbance spectrometer. Then a light detector located on the other side of the well measures how much of the initial light is transmitted through the sample: the amount of transmitted light is related to the concentration of the molecule of interest. Absorbance-based measurements are used for a variety of applications including:
  • 260/280 nm DNA quantitation 
  • Protein quantitation (e.g. Bradford Lowry, BCA) 
  • Reporter gene assays (e.g. ß-Gal, SEAP) 
  • Cell proliferation and apoptosis 
  • ELISA, enzyme immunoassays (e.g. alkaline phosphatase, horseradish peroxidase) 
  • Enzyme activity assays: Monitoring absorbance changes in cellular co-factors NADH and NADPH allowing the determination of enzymatic activity 
  • Reaction optimization (metallation of porphyrin in twelve different solvents) by parallel kinetic studies 
  • Microbial growth 
  • Protein aggregation 
  • Antioxidant capacity of substances using colorimetry 

BMG LABTECH offers a variety of microplate readers that can read in absorbance mode with an integrated UV/Vis spectrometer as well as filter based absorbance detection.

For more information on absorbance as well as a selection of absorbance application notes and compatible BMG LABTECH microplate readers visit:

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