Measurement of GFP fluorescence is a useful tool for quantifying gene expression. When carrying out this type of work, researchers often wish to state their data as a measurement of fluorescence per cell. Currently, the fluorescence per cell measurement can be variable due to differences between:

• units of measurement
• data processing settings
• device model

To find fluorescence per cell values, typically the measured fluorescence is divided by the OD₆₀₀ as an approximation of a cell number. This can also be imprecise and variable when measured on different devices.

The aim of the Fifth InterLab study is to make fluorescence per cell measurements more compatible among various laboratories around the world by investigating the fluorescence of eight test devices built from BioBrick parts. By standardising the protocol for the plate reader calibration with LUDOX solution, silica beads, and fluorescein, we hope to reduce variability between our results and those of other iGEM teams. OD₆₀₀ values will be associated with colony forming units (CFUs) to achieve a more accurate measurement of fluorescence per cell.