The InterLab Study’s goal is to identify and correct the sources of systematic variability in synthetic biology measurements. Previous studies done by iGEM showed measuring GFP expression in calibrated absolute fluorescence units with a known concentration of fluorescent molecule, the variability was reduced between labs. However, when taking bulk measurements with a plate reader for a population of cells. The variability is still large for this measurement; the main source of variability is the number of cells in the sample.
The plate reader measures the fluorescence value as an aggregate measurement of the entire population of cells. To find the GFP per cell the total fluorescence must be divided by the number of cells. This is accomplished by measuring the absorbance at 600nm which is used to calculate the number of cells. However, the OD measurements are subject to high variability between labs and its results may not be accurate. Therefore a cell count for each sample was used to reduce the variability from the OD measurement.
Our results were inconclusive. When we turned in our data, we had originally made a few mistakes in the transfer of data from the readings to the spreadsheet. However, there were still errors in our results. Below are the figures and charts from our Interlab. We are unsure of what went wrong; however, we had some trouble understanding the protocol as well as Day 3 procedures being quite tedious. So a mistake could have been made on the last day of Interlab.