Blog #12 - Glowing Vanilla pudding

By NBailly 16:16, June 02 2014 (CDT)

The topics of today's double lesson was quorum sensing as well as measurement of fluorescence. At the beginning of class, the students form 6 groups and start an experiment dealing with fluorescence: Each group weighs and dissolves 4g of vanilla pudding powder in 50mL of water. While conducting the experiment, each group is supervised by a member of our iGEM team.

Vanillepudding 1

While we give the powder some time to dissolve, René discusses the worksheet about quorum sensing that we gave out to the students last week. In doing so, the students learn what quorum sensing actually is, how it is used in different ways by a variety of bacteria, and how we want to use this function for our project.

Quorum Sensing Folie

Meanwhile the powder had dissolved in the water. Excess powder accumulated at the bottom of the beaker. Using a syringe, the students suck 2mL of supernatant out of the beaker, and press it through a filter into a cuvette. A part of our project involves the development of a fluorescence measurement device named "Cellock Holmes". Each group of students at a time places its cuvette in the "Cellock Holmes" prototype, and notes down the values displayed on the cellphone display. Of course, each group also measures the fluorescence of a positive (pure riboflavin in water) and a negative (chalk dust in water) control.

Measuring with Cellock Holmes

While the other groups wait for their turn, their supervisors explain the background of this experiment: The electrons in some molecules change into energy states when irradiated with electromagnetic waves. When returning to the normal state, the electrons dissipate excess energy, also in the form of electromagnetic radiation. This process is called fluorescence. Vanilla pudding contains the molecule riboflavin (vitamin B2). When riboflavin is irradiated with blue light, the molecule fluoresces green. The intensity of the green light is visually recorded by our device. Special software processes the data and the measured value is displayed on the cellphone connected to the device via Bluetooth. We will discuss the results of the experiment next class.