IGEM:IMPERIAL/2006/Calendar/2006-7-19

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2pm: Meeting with Professor Tony Cass

  • Discussion on biosensors with Christin, Farah, Jonny, John (and Vincent)
  1. Project Overview: Oscillator_Overview
  2. Specification Document: Specifications_BioElecInterface

Summary of the meeting

  • Duration of meeting: 1:15 h

Suggestions on biosensors from Prof T. Cass:

  • Since we are limited to using E.coli, attempting to secrete proteins would be difficult. (Proteins can be transported into the periplasm, however, even with secretion tags, they cannot cross the outer cell wall.)
  • Small molecules diffuse to the extracellular environment quite easily in E.coli. However, these are often nutrients etc. for which the concentrations will vary throughout and not remain stable
  • Idea 1: Sensing pH
    • There are enzymes that hydrolyse lactones (e.g. AHL !!). For example, there are commercially available esterases (these are non-specific). It may be possible to find more specific enzymes that target lactones, or even specifically AHL.
    • By hydrolysing lactone, protons are generated and detected by a small solid state pH sensor (SFET)
    • The electrode (SFET) is coated with the enzyme and thus hydrolyses the lactone, causing a local pH change, which is proportional to the amount of AHL present
    • Measurements can thus be taken spatially (across the petri dish) and temporally
    • Need to have a buffer in the medium
    • Sensitivity of the sensor and the diffusivity of the proton have to be sufficient to allow the measurement of the pH change
  • Idea 2: Luminescent bacteria
    • Use luciferin (a pigment) and luciferase (enzyme which oxidises luciferin) to generate bioluminescence depending on varying concentrations of AHL
  • Idea 3: Generating current from glycolysis knock-out
    • Glycolysis is a series of redox-reactions. If an enzyme catalysing these reactions is knocked out, glycolysis cannot proceed.
    • The electron that is being transferred is then picked up by an electrode, generating a current that is proportional to the speed of glycolysis
    • Meanwhile, a pentose-phosphate pathway could be used by E.coli as nutrient
  • We can consult David Leek for some further information on Molecular Cell Biology

5.30pm: GSEPS Research Students' Research Symposium 2006

  • The keynote speech will be given by Professor Richard AL Jones, an experimental polymer physicist from the University of Sheffield. Professor Jones has recently published "Soft Machines: Nanotechnology and Life", a book which explains nanotechnology for the general reader.
  • location: - Read Lecture theatre, Level 5, Sherfield Building.
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