Team:Hangzhou WestLake/Description

Project Inspiration and Description



Riboswitches are dynamic RNA molecules that recognize a wide variety of analytes found in cells such as metabolites, ions and even secondary messengers. Most riboswitches bind to their corresponding analytes and that invoke a conformational switch that subsequently regulates the expression of the downstream genes. This project explores the design and application of synthetic riboswitch that is capable of detecting environmental contaminants in resource limited settings. As a proof-of-concept design, we will focus on detecting polychlorinated biphenyls (PCBs), a group of manmade aromatic chemicals that had been widely used in many industrial processes and biomagnification of PCBs along the food chain. We will insert a previously discovered PCB aptamer either into the 5’-UTR of a bacterial reporter gene or downstream of the start codon (Figure 1).1,2 Aptamer binding to PCB will lead to its structural switching that leads to enhancement or reduction of gene expression. A reporter protein such as green fluorescent protein can be used as a readout to access the efficiency of the proposed system. Another possible (and instrument-free) readout could be the migration of bacteria,3 where E. coli can be reprogrammed to sense and migrate toward compounds using synthetic riboswitch.

What are PCBs?

  • A group of artificial industrial organic chemicals ( consisting of C, H, Cl atoms )
  • The number and locations of Cl atoms in the PCB molecules can determine its chemical and physical properties
  • No known taste or smell
  • Range in consistency from an oil to a waxy solid
  • Vary in toxicity
  • In the US, it was manufactured in 1929 until manufacturing was banned in 1979 but it is still being produced in other countries




What are the properties of PCBs?

  • Non imflammability
  • Chemical Stability
  • High boiling point
  • Electrical insulating


What are the Commercial uses of PCBs?

  • Heat transder and hydraulic equipment and capacitors
  • Electrical equipment including voltage regulators, switches, reclosers, bushing, and electromagnets
  • Plasticizers in paints, plastics nad rubber products
  • Pigments, dyes and carbonless copy paper
  • Oil used in motors
  • Adhesives and tapes




Why were PCBs banned in the USA?



PCB contamination is high in the Housatonic River and New Bedford Harbor in Massachusetts. Image Credit : U. S. fish and Wild life service

PCBs were banned in the US in 1979 amid suggestions that these chemicals could have unintended impacts on human and environmental health



Release and Exposure of PCBs

  • Non imflammability
  • Poorly maintained hazardous waste sites that contain PCBs
  • Illegal or improper dumping of PCB wastes
  • Leaks or releases from electrical transformers containing PCBs
  • Disposal of PCB-containing consumer products into municipal or other landfills not designed to handle hazardous waste
  • Burning some wastes in municipal and industrial incinerators

PCBs do not readily break down once in the environment. They can remain for long periods cycling between air, water and soil.



PCBs pollution can be found worldwide

  • Typically, PCBs are either broken down in the environment by sunlight or by microorganisms.
  • Because PCBs exist in sediments, scientists need to determine if it is better to dredge and remove contaminated sediments from waterways or if it is safer to leave the sediments in place and cover with clean sediments, allowing them to naturally biodegrade


Banned PCBs polluting West Africa may be from "illegaldumps"

PCBs contamination can be found in water, sediment (soil) and oil samples.


Why we start to design the project?

The use and production of PCBs and PCB containing materials span over decades which make the accurate detection important for the environment and human health.