Radiochemistry

• Isotopes

  Have a major use in labelling
• Labelling


  Targeting & tracking metabolites without altering their chemical properties (like a stamp)
• Origin of labelling

  Attach to a heavier group (e.g. phenyl) so it could be tracked more easily
• Problem with origin of labelling: may change chemical properties
• Labelling with isotopes

  More efficient because the chemical properties are similar/same
• Isotopes used in labelling

  • 13C used in NMR
  • 15N used to prove semiconservative replication
• If it has a half-life, it is radioactive
• Labelling in study of nitrogen in haemoglobin

  1. 14N was replaced with 15N

  2. It was found that glycine is where N atoms are derived from

  
• He found the lifeline of liver proteins are around 8 days

  
• Radioisotopes

  Unstable, release radiation to become stable isotopes

  
• Advantages of radioisotopes

  • Sensitive detection of chemical species, allows detection of small amounts (around 10-12 - 10-15)
• Disadvantages of radioisotopes

  • Toxicity, heavily regulated use only
• Types of radiation

  • Beta radiation
  • Gamma radiation

  
• Beta radiation


  Emits about 3MeV

  
• Scans using beta radiation

  Scans for active and inactive parts of the brain, images can be generated

  
• Ionising ability


  If a person was hyperthyroid, considerable loss of mass
• Radiation detected by Geiger counter

  • Alpha
  • Beta

  
• Penetrating ability


  Gamma can only be stopped by lead
• Radioactive decay

  Occurs exponentially
• Autoradiography

  1. Localise tracer e.g. carbon-14

  2. Wherever the carbon-14 is, beta radiation is being emitted and can be located