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You are here: Home / Research / Mechanisms / Cryptochromes

Cryptochromes

One of the candidate mechanisms for how magnetic fields might interact with the body

Cryptochromes are types of proteins (flavoproteins) which are present in plants, insects and mammals. They are blue-light sensitive components of the biological clock and two main forms have been identified, type 1 which are photoreceptive (react directly to light) and type 2 which are important regulatory factors in the biological clock controling daily biological rhythms.

Cryptochromes have been identified as a candidate for the mechanism by which migratory birds use the earth's geomagnetic field to navigate.  Research has shown that the magnetic compass in migratory birds is located in the eye and is light-dependent; the compass is more efficient when blue light is present. Given cryptochromes' sensitivity to blue light and their location in the retina of birds, they have become one of the leading candidates. Humans do not have these type 1 cryptochromes which are photoreceptive, but do have other photoreceptive pigments located in the retina.

Magnetoreception

The mechanism by which small changes in the earth's magnetic field translate into birds sensing these changes (magnetoreception) has been difficult to identify. Cryptochromes offer a potentially highly sensitive mechanism via a chemical reaction, known as the 'free-radical mechanism'.

When cryptochromes are activated by light, a radical pair is formed, which is two molecules each with unpaired electrons (called its active state). These electrons can spin in different directions resulting in different reaction products being formed. It has been hypothesised that magnetic fields may affect this reaction by altering or modulating the relative direction of the electron spins, therefore altering the length of time that cryptochrome remains in this active state. These differences in reaction products and rates are thought to translate to dark and lighter areas in the bird's visual sphere helping it identify inclination changes in the Earth's magnetic field.

Research investigating magnetic field effects on cryptochromes is ongoing. These free radical effects have been observed at high magnetic field strengths (thousands of microtesla), but have not been observed at low levels (tens of microtesla), similar to those that birds would use to navigate.  

See also:

  • A general discussion of mechanisms

Other particular mechanisms:

  • melatonin
  • free radicals

Biological clocks

All organisms exhibit rhythms in many things, from sleeping and eating to the timing of hormone release. Many of these rhythms are 24 h or "circadian", controlled by an internal biological clock. This self-sustaining clock is located in the hypothalamus and generates rhythms via oscillating gene and protein levels.

Latest news

  • New publication on cancer incidence from the UK electricity industry Cohort Study August 27, 2019
  • How has the reported risk for childhood leukaemia changed over time? February 11, 2019
  • Media stories about microshocks in children’s playground September 10, 2018
  • New studies on leukaemia and distance from power lines June 1, 2018
older news

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Navigation
  • What are EMFs
    • Terminology – an introduction
    • Electric fields
    • Magnetic fields
    • Units for measuring EMFs
    • Measuring and calculating EMFs
      • “EMF Commercial”
    • Adding fields together
    • Radiofrequencies
    • Screening EMFs
  • Sources
    • Overhead power lines
      • Fields from specific power lines
        • 400 kV
        • 400 kV – specific cases
        • 275 kV
        • 132 kV
        • 66 kV
        • 33 kV
        • 11 kV
        • 400 V/230 V
        • Replacing a 132 kV line with a 400 kV line
      • Summaries of fields from all power lines
      • Factors affecting the field from a power line
        • Voltage
        • Current
        • Clearance
        • Height above ground
        • Conductor bundle
        • Phasing
        • Balance between circuits
        • Balance within circuit
        • Ground resistivity
        • Two parallel lines
      • Calculating and measuring fields from power lines
        • Geometries of power lines
        • Raw data
        • On-line calculator
      • Fields from power lines – more detail on the physics
        • Field lines from a power line
        • The direction of the field from a power line
        • Power law variations in the field from a power line
      • Statistics of power line fields
    • Underground power cables
      • Different types of underground cable
      • Fields from cables in tunnels
      • Gas Insulated Lines (GIL)
      • Underground cables with multiple conductors
      • Effect of height on fields from underground cables
      • Screening fields from underground cables
    • Low-voltage distribution
      • UK distribution wiring
      • USA distribution wiring
    • House wiring
    • Substations
      • National Grid substations
        • Static Var Compensators
      • Sealing-end compounds
      • Distribution substations
      • Final distribution substations
        • Indoor substations
    • Transport
      • EMFs from electric trains (UK)
      • EMFs from cars
    • Appliances
    • Electricity meters
      • Smart meters
      • Traditional meters
    • Occupational exposures
      • Live-line work
      • Static Var Compensators
      • Occupational exposures on pylons
    • Field levels and exposures
      • Personal exposure
      • Other factors that vary with magnetic fields
      • Fields greater than 0.2 or 0.4 µT
    • Screening EMFs
      • Screening fields from underground cables
      • EMF Reduction Devices
  • Known effects
    • Induced currents and fields
    • Microshocks
      • Control of microshocks in the UK
      • Microshocks from bicycles
      • Bees and microshocks
    • EMFs and medical devices
      • Standards relating to pacemakers and other AIMDs
    • Effects of EMFs on equipment
  • Research
    • Types of research
    • Epidemiology
    • Animal and laboratory experiments
    • Mechanisms
    • Specific studies
      • UKCCS
      • CCRG
      • French Geocap study
      • CEGB cohort
      • Imperial College study
  • Current evidence on health
    • Childhood leukaemia
      • Survival from childhood leukaemia
      • Childhood leukaemia and Downs
      • Childhood leukaemia and night-time exposure
      • The “contact current” hypothesis
    • Other health effects
    • Scientific review bodies
      • WHO
      • IARC
    • Electric fields and ions
    • Comparing EMFs to other issues
  • Exposure limits for people
    • Limits in the UK
    • Limits in the EU
    • Limits in the USA
    • Limits in the rest of the world
    • Limits from specific organisations
      • ICNIRP 1998
      • ICNIRP 2010
      • NRPB 1993
      • NRPB 2004
      • EU 2004
      • EU 2013
  • Policy
    • UK policy
      • Power lines and property – UK
    • Compliance with exposure limits
    • European EMF policy
    • Precaution
    • SAGE
      • SAGE First Interim Assessment
        • Government response to SAGE First Interim Assessment
      • SAGE Second Interim Assessment
        • Government response to SAGE Second Interim Assessment
        • SAGE Second Interim Assessment – the full list of recommendations
  • Finding out more
    • EMF measurement and commercial services
    • Links
    • Literature
    • Contact us
  • Static fields
    • Static fields – the expert view