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Friday, June 21, 2013

Microdosimetry

Here is a nice collection of slides showing how much we know about radiation microdosimetry.

In particular, I like the third set (Nikjoo). Notice page 6 which contains a wealth of data on radiation interactions from the tissue down to the DNA molecule level.

Pages 20 & 21 show computer modeling of radiation interactions.

Page 38 shows the DNA damage from a single proton (SSB = single strand break, DSB = double strand break, BD = base damage).

Page 40 shows the level of detail we understand about one mechanism of DNA repair (often employed for DSB's) called non-homologous end joining.


3 comments:

  1. Yes, impressive.

    In there any information on the overall error rate of the NHEJ process?

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  2. I'm not a molecular biologist, but my understanding is that there is no overall error rate. That's because different mutagenic agents affect different genes as shown here (IR = ionizing radiation):

    http://www.nap.edu/openbook.php?record_id=11340&page=41.

    (This is also why a common claim made by hp deniers, that radiation is just a small insult compared to metabolic oxidative damage is false...different genes are involved, though there is some overlap. And there are more DSB's from radiation, than oxidative damage.)

    So depending on the study (cell line, agent used, cellular environmental conditions, etc.) one gets different results, like here:

    http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2840102/

    According to the National Academy Of Sciences BEIR VII, "sometimes" there's a loss or gain of up to 10 nucleotides, and "in some cases" NHEJ is responsible for large deletions and chromosome aberrations.

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  3. OK thanks. A while ago I went on a reading spree on this, and the end result was pretty much this.

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