7A60.XX DNA Optical Transform Kit
X-ray diffraction, DNA structure
This kit demonstrates the X-ray diffraction of DNA by using patterns scaled up to diffract using laser pointers. The slide has 12 patterns to contrast between changing amplitude, period, and offset of the sugar-phosphate backbone shapes, as well as seeing only the effect of the base pairs or phosphate groups.
-  DNA optical transform kit
-  Green laser pointer
- Lasers can cause blindness. Use with caution.
- Shine the laser through various patterns as you discuss them.
- Slides A, B, and C show that diffraction off of lines gives an array of dots perpendicular to the lines.
- Slides D → G and E → H show that the X structure in the DNA diffraction pattern is caused by the helical structure of the sugar-phosphate backbone. The angle the X makes relates to the helix radius.
- Slides D → E and G → H show that changing the periodicity of the helix changes the spacing of the horizontal layer lines.
- Slides H → I show how having a double helix can make layer lines disappear.
- Slides F → I → L show how changing the offset between the two helices makes different layer lines disappear. L has the proper DNA helix offset.
- Slide K shows the diffraction pattern of the phosphate groups alone.
- Slide J shows the diffraction pattern of the base pairs alone.
- PIRA 7A60.XX
- A.A. Lucas et al., J. Chem. Ed. 76, 378 (1999)
- Don't attempt this at home!
- Original construction: purchased from the Institute for Chemical Education.
If you have any questions about the demos or notes you would like to add to this page, contact Ricky Chu at ricky_chu AT sfu DOT ca.