x ray diffraction


First Time Humans Saw the Structure of DNA - the photograph that revealed the Geometry upon which all Life is based.

Photo 51 is the nickname given to an X-ray diffraction image of DNA taken by Raymond Gosling in May 1952, working as a PhD student under the supervision of Rosalind Franklin. It was critical evidence in identifying the structure of DNA.

Working in the lab alongside Wilkins in 1952, Franklin had taken a startling, high-resolution photograph of a piece of DNA using X -ray crystallography, a technique whereby X -rays are shone on a crystalline structure (in this case, the DNA protein), to create a scattered reflection pattern on film.To the naked eye the photo looked merely like an X diced up into bits, but to Franklin it confirmed that DNA was a double-helix.

Photo 51 has an important place in history and has at least a claim to be the most important image ever taken.


you know what really grinds my gears? people excluding Rosalind Franklin from the discovery of the DNA double helix due to HER revolutionary photo in which she used x-ray diffraction, which is super dangerous by the way. don’t deny Rosalind Franklin credit for this crucial scientific discovery!!

Ok so some of you remember the crystallization stuff from my field study that I posted

Well it turns out today I got to take a much closer look at the crystals I made and shoot them through the X-ray machine.

So here’s one of the tubes with the MANY crystals of hemoglobin (with the drug). I showed you something like that last week.

I got to use the microscope to look at them up close and pick a good enough crystal to shoot through the X-ray diffraction machine. 


So the crystal we picked went under a glycerin/mother liquor solution to protect it from breaking down. (Below: the crystals on the left, the solution on the right, and the original mother liquor is behind the solution) 

Mother liquor is the liquid leftover after a crystallization btw.

So the crystal was picked up with a really tiny “lasso” tool so it could be hooked up onto the X-ray machine.

That tiny, pointy thing has a REALLY small hoop at the tip of it to pick the crystal up.

here’s a pic of it up close; that’s how small the hoop and crystal is

and this is the X-ray diffraction machine. 

The crystal is held up here:

and this “shoots” towards the crystal which lets it’s X-rays scatter and that gives us information on the crystalline structure. That ultimately lets us know about the structure of the individual molecules. 

Here’s an up close look at the crystal that was picked:

That’s after it was mounted on the X-ray machine. It’s hard to see cause it’s in front of the black screen.

and that’s the “X-ray” of the crystal we got. The individual dots are the individual components of the crystal. (We actually diffracted a second crystal to get a better x-ray because the dots were too close together on this one). This basically lets us see each unit cell of the crystal itself which would contain a repeat of the hemoglobin molecule with the drug/compound in this case.

By next week, I’ll be able to take a look at the actual protein structure of the Hb molecule and the drug and see how they bind together.


February 28th 1953: Watson and Crick discover DNA structure

On this day in 1953, scientists James D. Watson and Francis Crick discovered the chemical structure of DNA. They made the discovery of the double helix structure whilst building a cardboard model of the molecule in their laboratory at Cambridge University. Their model of DNA was based on an X-ray diffraction image taken by Rosalind Franklin and the fact that DNA bases are paired. They first announced their discovery to friends and it was not formally announced to the wider scientific community until April 25th. Watson, Crick and Maurice Wilkins were jointly awarded the 1962 Nobel Prize for Physiology or Medicine for their discoveries. The discovery was a groundbreaking moment for science, and lay the foundations for the research into DNA and the investigation of human genetics.

“We have found the secret of life.”
- Francis Crick

I finally found a solvent mixture that can be used to crystallize one of the most interesting thermofluorescent compound (it changes it’s emission under UV light when cooled or warmed). Now I only need to grow small single crystals for an X-ray diffraction to know the exact structure of this compound.

Want to know a bit more about thermofluorescence? Just check out these posts: http://labphoto.tumblr.com/tagged/thermofluorescence