Topic: Episode #356

[ktb973]

The Skeptics Guise to the Universe or the Skeptics Guys to they Universe?  I notice Steve changed the title this week.   

[Trinoc]

I live in Washington State and well remember when those laws against hunting Bigfoot were passed. The goal was not to preserve the mythical animal, but out of fear that someone would get shot. Yahoos were grabbing their rifles and taking to the hills with the intention of "proving" Bigfoot exists by shooting one of 'em. It seems like every year someone around here gets killed by some hunter mistaking them for a bear.

So far as I know, it's still okay to shoot unicorns here, so long as they're in season and you have the proper tag.

The Hunting Song-Tom Lehrer

[GodSlayer]

The Skeptics Guise to the Universe or the Skeptics Guys to they Universe?  I notice Steve changed the title this week.   

LOL I noticed that, too. (though I thought 'the Skeptic Skies to the Universe')

[rwh]

When Jay was taking about Neil deGrasse Tyson having his own theme music at the end of Who's that Noisy, I immediately thought of the Family Guy episode where Peter wishes for his own theme music.

Family Guy-Peter wishes for his own theme music

 

Rob

[Mormegil]

Just to clarify, the helical structure (or "Watson-Crick" structure) of DNA wasn't discovered using x-ray crystallography (as Dr. Novella mentioned), but x-ray diffraction.  The DNA was in solution, and not crystallized. 

X-ray crystallography is x-ray diffraction photography performed on crystallized substances (typically purified proteins).  Getting proteins to crystallize is an entire art in itself.  Interpreting the x-ray diffraction pattern into an 3D electron density map is another art.  Then fitting a chain of amino-acids (essentially a protein) into that 3D density map is another art in itself. 


Edit: I could be wrong about it not being crystallized.  That's what I recall from my structural class 10 years ago.  It's not clear in the original, extremely short 1953 paper (no Materials and Methods).

[Trinoc]

Just to clarify, the helical structure (or "Watson-Crick" structure) of DNA wasn't discovered using x-ray crystallography (as Dr. Novella mentioned), but x-ray diffraction.  The DNA was in solution, and not crystallized. 

X-ray crystallography is x-ray diffraction photography performed on crystallized substances (typically purified proteins).  Getting proteins to crystallize is an entire art in itself.  Interpreting the x-ray diffraction pattern into an 3D electron density map is another art.  Then fitting a chain of amino-acids (essentially a protein) into that 3D density map is another art in itself. 


Edit: I could be wrong about it not being crystallized.  That's what I recall from my structural class 10 years ago.  It's not clear in the original, extremely short 1953 paper (no Materials and Methods).

I thought you could only do x-ray diffraction to determine molecular structure on crystals, because the diffraction pattern comes from a mass of more or less perfectly aligned copies of the same molecule. Surely molecules in solution would just diffract x-rays all over the place and not produce an image. How on earth you can make a long, bendy molecule like DNA form into crystals beats me, though.

[willradik]

Poor Rosalind Franklin. She was indeed using X-Ray crystallography. Apparently her research was also appropriated by Wilson, Watson and Crick without her consent. When she did die, it was of cancer from overexposure to the X-rays.

[Chew]

When she did die, it was of cancer from overexposure to the X-rays.

It might have been from x-rays. It is impossible to state someone died from cancer caused by x-rays. At best you can make a probability statement. Cancer also ran in her family.

[willradik]

When she did die, it was of cancer from overexposure to the X-rays.

It might have been from x-rays. It is impossible to state someone died from cancer caused by x-rays. At best you can make a probability statement. Cancer also ran in her family.

Agreed.

[zen_arcade]

Franklin was originally diagnosed with ovarian cancer, and as others have pointed out, the disease also ran in her family. It's possible her work with x-rays contributed to her developing cancer, but it's my impression (and I may very well be wrong here) that an x-ray machine focuses an enormous amount of energy in a very narrow beam so unless she was frequently aiming the device at her abdomen I am skeptical of the claim that her cancer was caused by her crystallography work. Then again, I have no idea what radiation safety measures were in place at King's College in the early 1950's. Anybody know more about this?

[Mormegil]

Just to clarify, the helical structure (or "Watson-Crick" structure) of DNA wasn't discovered using x-ray crystallography (as Dr. Novella mentioned), but x-ray diffraction.  The DNA was in solution, and not crystallized. 

X-ray crystallography is x-ray diffraction photography performed on crystallized substances (typically purified proteins).  Getting proteins to crystallize is an entire art in itself.  Interpreting the x-ray diffraction pattern into an 3D electron density map is another art.  Then fitting a chain of amino-acids (essentially a protein) into that 3D density map is another art in itself. 


Edit: I could be wrong about it not being crystallized.  That's what I recall from my structural class 10 years ago.  It's not clear in the original, extremely short 1953 paper (no Materials and Methods).

I thought you could only do x-ray diffraction to determine molecular structure on crystals, because the diffraction pattern comes from a mass of more or less perfectly aligned copies of the same molecule. Surely molecules in solution would just diffract x-rays all over the place and not produce an image. How on earth you can make a long, bendy molecule like DNA form into crystals beats me, though.

I believe I was correct (mostly, the DNA was in a suspension, not solution).  Franklin's famous "Photo 51" was made with long DNA fibers aligned as best as possible, to produce the relatively "smeary" famous image.  According to the Bioinformatics website, DNA wasn't crystallized until the 1980s.

Here's a link that explains it better than I can: The DNA X-Ray Diffraction Technique.

[Mormegil]

Poor Rosalind Franklin. She was indeed using X-Ray crystallography. Apparently her research was also appropriated by Wilson, Watson and Crick without her consent. When she did die, it was of cancer from overexposure to the X-rays.

She was an x-ray crystallographer, pioneering work on Tobacco Mosaic Virus, but did not used crystals in the DNA study.

[willradik]

Poor Rosalind Franklin. She was indeed using X-Ray crystallography. Apparently her research was also appropriated by Wilson, Watson and Crick without her consent. When she did die, it was of cancer from overexposure to the X-rays.

She was an x-ray crystallographer, pioneering work on Tobacco Mosaic Virus, but did not used crystals in the DNA study.

Well I never said when or what for. I just said that she "was indeed using x-ray crystallography". 

[stugminto]

I wish I had something cool to say.

[GodSlayer]

I wish I had something cool to say.

why not just say something boring and obscenely educated like everybody else?