X-Ray Databases

[Probeman]

Brian Joy and I were discussing x-ray databases under the topic of boron matrix corrections and I was reminded of a story that illustrates why it's important to have an accurate and complete x-ray database...

I cannot remember where I heard this story but some of you might remember about 20 years ago when there a story being circulated that one shouldn't cook with aluminum (or aluminium if you're a brit) , because they had found a link between Alzheimer's patients and high Al levels in the brains of such patients.

As is typical for medical researchers, they had treated the brain tissue with osmium tetraoxide for contrast in the TEM, and when they performed an EDS measurement, they thought they were seeing a small Al peak. But actually this is apparently what they were seeing:



According to the story their x-ray database did not contain Mz lines for Os.  Does any one else know more details about the story, for example whether it is true or not!  Because I have a hard time believe that would have not ruled out Al with other methods...

[Probeman]

I wrote Dale Newbury at NIST if he remembered anything about this story and indeed he did (Dale is a wealth of microscopy lore and legend- in my opinion he should be designated a National Treasure).  This is what he had to say:

This story is actually closely connected to the legendary Chuck Fiori, who while he worked at NIH revealed the Os-Al measurement problem to the biologists who were doing the Os-fixation and misinterpreting the spectrum as AlK instead of OsM.  However, there is more to the story.  Chuck subsequently worked with the NIH brain dementia researchers and using dehydrated but unfixed (no Os) brain sections did EPMA-WDS mapping of Al distributions (at 500 ppm with full background correction!) that showed close matching to certain critical nerve structures.  These were really heroic mapping efforts requiring many hours per map.  You can see these results in SEMXM-2nd edition page 541 or in Garruto et al., Proc. Nat. Acad. Sci. 81 (1984) 1875.

Actually, the researchers thought Al cookware wasn't particularly bad,  but Al-hydroxide tablets (e.g., Tums) to settle the stomach probably were not a very good idea.  Not much has ever come of this as far as I know.

I did some quick googling and I found no references to "Alzhiemer's aluminum osmium", but I did find this:

http://www.alz.org/alzheimers_disease_myths_about_alzheimers.asp

Note "Myth #4".  Also here:

http://www.ncbi.nlm.nih.gov/pubmed/12214020

It seems that this is a myth or a significant issue depending on what sources you cite...

[jon_wade]

yes, I'd heard about this from somewhere and it sounds plausible, given osmium tetroxide staining. 
So, while I am waiting for electrons to magically  make it down the column (ho ho bloody ho) I had a look...

how about:

doi:10.1016/S0140-6736(86)91303-6


"Lancet. 1986 May 3;1(8488):1033-5.
Confusion of osmium M-zeta with aluminium K-alpha lines in biological X-ray microanalysis."

[Probeman]

yes, I'd heard about this from somewhere and it sounds plausible, given osmium tetroxide staining. 
So, while I am waiting for electrons to magically  make it down the column (ho ho bloody ho) I had a look...

how about:

doi:10.1016/S0140-6736(86)91303-6


"Lancet. 1986 May 3;1(8488):1033-5.
Confusion of osmium M-zeta with aluminium K-alpha lines in biological X-ray microanalysis."

I'd say that you bloody nailed it!   
john

[jon_wade]

Turns out theres quite a lot of stuff published 'back in the day'.  Heres another:

http://jnen.oxfordjournals.org/content/jnen/24/2/200.full.pdf


Palade's solution, which my mad google-fu skills tells me is a buffered OsO4 solution, appears the culprit....

[Probeman]

Turns out theres quite a lot of stuff published 'back in the day'.  Heres another:

http://jnen.oxfordjournals.org/content/jnen/24/2/200.full.pdf


Palade's solution, which my mad google-fu skills tells me is a buffered OsO4 solution, appears the culprit....

Osmium Tetraoxide is nasty stuff as I'm sure everyone knows.

I once made a fused bead of Os from Os powder (it's almost the only way one can buy it due to the process that it is produced by and the fact that it has a crazy high melting point- over 3000 C).

The really nasty thing is that elemental Os converts to OsO4 merely in the presence of water vapor.  Even after the Os bead was mounted and polished, one could get a whiff of pungent OsO4 just by opening the sample container in a room with normal humidity, so it is kept in a dessicator needless to say.