Talk:X-ray crystallography

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Help with this template Comments: edit – history – watch – refresh The single crystal diffraction section needs a discussion of inorganic materials (e.g. that XRD is used extensively in silicon and compound semiconductor work).

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Article Grading: The following comments were left by the quality and importance raters: (edit · refresh) The single crystal diffraction section needs a discussion of inorganic materials (e.g. that XRD is used extensively in silicon and compound semiconductor work).

I think protein crystallography should have its own page (possibly redirected to from 'macromolecular crystallography') -- different refinement approaches, different ways of phasing, much more trouble with crystal growth ... Fivemack 15:55 21 September 2006

Dear Chemgrrl et al:

When use XRD to characterize CNTs, is the "d" in Braggy Eqn. the diameters of CNTs?--Lin

A little discussion about your rather major changes to this page would be appreciated! I would argue that the crystallisation and data processing of small molecules and the crystallisation and data processing of macromolecules, whilst being superficially similar, are sufficently different to merit their separate sections, as I had originally laid out. I suggest we combine our efforts and deliniate Small molecule and macromolecular crystallography whilst highlighting the differences and similarities between the two disciplines... Bassophile 20:20, 28 March 2006 (UTC)

Hi The Spirit. I'd appreciate any assitance/comments/criticism you have... I think it's a little patchy at the moment. I'm trying NOT to include too much nasty theory, but I suppose some is inevitable. I'm also trying not to duplicate what has already been done elsewhere. There is a nice section on unit cell which includes a good introduction to symmetry etc, which is why I've left that out. I've also not gone into Bragg's and Laue's laws/conditions as they too are covered elsewhere. Let me know what you think so far.

Cheers, Bassophile 15:30, 14 February 2006 (UTC)

Hi Bassophile, I also did X-ray crystallography for a living (still do sometimes). I worked at the Weizmann Institute of Science and contributed to set up it Structural Proteomics Center. I would be wiling to assist you in expanding the X-ray crystallography page, especially the biological crystallography (and crystallization) sub-points.

All the best, TheSpirit 13:58, 14 February 2006 (UTC)

Hi everyone. I am considering doing a fairly major edit of this page. I do this (biological crystallography) for a living and am more than happy to spend some time putting more about it in the public domain. This is fairly complicated area, and I am happy to take any and all suggestions about it. I think there is a fair argument for giving Biological Crystallography its own page, but for now I'll do the edit in page. I was thinking about doing stuff under the following sub-headings

• Diffraction Theory
• Crystallisation
• Data Collection
• Phasing
  • Molecular Replacement
  • Heavy Atom Phasing
• Structure Refinement

Let me know what you think... Bassophile 20:55, 9 February 2006 (UTC)

I removed the notice about merging this article with crystallography. That article clearly discusses other techniques beside x-ray. It is not clear to me that they need to be merged. Rmhermen 21:01, Nov 14, 2003 (UTC)

Yes, crystallography addresses additional techniques, but those others are also based on diffraction from crystals and on the construction an image by fourier transformation, and so a lot of the explaining that needs doing for one of them needs doing for all of them. I think we should have one good explanation of the commonalities in one article and links to specific articles just for the fine points, such as that a lot of X-ray stuff is going on at synchrotrons and figures in big international proteomics initiatives. 168... 21:51, 14 Nov 2003 (UTC)

Not the same as merging though. I don't know that there is anything wrong with having a detailed explanation of all techniques at crystallography, and a brief explanation and fine points at each kind. Some general description needs to stay here for people who arrive directly by links to x-ray crystallography. It just isn't polite to click on a link and be immediately told to click another to get the basics and then come back. Rmhermen 14:07, Nov 15, 2003 (UTC)

Contents 1 um.. I'm doin a science essay on xray crystallography 2 Methods 3 Temperature 4 Resolution 5 UserBox 6 Article is incoherent

[edit] um.. I'm doin a science essay on xray crystallography

Can you answer these questions for me??? What is it? What is it used for? and.. What minerals are used? thank you for your time gracee***

The article itself should answer the first two questions. As far as what minerals are used, I'm not sure I understand the question.

If you're asking what minerals this type of diffraction can be used on, the answer is "basically anything". It won't work very well on obsidian, because amorphous solids don't diffract very strongly.

As far as testing the instrument itself, the only thing I've seen used is lithium fluoride, but I think graphite is also a fairly practical material to produce controlled diffraction. Honestly, though, you can use anything with a known crystalline structure, it's just that more complicated structures make the math more difficult.

As far as the minerals used to make one, a fair amount of iron and copper ore go into making the machine in general, and you need some tungsten for the X-ray tube's filament. Some parts are stainless, so that takes chromium and nickel, and there are usually some parts made of glass and some control circuitry made of silicon. Some petrolium goes into making insulators for the wiring and such, and a fair amount of fossil fuels are quite likely to be burnt at the local power station in order to run the thing.

Could you ask a more specific question?--Joel

You can determine the 3d structure of -pretty much- any molecule using x-ray crystallography. Could be small molecule or really huge molecules like proteins. All you need is crystals of that molecule really. -Ert

[edit] Methods

It would be helpful if there was a section on methods for determining structure (eg. Laue methods, Debye-Sherra method, etc.). I'm just researching it so I don't think I'd be much help atm.

[edit] Temperature

The article states that usually one works at 100K. Has it always been this way (and if so, why)? I'm reading an Acta Cryst. of 1976 and it doesn't mention the work temperature. It wold be very interesting to me to know whether I should assume that the determination was done at room temperature or at 100K... Thanks :-)

No, rt was common until cryojets were developed in the 1990's. The use of low temperature significantly improves the data due to less molecular motion and disorder.Hokietiki@hotmail.com 22:38, 29 January 2007 (UTC)

[edit] Resolution

I updated the link to resolution to Sensor resolution. This might have needed to be a link to Optical resolution. Feel free to change it if you have more insight in to this then me. --STHayden 22:21, 6 August 2006 (UTC)

[edit] UserBox

Would anyone like this:

Bassophile 13:46, 11 January 2007 (UTC)

[edit] Article is incoherent

It's not clear whether the article is about x-ray crystallography (generic field of study and family of analytical techniques) or about the analytical technique of single-crystal x-ray diffraction. It also seems that other methods such as powder diffraction are mixed up in this article. In my line of work few people would refer to powder or thin-film diffraction as "crystallography", whereas the single-crystal jocks call themselves "crystallographers". I have substantial experience in non-single-crystal methods and have started an alternative page x-ray diffraction to clear this up. Irene Ringworm 16:43, 28 February 2007 (UTC)

I agree. This page is trying to be too many things at once. Maybe splitting powder diffraction methods and single crystal methods up is the right thing to do. If we stick a disclaimer at the top, refering people interested in power diffraction methods to your page - would that be clearer??? Bassophile 09:23, 1 March 2007 (UTC)

One vote for Basophile. Plese split the diffraction and single crystal methods up. It would give the article much more focus. 130.216.191.182

I don't think an explicit disclaimer is necessary. I've cleaned up the introduction to explicitly state the scope of the article and think that should suffice. Also, my x-ray diffraction page explicitly refers people to the crystallography page in the opening section. Irene Ringworm 14:50, 1 March 2007 (UTC)

Excellent. I think that this looks much less incoherent. Not just for some time to do some more editing... Bassophile 13:05, 5 March 2007 (UTC)