Cryocrystallography is the collection of crystallographic data at cryogenic temperatures primarily with the use of liquid nitrogen. The following advantages and disadvantages are comparing cryogenic vs. room temperature data collection.
Advantages
1) Reduced Radiation Damage: when compared to room temperature collection
2) Fewer Crystals: as to be expected if the radiation damage is reduced the crystal lifetime is increased therefore reducing number of crystals
3) Better Data: increased resolution, I/sigma, redundancy, reduced B values and stronger anomalous signal
4) Better Crystals: protein crystals can be selected at opportune times during the crystallization process (possibly avoid dissolving or cracking) as well as be easily transported within cryogenic dewars
Disadvantages
1) Icing: even if icing occurs it may be possible to salvage the collection during data processing
2) Cryoprotectants: many protein crystals require the use of a cryoprotectant (the most popular is the use of 20-25 % glycerol) prior to being exposed to the cold stream
3) Increased mosaicity: this can be reduced with the proper cryoprotectant as well as mounting technique (ref pg. 32)
4) Non-isomorphism: unit cell size may vary (ref)
5) Cost of equipment: include in grant applications or have at least two bake sales
In true end of the year originality here are 10 favorites from 2009:
1) Best Online Introductions to Crystallography
2) Scientific Research in 10 Simple Rules
3) Free Crystallographic Space Group Diagrams and Symbols
4) Ultimate List of Protein Crystallization Resources
5) Scientific Presentation Resources
6) 17 Structural Journals with RSS
7) Ultimate List on Cryocrystallography & Radiation Damage
Covering your Tracks
9) 10 Ways to Comfort a Crystallographer
10) Top 5 Lies of Principle Investigators
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Posted by
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Crystallographic Data Refinement,
Protein Crystallization,
Protein Expression and Purification,
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Cryocrystallography,
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Fred points us to an eighteen minute introductory video on structural biology, but unfortunately the English version is not uploaded onto a video hosting site (the French version is here for my friend Julie). I lack the rights to the video so can’t post the English version myself.
I would recommend this video to any relatives that glaze over when you describe your job or perhaps to new graduate students. Enjoy.
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Posted by
Sean |
Categories:
Crystallographic Data Collection,
Crystallographic Data Processing,
Crystallographic Data Refinement,
Protein Crystallization,
Protein Expression and Purification,
Scientific Publication and Presentation | Tagged:
Cryocrystallography,
Crystallographic Data Processing,
Crystallographic Data Refinement,
Data Collection,
Diffraction Images,
Learning,
Macromolecular Crystallography,
Merging,
Movie,
Protein Crystallization |
We traveled to the Advanced Photon Source this past weekend and rocked out on beamline 21 for 24 hours. The beamline had robotics for crystal mounting and although we did not use them for auto-mounting it was neat to see the set up. If you are interested in robotic mounting at a synchrotron near you then this page is worth exploring.
I picked a couple of bits of information about the robotics on this particular beamline.
1) Robots do not work well with certain pins. Although the 18 mm Hampton-style pin is recommended as the universal standard you need to be sure you select the right one. The Hampton Copper Magnetic HT was not allowed while the Hampton Copper Magnetic ALS HT was fine. The reason was due to the ‘upper lip’ that is present which differs between these two pins. ‘Upper lip’ meaning the ledge that is present before the pin tapers to meet the vertical copper pin. A picture can of these pins can be seen here (view full size – the left pin is not allowed while the center pin is fine). Molecular dimensions also has caps and pins that can be used.
2) Hampton caps (the plastic part that fits over the pin) were not allowed and instead had to use caps by Molecular Dimensions. The reason was being due to the consistency of length in Molecular Dimension caps. Personally, I have never noticed a difference in the lengths of the caps from Hampton.
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The crystal sits on a pin which is in a puck. The puck is placed in a container filled with liquid nitrogen. The robotic arm removes the pins from the puck, which is located inside the large container on the right side of the above picture.
I really enjoy reading and hearing stories about crystallography. A brief history of crystal mounting leading up to robotics is wonderfully covered in a paper (pdf) by Cele Abad-Zapataro.
Stephen also wrote a great post discussing his exciting times at a synchrotron awhile back.
I had the opportunity to see these dewars by Spearlab at the 2007 American Crystallography Association meeting in Salt Lake City.
They have become quite popular, but for those that have missed them they are WAY better than Glass Dewars. Foam dewars are virtually indestructible compared to Glass Dewars and run about half the price.
The dewars are also being used in ways that I would have never expected such as a transfer vessels of liquid nitrogen. Spearlab also just came out with a new 1400 mL dewar, which is shaped like the purple dewars shown above.
(couple of chapters)