Flash-cooling and annealing of protein crystals

Flash‐cooling and annealing of macromolecular crystals have been investigated using in situ X‐ray imaging, diffraction‐peak lineshape measurements and conventional crystallographic diffraction. The dominant mechanisms by which flash‐cooling creates disorder are suggested and a fixed‐temperature anne...

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Bibliographic Details
Published in:Acta crystallographica. Section D, Biological crystallography. Biological crystallography., 2002-03, Vol.58 (3), p.459-471
Main Authors: Kriminski, S., Caylor, C. L., Nonato, M. C., Finkelstein, K. D., Thorne, R. E.
Format: Article
Language:English
Subjects:
Animals
annealing
Chickens
cryocrystallography
cryoprotection
Crystallization
Crystallography, X-Ray
flash-cooling
Models, Molecular
Muramidase - chemistry
Protein Conformation
radiation damage
Temperature
thermal expansion
Water
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Summary:Flash‐cooling and annealing of macromolecular crystals have been investigated using in situ X‐ray imaging, diffraction‐peak lineshape measurements and conventional crystallographic diffraction. The dominant mechanisms by which flash‐cooling creates disorder are suggested and a fixed‐temperature annealing protocol for reducing this disorder is demonstrated that should be more reliable and flexible than existing protocols. Flash‐cooling tetragonal lysozyme crystals degrades diffraction resolution and broadens the distributions of lattice orientations (mosaicity) and lattice spacings. The diffraction resolution strongly correlates with the width of the lattice‐spacing distribution. Annealing at fixed temperatures of 253 and 233 K consistently reduces the lattice‐spacing spread and improves the resolution for annealing times up to ∼30 s. X‐ray images show that this improvement arises from the formation of well ordered domains with characteristic sizes >10 µm and narrower mosaicities than the crystal as a whole. Flash‐cooled triclinic crystals of lysozyme, which have a smaller water content than the tetragonal form, diffract to higher resolution with smaller mosaicities and exhibit pronounced ordered domain structure even before annealing. It is suggested that differential thermal expansion of the protein lattice and solvent may be the primary cause of flash‐cooling‐induced disorder. Mechanisms by which annealing at T
ISSN:1399-0047
0907-4449
1399-0047
DOI:10.1107/S0907444902000112