Changes in the X-ray diffraction pattern from lens during a solid-to-liquid phase transition.
OBJECTIVE
The purpose of this study is to compare the structural integrity of bovine lenses using small-angle X-ray diffraction techniques, before and after freezing, using both liquid nitrogen and a -20 degrees C freezer to understand the molecular changes that occur and to see if any permanent structural changes result from the freezing and thawing process.


METHODS
We used small-angle X-ray scattering to investigate the effects of freezing whole bovine eye lenses (i) in liquid nitrogen and (ii) at -20 degrees C, to better understand the structural basis of the phase transitions.


RESULTS
Lenses frozen in liquid nitrogen thawed more rapidly than those placed at -20 degrees C. With both freezing methods, X-ray patterns taken during the thawing process indicated less protein order than before or after freezing. After both freezing methods, the X-ray reflection returned to its original spacing and close to its original intensity values before freezing.


CONCLUSIONS
We explain these phenomena in terms of a simple model based on the melting of ice crystals. We also suggest that the liquid nitrogen method of freezing is probably the better method of cryo-preservation for maintaining lens crystallin order.
Regini
Justyn W
JW
The Structural Biophysics Group, School of Optometry and Vision Sciences, Cardiff University, Cardiff, CF24 4LU, UK. reginijw@cf.ac.uk
Meek
Keith M
KM
D000818:Animals; D001834:Body Water / Q000737:chemistry*; D002417:Cattle; D015925:Cryopreservation / Q000379:methods; D003459:Crystallins / Q000737:chemistry*; D007908:Lens, Crystalline / Q000737:chemistry*; D044367:Phase Transition; D014961:X-Ray Diffraction
D003459:Crystallins