Changes in the X-Ray Diffraction Pattern from Lens during a Solid-to-Liquid Phase Transition

• Published in: Current eye research 2009-01, Vol.34 (6), p.492-500
• Main Authors: Regini, Justyn W., Meek, Keith M.
• Format: Article
• Language: English
• Subjects: Animals; Body Water - chemistry; Cattle; Cryopreservation - methods; crystallin proteins; Crystallins - chemistry; freezing and short-range order; ice crystals; lens; Lens, Crystalline - chemistry; Phase Transition; X-ray; X-Ray Diffraction
• ISSN: 0271-3683; 1460-2202
• DOI: 10.1080/02713680902919540

Purpose: 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°C freezer to understand the molecular changes that occur and to see if any permanent structural changes result from the freezing and thawing process. Materials and 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°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°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.