Structural changes in alpha-crystallin and whole eye lens during heating, observed by low-angle X-ray diffraction.
Whole eye lens and alpha-crystallin gels and solutions were investigated using X-ray scattering techniques at temperatures ranging from 20 degrees C to 70 degrees C. In whole lens isolated in phosphate-buffered saline, the spacing of the dominant X-ray reflection seen with low-angle scattering was constant from 20 degrees C to 45 degrees C but increased at 50 degrees C from 15.2 nm to 16.5 nm. At room temperature, the small-angle X-ray diffraction pattern of the intact lens was very similar to the pattern of alpha-crystallin gels at near-physiological concentration (approximately 300 mg/ml), so it is reasonable to assume that the alpha-crystallin pattern dominates the pattern of the intact lens. Our results therefore indicate that in whole lens alpha-crystallin is capable of maintaining its structural properties over a wide range of temperature. This property would be useful in providing protection for other lens proteins super-aggregating. In the alpha-crystallin gels, a moderate increase in both the spacing and intensity of the reflection was observed from 20 degrees C to 45 degrees C, followed by an accelerated increase from 45 degrees C to 70 degrees C. Upon cooling, this effect was found to be irreversible over 11 hours. Qualitatively similar results were observed for alpha-crystallin solutions at a variety of lower concentrations.
Regini
J W
JW
The Structural Biophysics Group, School of Optometry and Vision Sciences, Cardiff University, Cardiff CF10 3NB, UK. reginijw@cardiff.ac.uk
Grossmann
J G
JG
Burgio
M R
MR
Malik
N S
NS
Koretz
J F
JF
Hodson
S A
SA
Elliott
G F
GF
D000818:Animals; D005782:Gels; D006358:Hot Temperature; D007908:Lens, Crystalline / Q000737:chemistry*; D011487:Protein Conformation; D011817:Rabbits; D012996:Solutions; D013696:Temperature; D014961:X-Ray Diffraction / Q000379:methods*; D038201:alpha-Crystallins / Q000737:chemistry*
D005782:Gels; D012996:Solutions; D038201:alpha-Crystallins