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Synchrotron x-ray diffraction studies of the cornea, with implications for stromal hydration
K M Meek1, N J Fullwood, P H Cooke
1Biophysics Group, Open University Oxford Research Unit, Boars Hill, United Kingdom.
Biophysical Journal
|August 1, 1991
Summary
Collagen spacing in bovine corneas changes with hydration. Initial water equally hydrates within and between fibrils, while later water preferentially fills interfibrillar spaces, suggesting a second fibril population.
Area of Science:
- Biophysics
- Materials Science
- Ocular Biomechanics
Background:
- Collagen fibrils form the corneal stroma, providing structural integrity.
- Understanding collagen's response to hydration is crucial for corneal biomechanics and disease research.
Purpose of the Study:
- To quantify collagen intermolecular and interfibrillar spacings in bovine corneas across varying hydration levels.
- To elucidate the distribution of water within the corneal stroma.
Main Methods:
- X-ray diffraction (low- and high-angle) using synchrotron radiation.
- Measurement of collagen spacings as a function of hydration (H).
Main Results:
- Interfibrillar spacing increased from 34 nm (dry) to 76 nm at H=5.
- Intermolecular Bragg spacing increased from 1.15 nm (dry) to ~1.60 nm at normal hydration (H~3.2).
- Initial water uptake (H=0 to H=1) affected both spacings equally, suggesting intra- and interfibrillar hydration; above H=1, water preferentially hydrated interfibrillar spaces.
Conclusions:
- Corneal collagen hydration is non-uniform, with water preferentially entering interfibrillar spaces above H=1.
- A second, less organized population of collagen fibrils may exist, contributing to non-uniform hydration.
- Findings suggest a more complex water compartmentalization within the corneal stroma than previously assumed.