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Proteoglycans contain a 4.6 A repeat in muscular dystrophy corneas: x-ray diffraction evidence
A J Quantock1, G K Klintworth, D J Schanzlin
1Anheuser-Busch Eye Institute, Department of Ophthalmology, St. Louis University School of Medicine, Missouri 63104, USA. quantoaj@sluvca.slu.edu
Biophysical Journal
|April 1, 1996
Summary
Macular corneal dystrophy (MCD) corneas exhibit a unique 4.6 A x-ray reflection due to specific ultrastructures. This reflection, linked to glycosaminoglycans and proteoglycans, is diminished by glycosidase treatment, revealing insights into MCD corneal structure.
Area of Science:
- Ophthalmology
- Biophysics
- Materials Science
Background:
- Macular corneal dystrophy (MCD) is characterized by an unusual ultrastructure in corneas.
- Synchrotron X-ray diffraction reveals a distinct 4.6 Å reflection in MCD corneas, absent in normal corneas.
Purpose of the Study:
- To investigate the origin of the 4.6 Å reflection observed in macular corneal dystrophy (MCD) corneas.
- To elucidate the role of specific molecular components in the MCD corneal ultrastructure.
Main Methods:
- Wide-angle X-ray diffraction patterns were compared between normal and MCD human corneas.
- MCD corneal tissues were treated with specific glycosidases (chondroitinase ABC, N-glycanase) prior to X-ray diffraction analysis.
Main Results:
- All four MCD corneas displayed a 4.6 Å X-ray reflection (MCD type I at 4.65 Å and 4.63 Å; MCD type II at 4.63 Å and 4.67 Å), while normal corneas did not.
- The 4.6 Å reflection intensity was reduced after enzymatic treatment with chondroitinase ABC or N-glycanase.
Conclusions:
- Glycosaminoglycans or proteoglycans are implicated in the 4.6 Å X-ray reflection of MCD corneas, suggesting a periodic ultrastructure.
- The findings suggest the 4.6 Å ultrastructure in MCD corneas may involve intact, unsulfated lumican molecules, CS/DS-containing molecules, or a hybrid macromolecular aggregate.