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X-ray diffraction study of the live squid retina
1Department of Biophysical Engineering, Faculty of Engineering Science, Osaka University, Japan.
Journal of Molecular Biology
|April 29, 1994
Summary
Synchrotron X-ray diffraction reveals the hexagonal structure of unfixed squid microvilli. This method overcomes fixation artifacts, showing a large inter-microvillar space crucial for understanding membrane potential.
Area of Science:
- Structural biology
- Neuroscience
- Biophysics
Background:
- Invertebrate rhabdomes are labile and require fixation for X-ray diffraction.
- Conventional X-ray methods need long exposure times (over 10 hours).
- Previous fixation methods may introduce artifacts, obscuring structural details.
Purpose of the Study:
- To obtain X-ray diffraction patterns from unfixed squid retina.
- To determine the precise structure of microvilli using advanced X-ray techniques.
- To investigate potential artifacts introduced by chemical fixation.
Main Methods:
- Utilized synchrotron radiation for high-intensity X-rays.
- Employed a storage phosphor screen as a detector for rapid data acquisition.
- Analyzed X-ray diffraction data using Patterson function analysis and model building.
Main Results:
- Successfully obtained diffraction patterns from unfixed squid retina.
- Indexed diffraction spots on a 2D hexagonal lattice (60 nm).
- Revealed hexagonal microvillar cross-sections and a significant inter-microvillar gap (approx. 12 nm).
- Confirmed the presence of substantial inter-microvillar material.
Conclusions:
- Synchrotron radiation enables structural analysis of labile tissues without fixation.
- The observed inter-microvillar space is larger than previously seen, potentially explaining ionic current flow.
- Fixation artifacts may have masked crucial structural features in prior studies.