X-ray diffraction of myelin membrane. I. Optimal conditions for obtaining unmodified small angle diffraction data...

Area of Science:

• Biophysics
• Neuroscience
• Structural Biology

Background:

• Myelin sheath structure is crucial for nerve impulse conduction.
• Understanding myelin's electron density distribution provides insights into its function.

Purpose of the Study:

• To investigate the electron density distribution of frog sciatic nerve myelin.
• To determine the structural basis of myelin's X-ray diffraction pattern.

Main Methods:

• X-ray diffraction using a Kratky small angle slit camera.
• Analysis of diffraction patterns to obtain electron density distribution.
• Examination of disorder by comparing crystallite size and diffraction peak width.

Main Results:

• A fundamental repeat distance of 171 +/- 2.8 A was observed.
• The number of reflections did not increase with varied experimental conditions.
• The limited diffraction spectra were not due to disorder.

Conclusions:

• The myelin membrane's electron density distribution is not characterized by sharp steps.
• The distribution approximates a modified cosine function.
• This distribution is the cause of the observed X-ray diffraction pattern.