X-ray diffraction patterns from microtubules and neurofilaments in axoplasm

Area of Science:

• Biophysics
• Cell Biology
• Structural Biology

Background:

• Axoplasm from Myxicola infundibulum and Loligo contains oriented cytoskeletal elements.
• X-ray diffraction allows examination of native axoplasmic structures and interactions.

Purpose of the Study:

• Analyze X-ray diffraction patterns from Myxicola and Loligo axoplasmic fibers.
• Investigate the structural basis of X-ray diffraction patterns from microtubules and neurofilaments.
• Determine the effect of hydration on axoplasmic fiber X-ray diffraction.

Main Methods:

• Extraction and fiber formation of axoplasm from Myxicola infundibulum and Loligo.
• X-ray diffraction analysis of native and hydrated axoplasmic fibers.
• Comparison of experimental X-ray patterns with Fourier transforms from electron microscopy.

Main Results:

• Myxicola axoplasmic fibers showed X-ray diffraction patterns attributed to neurofilaments and microtubules.
• Loligo axoplasmic fibers showed patterns solely from microtubules.
• Hydration caused reversible changes in X-ray pattern intensities, notably on the 4 nm layer-line (J3 reflection) and J10/J16 reflections, without altering layer-line positions.
• Hydrated fiber X-ray patterns resembled those of purified microtubules, with central wall contrast.

Conclusions:

• X-ray diffraction is effective for studying native axoplasmic cytoskeletal components.
• Microtubule structure contributes significantly to axoplasmic X-ray diffraction patterns.
• Hydration induces reversible structural changes in axoplasmic fibers, impacting X-ray diffraction intensities and providing insights into microtubule wall structure.