AN IMPROVED AIR-DRIVEN TYPE OF ULTRACENTRIFUGE FOR MOLECULAR SEDIMENTATION.

Area of Science:

• Biophysics
• Biochemistry
• Analytical Chemistry

Background:

• Ultracentrifugation is crucial for determining molecular properties like sedimentation constants.
• Existing ultracentrifuges may have limitations in speed, stability, or operational efficiency.
• Accurate measurement of protein sedimentation requires stable, high-force centrifugal fields.

Purpose of the Study:

• To describe the construction and operational characteristics of a novel air-driven ultracentrifuge.
• To evaluate the ultracentrifuge's suitability for determining protein sedimentation constants.
• To present an improved design for high-speed vacuum ultracentrifugation.

Main Methods:

• Construction of an air-driven ultracentrifuge with a forged aluminum alloy rotor (185 mm diameter, 3,430 gm).
• Operation in a vacuum (<1 micron Hg) with a transparent cell accommodating a 15 mm fluid column.
• Achieving rotor speeds of 60,000 RPM (260,000 x g) and utilizing Svedberg's optical systems for boundary monitoring.

Main Results:

• The ultracentrifuge rotor operated at 60,000 RPM without deformation or cell leakage.
• High-speed runs showed no detectable rotor vibrations, indicated by sharp sedimentation photographs.
• Minimal rotor temperature increase (1-2°C) was observed after hours of operation at high speed under vacuum.
• No convection currents interfered with protein molecule sedimentation.
• Achieved desired speeds with moderate air pressure and rapid acceleration/deceleration.

Conclusions:

• The improved air-driven ultracentrifuge is a robust and efficient instrument for protein sedimentation analysis.
• Its stable operation at high speeds and in vacuum minimizes experimental artifacts.
• The design facilitates accurate determination of sedimentation constants for protein molecules.