Types of Centrifugal Separations

Types of Centrifugal Separations

• Differential Centrifugation: Separates particles based on size; larger particles sediment faster than smaller ones during centrifugation.

• Used for obtaining partially pure preparations of subcellular organelles and macromolecules.

• Resulting pellet contains a mixture from larger to smaller particles; supernatant consists of liquid plus most slowly sedimenting components.

• Density Gradient Centrifugation: Preferred method for purifying subcellular organelles and macromolecules by creating density gradients with multiple layers of gradient media.

Types of Centrifuge

• Microcentrifuge:

  • Designed for small volumes (0.5 - 2.0 mL).
  • Spun at speeds of 12,000–13,000 rpm.

• High-speed or Superspeed Centrifuge:

  • Handles larger sample volumes, from tens of milliliters to several liters.
  • Achieves higher speeds, around 30,000 rpm.

• Ultracentrifuge:

  • Utilizes high centrifugal forces to study biological particles.
  • Can isolate much smaller particles, including ribosomes and viruses, reaching speeds over 70,000 rpm.

• Cold Centrifuge:

  • Maintains low temperatures (-20°C to -40°C), ideal for sensitive analyses such as DNA, RNA, and proteins.
  • Achieves speeds over 30,000 rpm, with a relative centrifugal force (RCF) exceeding 65,000 x g.

Centrifuge Functionality

• A centrifuge separates particles from solutions based on size, shape, density, viscosity, and rotor speed by applying high gravitational force.
• Denser particles sink while lighter ones rise; if densities are equal, particles remain in suspension.
• Commonly used to separate macromolecules like cells, organelles, proteins, nucleic acids (DNA, RNA), and salts.

Principle of Centrifugation

• Operates on the sedimentation principle; denser substances settle at the bottom of the tube.
• In blood centrifugation, blood cells gather at the bottom, while plasma remains at the top.
• Variables impacting centrifugal force include mass, shape, speed, and radius.

Learn about differential centrifugation, a method for separating particles based on size, commonly used for obtaining partially pure preparations of subcellular organelles and macromolecules.