BioMedical Instrumentation-II What is centrifugation? Basic principle of centrifugation Interacting Forces
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This document provides an overview of centrifugation as a method to separate particles in a solution. It discusses the basic principles, including that centrifugation uses centrifugal force to accelerate the sedimentation of particles based on properties like density, size, and shape. It separates components faster than simple gravitational sedimentation. The document also outlines the interacting forces involved, such as buoyant force and frictional force, and provides examples of calculating centrifugal force and field.
BioMedical Instrumentation-II What is centrifugation? Basic principle of centrifugation Interacting Forces
- 1. Lecture no : 1 BioMedical Instrumentation-II Mr. Muhammad Moazzam Lecturer(Biomedical Department) University of the Lahore
- 2. Contents • What is centrifugation? • Basic principle of centrifugation • Interacting Forces
- 3. Centrifugation Method Centrifugation method is a process of separating different components or the suspended particles from the homogenous solution, by the practice of centrifugal force. It separates particles based on their physical properties like size, shape, density etc. and chemical properties like molecular weight and viscosity.
- 4. Centrifugation Method A natural gravitational force can also concentrate particles but in an indefinite time so to increase its efficiency, a centrifugal force function to separate particles by their sedimentation property. The rate of sedimentation increases and decreases as per the increase in gravitational force and viscosity of the medium respectively.
- 5. History •The first analytical ultracentrifuge was developed by Svedberg in 1920
- 6. What is centrifugation? • A technique used to accelerate the sedimentation process by applying centrifugal force • Different types of centrifugation techniques are used to separate suspended particles from a liquid in which the particles are not soluble • Liquids of different densities may also be separated • Applications of centrifugation: separation of serum or plasma from RBCs, sedimentation of cells and viruses, separation of subcellular organelles, and isolation of macromolecules such as DNA, RNA, proteins, or lipids
- 7. Basic principle of centrifugation • A centrifuge uses centrifugal force (g-force) to isolate suspended particles from their surrounding medium • When a suspension is rotated at a certain speed or revolutions per minute (RPM), centrifugal force causes the particles to move radially away from the axis of rotation • The force on the particles (compared to gravity) is called Relative Centrifugal Force (RCF)
- 8. BASIC PRINCIPLES OF SEDIMENTATION • When designing a centrifugation protocol, it is important to keep in mind that: – the denser a biological structure is, the faster it sediments in a centrifugal field, – The more massive a biological particle is, the faster it moves in a centrifugal field, – the denser the biological buffer system is, the slower the particle will move in a centrifugal field,
- 9. BASIC PRINCIPLES OF SEDIMENTATION • The greater the frictional coefficient is, the slower a particle will move • The greater the centrifugal force is, the faster the particle sediments • The sedimentation rate of a given particle will be zero when the density of the particle and the medium are equal
- 10. Which factors have an influence on centrifugation : •Density of both samples and solution •Temperature/viscosity •Distance of particles displacement •Rotation speed
- 11. Types of centrifugation Based on the type of separation molecules, there are two significant types of centrifugation: •Preparative centrifugation: It is a technique concentrating one component from the other. •Analytical centrifugation: It is a method that measures physical, chemical and hydrodynamic properties of suspended molecules.
- 12. Principle of Centrifugation Method •A centrifugation method depends on the gravitational movement of suspended particles, which cause deposition of high- density particles towards the bottom. • It is important to note that higher is the difference between the densities of particles, easy will be the separation. If the density difference is low, then the separation becomes tough, and in such case, gravitational force must be accelerated.
- 13. Principle of Centrifugation Method •Therefore, a centrifuge accelerates the rate of sedimentation by increasing the relative centrifugal force (RCF) measures by the rotations per minute (rpm). If RCF is equal to 100X g, then it is equivalent to the centrifugal force that is a hundred times greater than the force of gravity.
- 14. Centrifugal field •A centrifugal force is a kind of force that causes circular motion of the particles and can express as: Centrifugal force(CF) = ω2r •Where, ω= Angular velocity in radians per second r= Radius of a particle from the axis of rotation ω2r= Centrifugal acceleration
- 15. Example •What is the applied centrifugal field at a point equivalent to 5 cm from the centre of rotation and an angular velocity of 3000 rad/s?
- 16. Solution •The centrifugal field, G, at a point 5 cm from the Centre of rotation may be calculated using the equation •Centrifugal force(CF) = ω2r =(3000)2x5 cm/s2 =4.5x107 cm/s2
- 17. Centrifugal field • In terms of gravitation force, the equation will represent as, • Gravitational force (G)= mg • Where g= Gravitational constant
- 18. Interacting Forces •Other than, centrifugal force, there are some other interacting forces, namely buoyant and frictional force.
- 19. Buoyant force Buoyant force •A force with which the particles must displace the liquid media into which they sediment. The opposing buoyant force is smaller for a dense particle and can express as: Buoyant force (Fb)= ρgV •Where ρ= Fluid density g= Gravitational or centrifugal acceleration V= Volume of fluid displaced
- 20. Frictional force Frictional force •A force generated by the particles as they migrate through the solution. • Frictional force (Ff )= fv •Where f= Frictional coefficient v= Sedimentation velocity
- 21. Questions?