centrifugation Flashcards
what is a centrifuge used for?
separation of particles or microorganisms from the suspended fluid using centrifugal force
what is another name for centrifugal force?
g-force
particles separate according to what?
size
shape
viscosity of medium
rotor speed
density
when can centrifugation only be used?
only when the dispersed material is denser than the medium
true or false: higher density particles sediment in influence of gravitational field
true
what is the movement under gravitational force called?
sedimentation
true or false: when the centrifugal force is applied by the centrifuge, the particles move slower
false, they move faster
relative centrifugal force is expressed as?
a multiple of the acceleration (G) due to gravity (g)
what kind of force does a sample experience in a centrifuge?
centrifugal force
what is the rate of sedimentation dependent on?
the centrifugal field
what is the applied centrifugal force determined by?
the radial distance of the particle from the axis of rotation
how is centrifugal field generally expressed?
in multiples of gravitational speed (9.8m/s^2)
RCF is the ratio of what?
ratio of centrifugal acceleration (G) and gravitational acceleration (g)
what is the formula for RCF?
RCF = 1.12 x 10^-5 (RPM)^2 (r)
what are the 2 types of centrifuge rotors?
fixed angle and swinging bucket
what is a fixed angle rotor?
particles only have a short distance to travel before pelleting
shorter run time
widely used
what is a swinging bucket rotor?
longer distance of travel for better separation such as in density gradient centrifugation
easier to withdraw supernatant without disturbing the pellets
high speed centrifuges can handle what kind of samples?
larger sample volumes
how much rpm can larger centrifuges reach?
high rpm, 30000rpm or 15,000-20,000rpm
what kind of sample containers can large high speed centrifuges hold?
various test tubes
bottles
microliter plates
where are ultracentrifuges used?
studies of membrane fractionation
how much rpm can ultracentrifuges reach?
70,000rpm or 65,000rpm
how does an ultracentrifuge work?
it can separate molecules in batch or continuous flow systems
during the run, particles will migrate through the test tube at different speed depending on their physical properties and properties of the solution
high speed or ultracentrifuge: large sample capacity
high speed
high speed or ultracentrifuge: normally refrigerated
high speed
high speed or ultracentrifuge: expensive
ultra
high speed or ultracentrifuge: research applications
both
high speed or ultracentrifuge: limited lifetime
ultra
high speed or ultracentrifuge: 15,000-20,000rpm
high speed
high speed or ultracentrifuge: need special rotors
ultra
high speed or ultracentrifuge: care in use, balance is critical
ultra
high speed or ultracentrifuge: 65,000rpm (100,000’s x g)
ultra
where are microcentrifuges used?
process small volumes of biological molecules, cells, or nuclei
how much liquid does a microcentrifuge hold?
0.5-2mL
what is the angular speed of a microcentrifuge?
12,000-13,000rpm
true or false: microcentrifuges can fit on a table top and have rotors that can change speed quickly
true
true or false: microcentrifuges should always be refrigerated
false, they can or cannot be
what type of centrifuge is used to separate erythrocytes, blood samples, coarse precipitates, and cells
small bench centrifuge
what is the speed and RCF of a small bench centri?
speed 4,000-6,000 rpm
RCF 3,000-7,000g
at what speed and RCF are small samples sedimented?
speed 8,000-13,000rpm
RCF 10,000g
how long does a small bench centri sediment a small volume
1-2mins
small bench top or microcentrifuge: common in biochem/molbio/bio labs
micro
small bench top or microcentrifuge: can take up to 100 test tubes depending on diameter
small bench
small bench top or microcentrifuge: can take force up to 15,000g
micro
small bench top or microcentrifuge: with or without refrigeration
both
small bench top or microcentrifuge: common in clinical labs (blood/plasma/serum separation)
small bench
ssmall bench top or microcentrifuge: slow speed
small bench
small bench top or microcentrifuge: can take small volumes up to 2mL
micro
kind of gradient media: preserves morphology and activity of subcellular fractions
sucrose and ficoll
kind of gradient media: isopycnic density gradient technique
cesium chloride
potassium bromide
kind of gradient media: bec of low osmolarity, low viscosity and large particle size, it is suitable for cell separation, bacteria viruses, and subcellular organelles
percoll
kind of gradient media: isolation of membrane fractions via floatation
metrizamide
nycodenz
kind of gradient media: cell fractionation
renografin
required centrifugal force of nuclei
800-1,000g
required centrifugal force of mitochondria, chloroplasts, microbodies
20,000-30,000g
required centrifugal force of RER membranes
50,000-80,000g
required centrifugal force of plasma membranes, SER
80,000-100,000g
required centrifugal force of free ribosome particles
150,000-300,000g
what is the material of most rotors?
aluminum or titanium
true or false: aluminum rotors are corrosion resistant, while titanium is not
false, titanium is corrosion resistant and aluminum is not
what are the applications of centri in biological sciences?
separate cellular and subcellular components
separate one cell form another
removing cells from suspended liquid
isolating viruses and macromolecules
study effects of centri force on cells, embryos, protozoa
determine certain properties abt cells
