Richard Sear University of Surrey
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Transcript of Richard Sear University of Surrey
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Richard Sear
University of Surrey
Phase Transitions: From the Big Bang to Biology
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Phase Transitions:
Around us.
In general.
In the universe.
In biology.
Plan
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Around us: Water
Water vapour transformed to liquid water.
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Phase transitions
are universal
Annual rainfall (mm)
New Haven
London
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Phase Transitions:
Symmetry
Crystals are not isotropic – here the snowflake (ice) has hexagonal symmetry
On freezing the isotropic symmetry of the liquid has been broken. Ice is less symmetric than water.
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Phase Transitions:
Sudden
Phase transitions are sudden, dramatic, phenomena
On heating water, nothing happens until suddenly at 100 C it boils.
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Phase Transitions:
Collective phenomena
One, or a few, molecules:
No phase transition.
A single molecule cannot boil, cannot freeze.
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Phase Transitions:
Collective phenomena
Only with many molecules can water and ice exist.
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The exception that
proves the rule
pdf for speed of Na atoms
Almost all phase transitions are driven by interactions between the molecules, quarks, etc.
The exception is Bose-Einstein condensation.
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Quark-hadron transition from fluid of unconfined quarks and gluons to one where they are bound in hadrons.
Image from QCD conference in Adelaide – Wilton can explain?
Phase Transitions:
In the Early Universe
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Universe expands and cools
10 μs
Phase Transitions:
In the Early Universe
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Phase Transitions:
In Biology
Fluorescent image of cells – nuclei are blue.
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A protein called
Dishevelled
Dictionary definition:
Dishevelled, adjective(of people or their appearance) very untidy
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When Dvl is mutated cells can’t polarise – so hairs point randomly
Close up of part of wing of fruit fly (Axelrod)
Normally hairs point away from body
A protein called
Dishevelled
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The protein dishevelled (Dvl) is essential for development in all animals.
A protein called
Dishevelled
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A Phase Transition
in a cell
Nucleus Cytoplasm
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A Phase Transition
in a cell
Dvl is NOT uniformly distributed in the cytoplasm of the cells.
It forms dynamic aggregates, called puncta.
Scale bar 15μm
Dale lab, JCS 2005
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Defending against
HIV attack
The protein TRIM5α (green) & microtubules (red)
TRIM5α also forms dynamic aggregates. These defend the cell against HIV.
Hope & Stoye labs
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Defending against
HIV attack
Movie
Hope & Stoye labs
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Defending against
HIV attack
TRIM13 (green) & nucleus (red)
Ballabio lab
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Measure of biological function
Bienz lab
No phase separation – no function
mutant
A Phase Transition
in a cellmutantnormal
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Interactions
engineered
Molecular interactions set by laws of physics
Protein interactions optimised by evolution
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Interactions
engineered
Molecular interactions set by laws of physics
Protein interactions optimised by evolution
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In cells phase transitions
Perform a function
Melting of ice, formation of baryons just are – consequence of laws of physics
In biology they perform a function – consequence of evolution
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Phase Transitions:
Symmetry
Water droplet in 0g (NASA)
Liquids are isotropic – droplets spherically symmetric
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The cytoplasm is crowded
David Goodsell
30 to 40 % by volume protein and RNA