Subcellular Self-Assembly Spontaneous Building of Complex Structures

Mitosis in sand dollar blastula

What was involved in the self- assembly of the microtubule? GTP Tube formation Tubulin Growing and shrinking Peeling and curving Change in shape

Brainstorm! There exists a plethora of self- assembly examples in biology

100 nm Self-assembly is critical at the nano-scale

Modeling self-assembly Arrange the marbles. Agitate gently. Observe the pattern.

What structure formed for you? Why did the marbles stick together? How did they “know” how to stick together to form a circle?

Why did the marbles stick together? Self-assembly requires a template.

Was the attraction strong or weak? The bonds holding the structure together must be fairly weak.

What drove the marbles together? Self-assembly must have an energy source.

Requires a template. Must have an energy source. The bonds holding the structure together must be fairly weak. Self-assembly has rules

Make your own template Generate this structure Use magnets Design before you build. Shake the pieces to assemble the structure.

What rules of self-assembly were incorporated into your model? Was there a template? Were the bonds fairly weak? Was there an energy source?

Viruses demonstrate self-assembly

You may be familiar with the bacteriophage

Viruses differ from bacteriophages.

Let’s look at some of the parts of self-assembly Station A –Shake the capsomers to completely assemble the capsid. –Disassemble the capsid with a quick shake of the jar. Station B –View a drop of India ink under low power. –Observe under high power. –Move low power back into place.

What’s the connection between what you observed at the two stations? Brownian MotionShaking

What was the template for the capsid? Design a template for assembly of a viral capsid. Assemble the capsid. Remember, only sides with opposite charges can be connected. + -

How did you do?

Virus capsids are based upon simple geometric designs Where is the template stored? Each kind of capsid part needs its own gene. Fewer different kinds of parts = less DNA needed!

Virus capsid assembly

These models were based on corannulene components

---C - N H ---C - O O = C ---- H H -- ++ ++ ++ Hydrogen bonds hold them together.

Can you figure out how to put them together?

Viruses are subcellular structures that self-assemble Brownian motion provides the energy. Hydrogen bonds are easy to make and easy to break. DNA provides the template for the proteins capsomers.