Soft Nanomaterials

Question 1

Hard technology

Answer 1

• rigid bars transmitting forces directly
• high precision
• high vacuum operation
• molecular motion a problem to be overcome

Question 2

Soft technology

Answer 2

• floppy systems
• fault tolerant
• water universally present
• molecular motion and opportunity to be used

Question 3

Random motion of molecular motors

Answer 3

• a protein with a number of possible shapes can move around on a rod since each shape will have a different interaction
• brownish motion will unstick the molecule, allowing it to explore the rod randomly
• directed motion must be achieved using free energy
• this is usually provided by ADP/ATP reaction

Question 4

Directed motion continued

Answer 4

• molecule has binding site
• ATP binds, changing molecular shape, molecule shifts on rod
• bound ATP hydrolyses to ADP and phosphate ion, releasing energy and changing shape
• release of ADP and phosphate ion returns molecule to start
• release of energy means ATP-ADP step is irreversible

Question 5

The actin protein

Answer 5

• most abundant protein in eukaryotic cels
• exists as globular (G) and linear polymer microfilament (F)
• controls cell motion, shape, muscle action through interaction with myosin
• F provides internal scaffolding for mechanical support and cell motion must

Question 6

Myosin

Answer 6

• Catalytic core binds weakly to actin - each head acts independently and attaches one at a time
• if calcium conc high, ATP is hydrolysed to ADP and phosphate - head binds to actin
• when actin docks phosphate is released from the active site, lever arm swings to poststroke, ADP bound state, and actin filaments is moved by 100um
• after stroke ADP dissociates and ATP binds to active site, rapidly reverting catalytic core to weak-binding actin state, lever arm recocks back to prestroke state