User:Brian P. Josey/Notebook/2009/09/01: Difference between revisions
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== | ==Notes of Papers== | ||
* Larry asked me to look at a paper, "Force production by single kinesin motors" by Schnitzer et. al. He wanted me to find how the authors derive three of the equations, 2,4 and 5. I | * Larry asked me to look at a paper, "Force production by single kinesin motors" by Schnitzer et. al. He wanted me to find how the authors derive three of the equations, 2,4 and 5. | ||
*Unfortunately I was unable to resolve this issues for him. I will return to the paper at a later date to see if I can understand it more. | |||
However we did discuss the paper that I read last week, "Mechanical Design of Translocating Motor Proteins" by W. Hwang. The paper is a review of how basic motor proteins move in the cell. The authors suggest that we currently know enough about these proteins to create what is essentially a mechanical parts list that are necessary for the proteins to move. They then go on to explain the basic mechanics of how the proteins propagate. While they discuss a wide variety of different proteins, my notes will be limited to the discussion of kinesin due to its relevance to my own work. | |||
There are a few key characteristics of the proteins that can be measured. They are: | |||
*Unloaded Velocity- The unloaded velocity is essentially the maximum speed that the protein goes when it does not encounter any obstacles or has a load. This occurs when the load is not present and there are no obsticles in the way of protein. Because there is no load, there is a minimum amount of drag, although there still is some drag from the movement relative to the surrounding medium. For Kinesin-1 the typical unloaded velocity is ~700nm/s. | |||
*Stall Force- The stall force is how much force is need to stop the motor from moving. For Kinesin-1 this typically falls in to the range of 5-7 pN. | |||
*Step Size- The step size is simply how far the protein can go in a single step, which for kinesin is 8 nm, a value that correspond to the size of a tubulin dimer. | |||
*Processivity- Processivity can be thought of as how far the motor can go along its path when unloaded. Kinesin is noted to have a higher processivity compared to other motors. The authors note that a protein that keeps its motor heads out of phase with each other in their steps is prone to have a higher processivity. Also, if proteins work as a group by forming pairs and binding to the same cargo this also increases the processivity. They do not state how this would work, but I figure that it is because one can take over for both if the other disassociates from the track, giving it time to reattach. | |||
*Efficiency- How efficient the motor is is simply the maximum amount of work that can be done divided by the change in free energy. For kinesin, with a stall force of ~6pN and a steop size of 8.2 nm the efficiency is 48-60% | |||
From here the authors continue on with a list of mechanical parts that are necessary for the protein to do its function, namely to move along a track while transporting a cargo. | |||
Pulled away, I'll finish this later (hopefully this evening) | |||
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Notes of Papers
However we did discuss the paper that I read last week, "Mechanical Design of Translocating Motor Proteins" by W. Hwang. The paper is a review of how basic motor proteins move in the cell. The authors suggest that we currently know enough about these proteins to create what is essentially a mechanical parts list that are necessary for the proteins to move. They then go on to explain the basic mechanics of how the proteins propagate. While they discuss a wide variety of different proteins, my notes will be limited to the discussion of kinesin due to its relevance to my own work. There are a few key characteristics of the proteins that can be measured. They are:
From here the authors continue on with a list of mechanical parts that are necessary for the protein to do its function, namely to move along a track while transporting a cargo. Pulled away, I'll finish this later (hopefully this evening) | |
