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Model mimics molecular travelers

Ever wonder how stuff moves around in your body? The Max Planck Institute uses models to follow particles on their intercellular travels.

Your body is a riot of traffic jams, but researchers in Germany hope to understand them better in an effort to improve health care.

Scientists at the Max Planck Institute of Colloids and Interfaces in Potsdam have created a simulation of the nano-size engines and transport systems in human bodies that move particles from one cell or region of the body to another.

Potentially, human-engineered transport systems based on principles being distilled by the simulation could be used to create faster hybrids for lab experiments or drug delivery systems.

Micrometer bead transport
Photo: Max Planck Institute of Colloids and Interfaces
Three snapshots showing the transport of a micrometer bead at 0, 4 and 8 seconds. The bead is pulled by molecular motors along parallel filaments.

These transport systems consist of two parts: filaments, which form a network of rails; and molecular motors, proteins that shuttle other particles around from one cell to another. While most of the filaments are small, some, such as those that transport organelles between nerve cells, can be more than a foot long.

The motor proteins effectively march down the filaments with two "legs" by converting chemical energy to mechanical work in an efficient manner. The proteins progress at about 1 micrometer (a millionth of a meter) per second.

"The absolute value of this velocity is not very impressive, but relative to its size, the motor molecule moves very fast: indeed, on the macroscopic scale, its movement would correspond to an athlete who runs 200 meters in one second," the Institute stated in a statement. "This is even more surprising if one realizes that the motor moves in a very viscous environment since it steadily undergoes many collisions with a large number of water molecules."

Another interesting aspect is that the proteins will hop off a rail and then hop on again later to avoid collisions with another protein.

In the simulations created by the institute, researchers found that there were fewer collisions when the filaments were organized in a radial, or spoke, fashion rather than when being built as a series of parallel tracks.