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September 22, 2006

More about Observing Molecules

A longer article that reviews the current state and development history of observing single molecules

In 1993, Block and his colleagues were the first to observe the movement of an individual molecule of kinesin, a tiny protein that carries chromosomes, neurotransmitters and other vital cargo along minute tracks called microtubules in living cells. Using a sensitive microscope-based instrument known as an optical trap, the Block team observed that kinesin moves along microtubules in discrete steps that are a mere 8 nanometers long. "Kinesin and other motor molecules are really nature's nanotechnology," he said.

By 2005, he and his colleagues had made dramatic improvements in the optical trap that enabled them to measure a single enzyme moving along a strand of DNA to within a distance of one-tenth of a nanometer, which is equivalent to the diameter of a single hydrogen atom.

"Between 1993 and 2005, the resolution improved from 8 nanometers to 3.4 angstroms," Block said. "That means we were able to make observations that are 25 times smaller in a period of about 10 years.


Block's team has a new DNA sequencing method. They measure how long a single enzyme, called RNA polymerase, pauses at each base's location.

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