BERKELEY, CA -- Thanks to the film, Jurassic Park, and news coverage of the O.J. Simpson trial, the whole world now knows that PCR -- the polymerase chain reaction -- is the method by which scientists replicate millions of copies of a DNA fragment for use in research or forensic analysis. Long before either event, scientists at the Ernest Orlando Lawrence Berkeley National Laboratory (LBNL) were using PCR to help in the painstaking task of mapping and sequencing the three billion letters of the human genetic code.
Now, engineers in the instrumentation group at LBNL's Human Genome Center, working closely with their biologist colleagues, have developed an improved type of apparatus, called a "rapid thermal cycler," that can perform the required PCR steps in less than half the time. A next generation rapid thermal cycler, in its final stages of development, will be even faster and could lead to a total robotic automation of the PCR process.
The PCR technique, which was invented in 1985 by Nobel Laureate Kary Mullis, involves three basic steps, each of which must be performed at a specific temperature. To be most effective, these temperature changes should be as rapid as possible. In conventional PCR equipment, an array of tubes or vials holding samples of DNA is placed in a metal block, and the temperature of the samples is controlled by heating and cooling the block.
In the Berkeley Lab's rapid thermal cycler, the samples are placed in wells in a plastic plate and water circulating under the plate sets the temperature of the samples. To change the temperature, water flow is merely switched from one tank to another. This results in faster temperature changes, more samples processed per hour, and an improved signal-to-noise ratio in the data. The design of the rapid thermal cycler also reduces sample preparation and handling procedures by about 40 minutes per array.
The prototype model of the rapid thermal cycler was designed by engineer Tony Hansen. The improved version, now in its final stage of development, was designed by engineer Kanchi Karunaratni. Both have worked closely with Chris Martin, a biologist and one of the principal investigators with the Human Genome Center. In the new version, the heating and cooling process is controlled by a sophisticated computer system similar to the controller systems that run automated factory assembly lines. The result is speedier and more precise temperature regulation. The new version is also more energy efficient, provides four work stations rather than three, and is about a third smaller than the original (a plus in crowded biology laboratories).
In addition to Hansen, Karunaratni, and Martin, other Berkeley Lab researchers involved in the design of the rapid thermal cycler include Dave Wilson, Davey Hudson, Charlie Reiter, and Don Uber (software). Joe Jaklevic heads the Human Genome Center's instrumentation group.
The Ernest Orlando Lawrence Berkeley National Laboratory is a U.S. Department of Energy national laboratory located in Berkeley, California. It conducts unclassified scientific research and is managed by the University of California.