The temperature most often associated with human life is 98.6 degrees Fahrenheit, that of a healthy person. Now scientists have succeeded in taking a different measurement, one they've dubbed the "heat of life:" the energies involved in DNA replication and synthesis.

Kenneth J. Breslauer of Rutgers University and his colleagues used an ultrasensitive calorimeter to measure the miniscule reaction heats associated with DNA synthesis in Escherichia coli. The team isolated a specific section of DNA and labeled parts with radioactive markers. The thermal detection system, which is accurate to a millionth of a calorie, determined the amount of heat given off when a base pair was inserted into the DNA strand. According to the report, which is published online this week by the Proceedings of the National Academy of Sciences, the amount of energy involved depends on which base pair is inserted into the strand. "Our measurements represent the first direct determination of the energies and their transformations in this most fundamental process in biological chemistry," Breslauer says.

The researchers note that their findings are a first step toward assembling a database of the energies involved in proper DNA construction. Knowing the quantities to expect could help scientists identify incorrect synthesis, which can lead to mutations and illness. "This knowledge can position us to begin to intervene, enabling us to halt incorrect synthesis though the introduction of highly targeted external agents," Breslauer explains. "It is a foundation that is a necessary, but not sufficient, step in the direction of being able to understand and to regulate DNA synthesis, not only in the lab, but in living organisms."