Korean researcher solves 60-year-old puzzle of biological clock through math

A Korean mathematician has solved a 60-year-old puzzle in the biology community. Prof. Kim Jae-kyung of the mathematical science at KAIST said on Monday that his team solved principle in which biological clock operates properly in spite of temperature changes by using a mathematical model. It is noteworthy that the team has solved mystery of life through mathematics.

Biological clock serves to maintain 24 hour-cycle biorhythm, including the function that excretes the sleep hormone ‘melatonin’ at around 9 p.m. to cause one to fall asleep and wakes him or her around 7 a.m. However, in general biochemical reactions, a hike in temperature increases the speed of reaction. It means when the body has fever or during hot summer season, the duration of sleep could decrease. Fortunately, the human’s biological clock is maintained constantly irrespective of temperature variations. Such nature was discovered in 1954, but its mechanism was not identified for the 60 years since. Countless biologists and mathematics have announced hypotheses, but repeatedly failed to validate their theories.

Prof. Kim noted the fact that ‘Period 2,’ a core protein in the biological clock, dissolves in an extraordinary way. Generally, proteins dissolve incrementally faster over time. But Period 2 dissolves fast and slow, repeatedly, and thus declines in the form of steps.

As mathematician, Kim established the theory that there are two ways to form such a shape, and analyzed it through a mathematical model by using differential equation. As a result, he discovered that there are two methods in which Period 2 dissolves fast and slow, respectively, and predicted the existence of a ‘phosphorylation switch,’ which adjusts the ratio of the two methods appropriately.

If the temperatures rise above 37 degrees Celsius, the phosphorylation switch increases the portion of the method in which Period 2 dissolves slowly, and thus delays the overall speed of dissolution, and if temperatures fall below 30 degrees Celsius, the switch increases the portion of the method in which it dissolves fast to increase the speed of dissolution.

The hypothesis has been confirmed by a team led by Prof. David Bishop at Duke – National University of Singapore Medical School. The graduate school is jointly run by Duke University and the National University Singapore.

Prof. Kim said, “If we discover material that can regulate the phosphorylating switch, we will be able to prevent abnormality in biological clock that could occur due to late-hour overtime work and overseas business trips.” The study was published in the October 1 issue of ‘Molecular Cell,’ a sister journal of “Cell.”

ilju2@donga.com