Britton Chance: The Biophysicist Who Measured Fleeting Moments

Britton Chance, born on July 24, 1913, was a biochemist, biophysicist, engineer and Olympic champion whose scientific career centred on an almost impossible task: observing processes that happened too quickly, or too deep inside the body, to be seen by conventional methods.

By the first half of the twentieth century, biochemists understood that enzymes accelerated reactions inside cells. Yet many of the intermediate steps lasted only milliseconds. By the time a researcher could make a measurement, the most informative part of the reaction had already passed.

Chance approached this problem not only as a biochemist but also as an engineer.

Observing a reaction that lasts milliseconds

During the 1930s, Chance developed a miniaturized instrument for investigating rapid chemical reactions. Systems based on this approach later became widely known as stopped-flow instruments.

The principle is relatively straightforward. Two solutions are mixed at high speed and pushed into a small observation chamber. The flow is then stopped abruptly while an optical system records the changes occurring after mixing.

The chemical reaction itself is not stopped. Only the movement of the solution ends, allowing the instrument to measure light absorption repeatedly in the same reaction mixture. Changes in the signal reveal the speed of the reaction and the appearance of short-lived intermediate states.

Using his instrument, Chance obtained experimental evidence of the temporary complex formed when an enzyme binds the molecule on which it acts. Such enzyme–substrate complexes had been proposed theoretically, but their brief existence made them difficult to detect directly.

This work contributed to the development of modern enzyme kinetics, the field that examines the rates and sequences of enzyme-controlled chemical transformations. Present-day stopped-flow systems are far more sophisticated than Chance’s early apparatus, but they retain the same underlying principle.

Using light to investigate living tissue

Chance later moved from isolated enzymes to the energy metabolism of cells and tissues. He was particularly interested in mitochondria, the cellular structures that convert energy from nutrients into a form that cells can use.

Mitochondrial activity cannot be assessed simply by looking through a microscope. Molecules involved in cellular respiration, however, absorb light differently depending on their chemical state.

Chance developed spectrophotometric instruments capable of distinguishing small changes in these optical signals. Dual-wavelength spectrophotometry, for example, compared light absorption at two wavelengths and helped separate the signal of interest from interfering background changes.

These measurements allowed researchers to follow aspects of cellular respiration and oxygen use with unusually high temporal resolution.

Chance later contributed to the development of magnetic resonance spectroscopy for studying metabolism inside living organisms. Unlike a conventional anatomical image, spectroscopy can provide information about chemical compounds within tissue and the biochemical processes taking place there.

He also became one of the formative figures in biomedical optics, a field that uses light to study living tissue. Near-infrared spectroscopy became a particularly important part of this work.

Near-infrared light can penetrate a limited distance into biological tissue. Oxygenated and deoxygenated haemoglobin absorb this light differently. By analysing changes in the detected signal, researchers can indirectly estimate tissue oxygenation and aspects of blood circulation.

These principles are now used to investigate the brain, muscles and other tissues. Modern technologies rely on more precise light sources, detectors and mathematical models, so it would be inaccurate to credit Chance with inventing every current form of functional medical imaging.

His contribution was more fundamental. He helped develop the instruments and experimental logic showing that biochemical processes inside a living organism could be studied without removing or destroying the tissue.

An Olympic champion from the biochemistry laboratory

Chance’s scientific biography is unusual for another reason: he was also an accomplished competitive sailor.

At the 1952 Olympic Games in Helsinki, he served as skipper and helmsman of the American yacht Complex II. The crew competed in the 5.5 Metre class and won the gold medal after taking first place in three of the seven races.

The yacht’s name came from biochemistry. Complex II referred to an intermediate complex formed during an enzyme reaction—the kind of fleeting molecular state that Chance had spent years trying to capture with his instruments.

The connection between science and sailing in his life was more than a coincidence. Sailing requires constant attention to subtle changes in wind direction, the position of the boat and the tension of the sails. In the laboratory, Chance pursued a similar objective: he designed instruments capable of detecting small and rapid changes within complex biological systems.

Britton Chance died in 2010 at the age of 97. His legacy cannot be reduced to a single discovery. It lies in an experimental tradition that brought biology, physics and engineering together.

His career illustrates a basic principle of science: asking the right question is not always enough. Sometimes researchers must first invent the instrument that makes the answer visible.