Observing the Unobservable

In 1938, while a student at Cambridge University, Britton Chance revolutionized enzymes research. Enzymes enable the chemical reactions upon which all life depends. Scientists knew enzyme reactions were crucial but were unable to observe them because they happened too rapidly.

Tasked with observing the unobservable, Chance was inspired by the stop-motion photography experiments of 19th-century photographer Eadweard Muybridge. Muybridge used photography to capture the exact moment when a horse's hooves simultaneously leave the ground at a full gallop. Chance believed this mode of observation could be applied to observing enzyme reactions. He developed the "stopped-flow spectrophotometry" method by combining a spectrophotometer (an optical apparatus used to measure the intensity of light emitted from a particular substance) and a micro-flow apparatus (used to measure the millisecond color changes in both biological and chemical reactions). The device allowed the observation of rapid mixtures by detecting color variation. The stopped-flow method had long-ranging implications and a profound impact on scientists' abilities to understand cell metabolism and energy conversion.

Click on the images below to learn more about Chance's early work with enzymes.

1. While at Cambridge, Chance designed and built instruments to observe enzyme reactions in real time. Here are some notes outlining ideas for his stopped-flow apparatus.
2. Notes outlining ideas for Chance's stopped-flow apparatus with drawing.
3. A dual syringe system designed to mix separate enzyme solutions for the stopped-flow method.
4. The completed stopped-flow apparatus as set up in the Cambridge lab.
5. A closer look at Chance's electronics work.
6. Draft of Chance's three-part thesis which describes the process of constructing the stopped-flow apparatus.
7. After the Second World War, Chance continued his enzyme research in Stockholm with Hugo Theorell and designed a new apparatus to further elucidate the enzyme-substrate complex. Pictured here are early calculations for his dual-wavelength spectrophotometer.
8. Calculations and schematics for the dual wavelength-spectrophotometer.
9. Chance worked to develop his instrument with the American Instrument Company. This write up describes the Chance-AMINCO Dual-Wavelength/Split-Beam Recording Spectrophotometer.

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