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News Release 09-170

Bananas Gone Bad Glow Blue in UV-Light

Holds promise for studying how organisms cleanse themselves of dying cells

Artist's illustration of how chlorophyll byproducts light up cell deconstruction in bananas.


Chlorophyll byproducts light up cell deconstruction in bananas.
Credit and Larger Version


September 9, 2009

Nicholas Turro of Columbia University, Bernhard Krautler of the University of Innsbruck, Austria and their colleagues have found that, as chlorophyll ages and begins to disintegrate in banana peels it does not change color in the spectrum of visible light we see. Instead, it glows blue when observed under ultraviolet light.

While the light show adds a level of exoticism to the fruit in our eyes, and serves to attract a host of potential consumers in the eyes of insects and other animals who can appreciate the UV, the display is equally exciting to chemists. Because the glowing molecules occur in close proximity to dying tissue, they promise to be a literal beacon for the further study of the way organisms cleanse themselves of dying cells, or programmed cell death. A well known and poorly understood condition in which programmed cell death malfunctions is cancer.

Turro and his colleagues describe how ordinary brown spots that form on bananas as they transition from ripe to rotten, each show a glowing blue halo in UV, caused by the congregation of chlorophyll breakdown byproducts. Their research appears in the Proceedings of the National Academies of Science.

Chlorophyll is the molecule that makes much of the life on earth possible. It is the integral ingredient that allows plants to take in a mixture of carbon dioxide, water and sunlight and convert it to oxygen, sugars and starches. These are the same sugars and starches we eat every time we fix a salad, and the same oxygen that we breathe.

Chlorophylls are ubiquitous on earth and their life processes are clearly visible even from outer space. As chlorophylls age and break down they can do so in spectacular displays. The most familiar of these is the red and yellow of fall foliage. However, not every chlorophyll molecule that breaks down results in red or yellow.

"This work brings to fruition some of the remarkable principles of fundamental organic photochemistry harvested from more than four decades of Professor Turro's research at Columbia" says George Kenyon, program officer in the National Science Foundation's Chemistry Division.

-NSF-

Media Contacts
Dana W. Cruikshank, NSF, (703) 292-7738, dcruiksh@nsf.gov

Program Contacts
George L. Kenyon, NSF, (703) 292-4943, gkenyon@nsf.gov

Co-Investigators
Nicholas J. Turro, Columbia University, (212) 854-2202, njt3@columbia.edu

The National Science Foundation (NSF) is an independent federal agency that supports fundamental research and education across all fields of science and engineering. In fiscal year (FY) 2017, its budget is $7.5 billion. NSF funds reach all 50 states through grants to nearly 2,000 colleges, universities and other institutions. Each year, NSF receives more than 48,000 competitive proposals for funding and makes about 12,000 new funding awards.

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Image of a ripe banana that is yellow with brown spots in visible light, but glows blue in UV.
A ripe banana is yellow with brown spots in visible light, but glows blue in UV.
Credit and Larger Version