X-ray 3D imaging elucidates firefly luminescence physical mechanism
The Institute of Physics NanoX team has resolved an important physical phenomenon in firefly luminescence mechanism using synchrotron x-ray phase contrast microtomography and transmission x-ray microscopy with spatial resolution <20nm.
Firefly luminescence occurs through the action of the enzyme luciferase, which combines luciferin and oxygen to make oxyluciferin in an electronically excited state and releases light as it relaxes.
While its biochemistry background was only recently established, the physical aspect remains unclear specifically where oxygen supply mechanism for light flashing is concerned.
The team resolved this problem by obtaining a detailed three-dimensional mapping of the firefly lantern – a complex microscopic structure of the tracheal system including the smallest tracheole branches (~200 nm diameter) critical for the gas exchange.
They established that the oxygen consumption corresponding to mitochondria functions exceeds the maximum rate of oxygen diffusion from the tracheal system to the photocytes and leave no room for other hypothesized control mechanisms to waste the oxygen supply.
Measurement of the energy consumption of flashing confirms that the flashing mechanism indeed uses a large portion of this maximum rate. The flashing control therefore requires the mitochondria functions, which is also require large oxygen supply, to be passivated, e.g., by nitric oxide, subsequently allowing the oxygen supply to be switched to photoluminescence.
This groundbreaking research was led by Chia-Wei Li of National Tsing Hua University and Yeu-Kuang Hwu of Academia Sinica, in collaboration with the Swiss Institution EPFL, Taiwan Endemic Species Research Institute, and Department of Entomology National Taiwan University (Phys. Rev. Lett. 2014, DOI: 10.1103/physrevlett.113.258103).