Re-examining firefly bioluminescence



The highest quantum yield of firefly bioluminescence is less than half the previously accepted value of the past 50 years, suggests a report.

Bioluminescence - the ability to generate light in living organisms - as well as being intrinsically captivating, is of scientific interest because of its wide applications in the biological and environmental sciences, such as in gene-expression reporting and forensic investigation. In 1951, the highest quantum yield - the probability of photon emission per luciferin molecule - using firefly (Photinus pyralis) luciferase was first reported to be 88%. Although two years later it was said that a re-examination was needed, no further investigations were made.

Yoriko Ando and colleagues carried out a quantitative measurement of the firefly bioluminescence by using a total-photon-flux spectrometer they have developed. This spectrometer directly measures the quantitative luminescence spectra in the bioluminescence total flux, and hence can determine quantum yields. The team discovered that the highest quantum-yield value is actually only 41.0%.

The authors also reveal that the colour change in fireflies is mainly determined by the pH dependence of the green emission, again, totally opposing the widely accepted colour-change mechanism that is based on the chemical equilibrium of yellow-green and red emissions during pH change.

Author contact:
Yoriko Ando (Institute for Solid State Physics, University of Tokyo, Chiba, Japan)
Tel: +81 4 7136 3387; E-mail: yori@issp.u-tokyo.ac.jp

Imaging: Clear crystal vision



The combined power of two techniques that probe matter at the atomic scale provides information about the structure and chemical composition of a crystal at an unprecedented level of detail, say researchers.Characterizing microstructures is important in various fields of science and technology. Semiconductor devices, for example, consist of nanometre-sized components, and the performance of the devices depends on the atomic microstructure.

Koji Kimoto and co-workers combine two current microscopy methods — scanning transmission electron microscopy (STEM) and electron energy-loss spectroscopy (EELS) — having solved a number of technical problems, such as maintaining sufficient stability during measurements. This achievement allows them to continuously scan over a crystal surface, while taking spectroscopy measurements at each point. This results in two-dimensional maps of the positions of atoms of three different elements in various layers at and below the surface.

CONTACT

Koji KIMOTO (National Institute for Materials Science, Ibraki, Japan)

Tel: +81 29 860 4402; E-mail: KIMOTO.Koji@nims.go.jp