INABA Biophoton


Research Director: Dr. Humio Inaba
(Professor, Research Institute of Electrical Communication, Tohoku University)
Research Term: 1986-1991


This project focused on the ultra-weak (《10-17 W: tens of photons per second) light that is emitted from, transmitted in, and absorbed by biological tissue and cells. These “biophotons” are quite different from known relatively intense bioluminescence emissions which are detectable by the human eye and for which specific substances are known to be responsible. The difference is in the fact that these biophotons originate completely from chemical activity within cells, and not as a response to external light, or other, stimulation.

Research Results

Single-photon counting device: A highly sensitive and reproducible biophoton emission measurement technique based primarily on single-photon counting has been developed. A second-generation version of this technique has made possible the first measurements of the quantum statistical properties of biophoton fields.

PIN/Charge Integrating Amplification (P/CIA): A PIN/Charge Integrating Amplification (P/CIA) detection technology has been developed that can be used in the detection of very weak light emission in the near-infrared region, within which certain species of oxygen emit.

Single-photon images of plant tissue: Single-photon-counting images of germinating soybeans and other plant tissues have been obtained using only the ultraweak light emitted by the specimen.

Transmission spectrophotometer: A transmission spectrophotometer based on the use of a micro-channel plate has been developed that has the highest resolution in the world for single-photon counting spectroscopy.

Fluorescence in spinach chloroplasts: Well resolved emission spectra of white light-illuminated spinach chloroplasts at room temperature show that delayed fluorescence occurs at 685 nm one second or more after excitation.

Light from sea urchin eggs: Light in the visible region was detected during the fertilization of sea urchin eggs.

Ultraweak light from mammalian nucleus: The first observation of ultraweak light emission from the mammalian nucleus was obtained.

Phase transitions in biological membranes: Studies also provided the first observations of phase transitions in biological membranes without the use of artificial chemical probes or labels.


·Various kinds of light emitting phenomena


·An image of the ultraweak photon emission penomenon accompanying soybean germination obtained for the first time by the Inaba Biophoton team. The photo shows light emission concentrated around the hypocatyl when the germ is growing and cells are actively dividing

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