By measuring how the intensity of fluorescence emitted by a fluorescent molecule changes, it is possible to infer how the molecule is moving.It is also possible to estimate the size of the molecule from the moving speed.It is a widely used measurement method in cell biology, especially because it is suitable for investigating how intracellular proteins diffuse.However, until now, there was a problem that it was not possible to measure in a very short time.Therefore, it was difficult to capture the early stages of protein formation found in brain diseases such as Alzheimer's disease.The group has developed a superconducting nanowire single photon detector (SSPD) that solves these problems and is proceeding with performance evaluation.

　And this time, we succeeded in detecting a rod-shaped molecule called QRod, which has a diameter of 7 nanometers and a length of 22 nanometers (1 nanometer is 0.000000001 meters).We were able to observe how it rotates and diffuses in the solution in a very short time.From this, it can be expected that it is possible to detect even the initial stage of proteins formed in the living body.

　This time, the result is an artificially synthesized molecule, but in the future, we plan to conduct experiments using actual proteins.If established as a measurement method, it may be an extremely effective response for diagnosing neurodegenerative diseases such as Alzheimer's disease at an extremely early stage.