Choichi Takyu

Development of an ultra-high sensitive photon counting system and its application to biomedical measurements

Abstract The sensitivity of the photon counting method for the detection of extra-weak optical intensity was improved on the introduction of the enhanced single photoelectron counting technique incorporated with a selected photomultiplier operated under optimum conditions. With this ultra-high sensitive photon counting system it has been possible to measure the difference between the luminescence of the blood of healthy and diseased human subjects (both have extremely weak values).

Excitation of indole acetate in myeloperoxidase-H2O2 system: Possible formation of indole acetate cation radical

Abstract Myeloperoxidase-H 2 O 2 -indole acetate system at pH 7.4 emitted light in visible region. Luminescent spectrum showed a weak peak at or near 480 nm and prominent peaks at or near 550, 580, and 620 nm with deep troughs near 500 and 600 nm. In some cases, no definite peak emissions near 550 and 580 nm, but a prominent broad emission between 550 and 580 nm, is observed. Such spectral patterns in the region of 510 to 620 nm were quite similar to those report for the luminescence of photo-products formed from the indole analogs (tryptophan and indole) in 50% alcohol irradiated by U.V. (365 nm) at 77°K, assuming red shift (20–25 nm) by solvent effect. Possible formation of indole acetate cation radical (a precursor of excited indole acetate) was discussed.

Generation of electronically excited species during enzymatic oxidation of chlorpromazine and related compound

Chemiluminescence in visible region was detected, during peroxidase-catalyzed oxidation of chlorpromazine at pH7.5 (but not at pH4.25) or of propericiazine, both at pH7.5 and at pH4.25. Red colored intermediates, cation radicals, were produced and decayed in all enzymatic systems used. Chemiluminescence was also detected at pH7.5, but not at pH4.25, when synthesized cation radical of chlorpromazine in water was mixed with concentrated buffer. Protonation of alkyl nitrogen in the cation radical of chlorpromazine was highly related to the appearance of luminescence. Possible mechanisms of the generation of the excited phenothiazine analogs were discussed.

Cerenkov-type second harmonic generation from a LiNbO3 waveguide with a periodic domain grating

Abstract A Cerenkov-type second harmonic generation from a LiNbO 3 waveguide with a periodic domain grating has been studied both theoretically and experimentally. By the quasi phase-matching due to the domain grating, the output Cerenkov angle is arbitrary controlled to obtain the shallow radiated angle with good radiation profile. At the same time, the conversion efficiency increases several ten times due to the large overlapping of the fields.