LASER-INDUCED OPTOACOUSTIC SPECTROSCOPY (OAS) OF PHYTOCHROME IN-VITRO

Résumé
On étudie le phytochrome photorécepteur des plantes à l'aide d'une méthode de spectroscopie optoacoustique induite par laser. Une solution de phytochrome de (P_r) est irradiée à l'aide de pulses de 15 ns issus d'un laser à colorant accordable de 590 à 720 nm. On effectue une étude comparative à l'aide d'une solution de CuCl₂ qui présente la même absorption. Les résultats conduisent à l'interprétation de la desexcitation non radiative du système phytochromique.

Abstract
Laser-induced optoacoustic spectroscopy (OAS) has been applied to the plant photoreceptor phytochrome. A solution of purified oat phytochrome (P_r) was irradiated at room temperature with a 15 ns dye laser pulse tunable from 590 to 720 nm. The first acoustic wave was studied, which is generated by fast heat-emitting processes in less than 0.5 µs. The P_r solution emitted about 70-90 % of the heat produced by a CuCl₂ reference of the same absorbance at all wavelenghths except for 700 nm, where significantly more heat was produced by P_r. The results are interpreted in terms of a photochromic system consisting of P_r and the first intermediate in the P_r → P_fr pathway.