Premium
ACOUSTIC DETECTION OF TRIPLET STATES FORMED BY RADICAL PAIR RECOMBINATION IN QUINONE‐DEPLETED PHOTOSYNTHETIC REACTION CENTERS, BY MAGNETIC FIELD MODULATION (MAGNETOPHOTOACOUSTIC EFFECT)‐A FEASIBILITY STUDY
Author(s) -
Malkin Shmuel,
Hoff Arnold J.
Publication year - 1994
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1994.tb09674.x
Subject(s) - photosynthetic reaction centre , rhodobacter sphaeroides , magnetic field , triplet state , chemistry , quinone , modulation (music) , signal (programming language) , recombination , range (aeronautics) , atomic physics , yield (engineering) , photochemistry , photoacoustic imaging in biomedicine , molecular physics , physics , photosynthesis , materials science , optics , excited state , stereochemistry , biochemistry , electron transfer , quantum mechanics , computer science , acoustics , programming language , composite material , gene , thermodynamics
An acoustic method is outlined to detect triplet states formed by radical pair recombination in photosynthetic reaction centers. It is based on magnetic field effect on the probability of triplet state formation by recombination. Using a periodically modulated magnetic field in the presence of constant exciting light, a periodic modulation of the triplet state concentration is set in the sample, which is detected through the corresponding modulated heat emission, transduced to acoustic vibration of the gas phase around the sample. This effect is similar to the photoacoustic effect, except that here the light is not modulated. The feasibility of detecting such an effect was proven experimentally, by obtaining a signal from quinone‐depleted reaction centers of Rhodobacter sphaeroides. The signal had twice the frequency of the magnetic field modulation; it was proportional to the light intensity and significantly stronger at the lower temperatures (in the investigated range 113–278 K). No signal was obtained from quinone‐containing reaction centers, which do not produce triplets. A theoretical outline of the effect and the experimental set‐up are described. The magnitude of the effect was calibrated against ordinary photoacoustic measurements, allowing numerical evaluation of certain parameters of the triplet state ( e.g. triplet energy or yield) with the aid of auxiliary information from the literature.