ISSN:
1573-5079
Keywords:
electron transfer
;
energy transfer
;
Photosystem One
;
picosecond absorption spectroscopy
;
primary electron acceptor A0
;
primary electron donor P700
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract It is found that the two singlet state lifetimes observed in medium sized isolated Photosystem One reaction centres belong to two distinct sets of particles. The nanosecond lifetime is due to PS1 particles in which P700 does not trap excitation energy, and the excitation energy is homogeneously distributed within the antennae of these particles. The spectral features of the picosecond component show that excitation energy in the antenna has become largely concentrated in one or more low energy (red) chlorophyll species within 3.5 ps. Antennae which have become decoupled from P700 also appear to be decoupled from these red “ancillary” chlorophylls, and this suggests that some substructure or level of organisation links them to P700. The rate of quenching of antenna singlet states appears to be independent of the redox state of P700 under the conditions used here, and oxidising P700 does not prevent excitation energy from reaching the red chlorophyll species in the antenna. We find no evidence in the data presented here of a chlorophyll molecule acting as a “metastable” primary acceptor (A0). The lower limit for the detection of such a species in these data is 20% of the optical density of the transient P700 bleach.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00048305
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