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Spectroscopic characterization of reaction centers of the (M)Y210W mutant of the photosynthetic bacterium Rhodobacter sphaeroides

Spectroscopic characterization of reaction centers of the (M)Y210W mutant of the photosynthetic bacterium Rhodobacter sphaeroides

Physik - Open Access LMU - Teil 01/02 vor 31 Jahren

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The tyrosine-(M)210 of the reaction center of Rhodobacter
sphaeroides 2.4.1 has been changed to a tryptophan using
site-directed mutagenesis. The reaction center of this mutant has
been characterized by low-temperature absorption and fluorescence
spectroscopy, time-resolved sub-picosecond spectroscopy, and
magnetic resonance spectroscopy. The charge separation process
showed bi-exponential kinetics at room temperature, with a main
time constant of 36 ps and an additional fast time constant of 5.1
ps. Temperature dependent fluorescence measurements predict that
the lifetime of P* becomes 4–5 times slower at cryogenic
temperatures. From EPR and absorbance-detected magnetic resonance
(ADMR, LD-ADMR) we conclude that the dimeric structure of P is not
significantly changed upon mutation. In contrast, the interaction
of the accessory bacteriochlorophyll BA with its environment
appears to be altered, possibly because of a change in its
position.