Excitation energy transfer between monomeric bacterioclorophylls in reaction centers of P-less mutant of purple photosynthetic bacteria.

Excitation energy transfer between bacteriochlorophyll monomers in mutant bacterial reaction centers occurs within 104–98 fs, depending on temperature.

• Why it matters: Understanding these ultrafast dynamics sheds light on the physical mechanisms of photosynthetic reaction centers, which may inform the design of artificial light-harvesting systems.
• What they did: Using femtosecond differential absorption spectroscopy, the study examined the early-time excited states of B A and B B monomers in mutant RCs lacking the P dimer, analyzing spectral shifts and energy transfer rates at different wavelengths and temperatures.
• The result: The findings reveal rapid, reversible energy transfer with a ratio of forward to backward transfer rates from 2.7 to 4.4, indicating close interaction between active and inactive branches within the RC "supermolecule."