Time-Resolved Ultrafast Excitation Dynamics in the B850 Light-Harvesting Antenna from Density Functional Theory

Area of Science:

• Photosynthesis research
• Quantum biology
• Biophysics

Background:

• Antenna complexes efficiently absorb and transfer solar energy.
• Spectroscopic studies often use artificial laser excitation, differing from natural sunlight.
• Understanding excitation dynamics is key to comprehending energy transfer efficiency.

Purpose of the Study:

• To investigate the excitation dynamics of the B850 antenna ring in Rhodoblastus acidophilus.
• To compare dynamics induced by experimental laser pulses with natural processes.
• To elucidate the roles of quantum mechanical interference and nuclear motion.

Main Methods:

• Real-time density functional theory (RT-DFT) calculations.
• Simulating excitation dynamics upon short, strong laser pulse impact.
• Analyzing exciton modes and electronic density evolution.

Main Results:

• Laser pulses primarily excite the most relevant exciton modes for natural energy transfer.
• Quantum mechanical interference significantly impacts electronic distribution around 40 femtoseconds.
• Nuclear motion also influences excitation dynamics on a similar timescale.
• Excitation energy localizes on small segments of the B850 ring within 20 femtoseconds post-laser peak.

Conclusions:

• Experimental laser pulses can effectively mimic natural excitation pathways in B850 antenna complexes.
• Quantum and nuclear effects play crucial roles in ultrafast excitation dynamics.
• Energy localization dynamics are rapid and segment-specific.