Spectral fine-tuning in excitonically coupled cyclic photosynthetic antennas

► Under stressed conditions the peripheral antennas called LH3 are developed. ► The absorption band of LH3 is shifted ∼50 nm to the blue as compared to regular LH2. ► In LH3 antennas the essential modification of the excitons takes place. ► Almost the entire absorption band shift in LH3 complexes has exciton origin. ► The exciton mechanism is responsible for half of the absorption band shift in LH2.