Probing size variations of molecular aggregates inside chlorosomes using single-object spectroscopy

Area of Science:

• Biophysics
• Photosynthesis research
• Microbiology

Background:

• Chlorosomes are highly efficient light-harvesting organelles in green bacteria.
• Bacteriochlorophyll aggregates within chlorosomes determine their optical and energy transport properties.
• The size and morphology of tubular bacteriochlorophyll aggregates are critical but challenging to measure.

Purpose of the Study:

• To theoretically investigate using single-object spectroscopy to probe size variations of bacteriochlorophyll aggregates.
• To determine if aggregate size variations within and between chlorosomes can be accessed.
• To correlate aggregate size with potential differences in growth stages or conditions.

Main Methods:

• Theoretical investigation of single-object spectroscopy techniques.
• Simulations combining single-chlorosome linear polarization-resolved spectroscopy.
• Simulations combining single-chlorosome circular dichroism spectroscopy.

Main Results:

• Demonstrated the feasibility of using combined spectroscopic methods to probe aggregate size.
• Showed that linear polarization and circular dichroism can access typical sizes of tubular aggregates.
• Indicated the potential to detect variations in aggregate size between individual chlorosomes.

Conclusions:

• Single-object spectroscopy offers a viable method for measuring bacteriochlorophyll aggregate dimensions within chlorosomes.
• This approach can reveal size heterogeneity, offering insights into chlorosome biogenesis and function.
• The findings pave the way for understanding how aggregate size impacts light-harvesting efficiency.