Energy Transfer Observed in Live Cells Using Two-Dimensional Electronic Spectroscopy.

Area of Science:

• Biophysics
• Spectroscopy
• Photosynthesis research

Background:

• Two-dimensional electronic spectroscopy (2DES) is crucial for studying ultrafast electronic dynamics in biological systems.
• Intense light scattering from samples like whole cells often hinders 2DES analysis.
• Previous studies typically required isolated protein chromophore complexes.

Purpose of the Study:

• To develop a rapid 2DES method for analyzing highly scattering biological samples.
• To investigate photosynthetic energy transfer in whole bacterial cells.
• To compare energy transfer dynamics in native and isolated environments.

Main Methods:

• Developed a novel 2DES experimental approach allowing rapid data acquisition (seconds).
• Applied the method to whole cells of the purple bacterium *Rhodobacter sphaeroides*.
• Analyzed *in vivo* 2DES spectra to probe energy transfer dynamics.

Main Results:

• Successfully performed 2DES on whole bacterial cells, overcoming scattering limitations.
• Acquired thousands of 2DES spectra in seconds.
• Observed comparable energy transfer timescales within the light harvesting complex 2 (LH2) in native membranes versus detergent micelles.

Conclusions:

• The new 2DES method enables *in vivo* studies of complex biological systems.
• Photosynthetic energy transfer in LH2 is robust across different environments.
• This technique opens new avenues for studying native biological processes using 2DES.