Energy
Transfer Observed in Live Cells Using Two-Dimensional
Electronic Spectroscopy
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Abstract
Two-dimensional
electronic spectroscopy (2DES) elucidates electronic
structure and dynamics on a femtosecond time scale and has proven
to be an incisive tool for probing congested linear spectra of biological
systems. However, samples that scatter light intensely frustrate 2DES
analysis, necessitating the use of isolated protein chromophore complexes
when studying photosynthetic energy transfer processes. We present
a method for conducting 2DES experiments that takes only seconds to
acquire thousands of 2DES spectra and permits analysis of highly scattering
samples, specifically whole cells of the purple bacterium Rhodobacter sphaeroides. These in vivo 2DES experiments
reveal similar time scales for energy transfer within the antennae
complex (light harvesting complex 2, LH2) both in the native photosynthetic
membrane environment and in isolated detergent micelles