title: Communication: Coherences observed in vivo in photosynthetic bacteria using two-dimensional electronic spectroscopy.
abstract: Energy transfer through large disordered antenna networks in photosynthetic organisms can occur with a quantum efficiency of nearly 100%. This energy transfer is facilitated by the electronic structure of the photosynthetic antennae as well as interactions between electronic states and the surrounding environment. Coherences in time-domain spectroscopy provide a fine probe of how a system interacts with its surroundings. In two-dimensional electronic spectroscopy, coherences can appear on both the ground and excited state surfaces revealing detailed information regarding electronic structure, system-bath coupling, energy transfer, and energetic coupling in complex chemical systems. Numerous studies have revealed coherences in isolated photosynthetic pigment-protein complexes, but these coherences have not been observed in vivo due to the small amplitude of these signals and the intense scatter from whole cells. Here, we present data acquired using ultrafast video-acquisition gradient-assisted photon echo spectroscopy to observe quantum beating signals from coherences in vivo. Experiments were conducted on isolated light harvesting complex II (LH2) from Rhodobacter sphaeroides, whole cells of R. sphaeroides, and whole cells of R. sphaeroides grown in 30% deuterated media. A vibronic coherence was observed following laser excitation at ambient temperature between the B850 and the B850(∗) states of LH2 in each of the 3 samples with a lifetime of ∼40-60 fs.
authors.affiliation: Graduate Program in the Biophysical Sciences, Institute for Biophysical Dynamics, and The James Franck Institute, The University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: Peter D
authors.initials: PD
authors.lastname: Dahlberg
authors.affiliation: Department of Chemistry, Institute for Biophysical Dynamics, and The James Franck Institute, The University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: Graham J
authors.initials: GJ
authors.lastname: Norris
authors.affiliation: Department of Chemistry, Institute for Biophysical Dynamics, and The James Franck Institute, The University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: Cheng
authors.initials: C
authors.lastname: Wang
authors.affiliation: Department of Chemistry, Institute for Biophysical Dynamics, and The James Franck Institute, The University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: Subha
authors.initials: S
authors.lastname: Viswanathan
authors.affiliation: Department of Chemistry, Institute for Biophysical Dynamics, and The James Franck Institute, The University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: Ved P
authors.initials: VP
authors.lastname: Singh
authors.affiliation: Department of Chemistry, Institute for Biophysical Dynamics, and The James Franck Institute, The University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: Gregory S
authors.initials: GS
authors.lastname: Engel
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D017666:Deuterium Oxide; D004735:Energy Transfer / Q000502:physiology; D045342:Light-Harvesting Protein Complexes / Q000378:metabolism*; D011720:Pyrazoles; D011743:Pyrimidines; D012242:Rhodobacter sphaeroides / Q000378:metabolism*; D013057:Spectrum Analysis / Q000379:methods*; D013696:Temperature; D013997:Time Factors; D014741:Video Recording / Q000379:methods
chemical_list: C556295:4-(2-phenyl-5,7-bis(trifluoromethyl)pyrazolo(1,5-a)pyrimidin-3-yl)phenol; D001426:Bacterial Proteins; D045342:Light-Harvesting Protein Complexes; D011720:Pyrazoles; D011743:Pyrimidines; D017666:Deuterium Oxide