Lott, Geoffrey A.Perdomo-Ortiz, AlejandroUtterback, James K.Widom, Julia R.Aspuru-Guzik, AlanMarcus, Andrew H.2012-03-182011Lott, Geoffrey A., Alejandro Perdomo-Ortiz, James K. Utterback, Julia R. Widom, Alán Aspuru-Guzik, and Andrew H. Marcus. 2011. Conformation of self-assembled porphyrin dimers in liposome vesicles by phase-modulation 2D fluorescence spectroscopy. Proceedings of the National Academy of Sciences 108(40): 16521-16526.1091-6490http://nrs.harvard.edu/urn-3:HUL.InstRepos:8404291By applying a phase-modulation fluorescence approach to 2D electronic spectroscopy, we studied the conformation-dependent exciton coupling of a porphyrin dimer embedded in a phospholipid bilayer membrane. Our measurements specify the relative angle and separation between interacting electronic transition dipole moments and thus provide a detailed characterization of dimer conformation. Phase-modulation 2D fluorescence spectroscopy (PM-2D FS) produces 2D spectra with distinct optical features, similar to those obtained using 2D photon-echo spectroscopy. Specifically, we studied magnesium meso tetraphenylporphyrin dimers, which form in the amphiphilic regions of 1,2-distearoyl-sn-glycero-3-phosphocholine liposomes. Comparison between experimental and simulated spectra show that although a wide range of dimer conformations can be inferred by either the linear absorption spectrum or the 2D spectrum alone, consideration of both types of spectra constrain the possible structures to a “T-shaped” geometry. These experiments establish the PM-2D FS method as an effective approach to elucidate chromophore dimer conformation.en-USchemical physicsbiological physicsJournal Article2012-05-0110.1073/pnas.1017308108