Widom, Julia R.Lee, WonbaePerdomo-Ortiz, AlejandroRappoport, DmitrijMolinski, Tadeusz F.Aspuru-Guzik, AlanMarcus, Andrew H.2015-11-242013Widom, Julia R., Wonbae Lee, Alejandro Perdomo-Ortiz, Dmitrij Rappoport, Tadeusz F. Molinski, Alán Aspuru-Guzik, and Andrew H. Marcus. 2013. Temperature-Dependent Conformations of a Membrane Supported Zinc Porphyrin Tweezer by 2D Fluorescence Spectroscopy. The Journal of Physical Chemistry A 117(29): 6171–6184.1089-5639http://nrs.harvard.edu/urn-3:HUL.InstRepos:23668110We studied the equilibrium conformations of a zinc porphyrin tweezer composed of two carboxylphenyl-functionalized zinc tetraphenyl porphyrin subunits connected by a 1,4-butyndiol spacer, which was suspended inside the amphiphilic regions of 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) liposomes. By combining phase-modulation two-dimensional fluorescence spectroscopy (2D FS) with linear absorbance and fluorimetry, we determined that the zinc porphyrin tweezer adopts a mixture of folded and extended conformations in the membrane. By fitting an exciton-coupling model to a series of data sets recorded over a range of temperatures (17–85°C) and at different laser center wavelengths, we determined that the folded form of the tweezer is stabilized by a favorable change in the entropy of the local membrane environment. Our results provide insights toward understanding the balance of thermodynamic factors that govern molecular assembly in membranes.en-USJournal Article2015-11-2410.1021/jp400394z