title: Temperature-dependent conformations of a membrane supported zinc porphyrin tweezer by 2D fluorescence spectroscopy.
abstract: We 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.
authors.affiliation: Department of Chemistry, Oregon Center for Optics, Institute of Molecular Biology, University of Oregon, Eugene, Oregon 97403, USA.
authors.forename: Julia R
authors.initials: JR
authors.lastname: Widom
authors.forename: Wonbae
authors.initials: W
authors.lastname: Lee
authors.forename: Alejandro
authors.initials: A
authors.lastname: Perdomo-Ortiz
authors.forename: Dmitrij
authors.initials: D
authors.lastname: Rappoport
authors.forename: Tadeusz F
authors.initials: TF
authors.lastname: Molinski
authors.forename: Alán
authors.initials: A
authors.lastname: Aspuru-Guzik
authors.forename: Andrew H
authors.initials: AH
authors.lastname: Marcus
mesh_terms: D019281:Dimerization; D008081:Liposomes / Q000737:chemistry*; D008665:Metalloporphyrins / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D010767:Phosphorylcholine / Q000737:chemistry; D013050:Spectrometry, Fluorescence; D013696:Temperature
chemical_list: D008081:Liposomes; D008665:Metalloporphyrins; D010767:Phosphorylcholine; C017802:zinc hematoporphyrin