Temperature-Dependent Conformations of a Membrane Supported Zinc Porphyrin Tweezer by 2D Fluorescence Spectroscopy
Widom, Julia R.
Molinski, Tadeusz F.
Marcus, Andrew H.
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CitationWidom, 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.
AbstractWe 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.
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