Biophysical Society Thematic Meeting| Padova 2019

Quantitative Aspects of Membrane Fusion and Fission

Poster Abstracts

17-POS Board 17 UTILIZING FRENKEL EXCITONS FOR IN SITU STUDY OF HEMI-FUSED STATE: COUNTERION DIRECTED HIERARCHICAL SELF-ASSEMBLY IN ARTIFICIAL SUPRAMOLECULAR MODEL SYSTEM Pooja V Gaikwad 1,2 ; Igor Dikiy 3 ; Anthony Cruz-Balberdy 2,4 ; Kara Ng 1,2 ; Sarah Belh 1,2 ; Nicolas Yehya 5,6 ; Nikunjkumar Visaveliya 1 ; Christopher W Leishman 1 ; Gray Huffman 1 ; Themis Lazaridis 1,2 ; Kevin Gardner 1,2,3 ; Gustavo Lopez 2,4 ; Amedee des Georges 1,2,3 ; Dorthe M Eisele 1,2 ; 1 City College of New York (CCNY) of The City University of New York (CUNY), Chemistry, New York, New York, USA 2 Graduate School and University Center of The City University of New York (CUNY), Chemistry, New York, New York, USA 3 Advanced Science Research Center (ASRC) of The City University of New York (CUNY), Chemistry, New York, New York, USA 4 Lehman College of The City University of New York (CUNY), Chemistry, New York, New York, USA 5 City College of New York (CCNY) of The City University of New York (CUNY), Physics, New York, New York, USA 6 John Hopkins University, Biophysics, Baltimore, Maryland, USA Considering its importance, it is surprising how little is known about the molecular-level mechanism of membrane fusion and its intermediate state called hemi-fusion model. In general, trapping of a hemi-fused model in time is challenging to realize without the assistance of external factors. To mitigate nature’s complexity, a common approach to investigate membrane fusion is using bottom up supramolecular model systems that are self-assembled from artificial molecules.Here we propose a highly promising artificial model system to systematically study hemi-fused intermediate: Frenkel excitonic nanotubes self-assembled from amphiphilic cyanine dye 3,30-bis(2-sulphopropyl)-5,50,6,60-tetrachloro-1,10-dioctylbenzimidacarbocyanine (abbreviated as C8S3). The system’s unique collective optical properties (Frenkel excitons) arises from the ensemble of the aggregated molecules, which are highly sensitive to the details of the molecular packing. Specifically, the dye monomers self-assemble into two distinct, well- defined morphologies; double-walled nanotubes, which self-assemble further into hemi-fused hierarchical structures, which are bundles of single-walled nanotubes. Most importantly, those two morphologies show two distinct spectroscopic signatures. This allows the use of steady-state spectroscopy as an elegant tool for in-situ investigations of the system’s structural properties during the self-assembling process. In this study, counterions with varying properties (e.g. polarizability) were employed to control the self-assembling process. We observed quantitative correlation between concentration of cation and formation of hemi-fused structure. Furthermore, for a given concentration of salt series, we found that solvated ion pairs drive the self-assembly process faster towards thermodynamic product than electrostatically bound ion pair. On the other hand, the size of the directly participating ion species (cation) had no effect on the self-assembly. Our results emphasize the high potential of the reported model system and environmental parameters for engineering a cell mimic for crucial intermediate of membrane fusion: hemi- fusion model.

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