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Instruments / Technical Area	Publication Details	Published
I22-Small angle scattering & Diffraction	Viscosity-sensitive membrane dyes as tools to estimate the crystalline structure of lipid bilayers Miguel Paez-Perez , Michael R. Dent , Nicholas J. Brooks , Marina K. Kuimova Analytical Chemistry DOI: 10.1021/acs.analchem.3c01747 Diamond Proposal Number(s): [28072, 29165] Open Access Show Abstract ▼ Abstract: Lipid membranes are crucial for cellular integrity and regulation, and tight control of their structural and mechanical properties is vital to ensure that they function properly. Fluorescent probes sensitive to the membrane’s microenvironment are useful for investigating lipid membrane properties; however, there is currently a lack of quantitative correlation between the exact parameters of lipid organization and a readout from these dyes. Here, we investigate this relationship for “molecular rotors”, or microviscosity sensors, by simultaneously measuring their fluorescence lifetime to determine the membrane viscosity, while using X-ray diffraction to determine the membrane’s structural properties. Our results reveal a phase-dependent correlation between the membrane’s structural parameters and mechanical properties measured by a BODIPY-based molecular rotor, giving excellent predictive power for the structural descriptors of the lipid bilayer. We also demonstrate that differences in membrane thickness between different lipid phases are not a prerequisite for the formation of lipid microdomains and that this requirement can be disrupted by the presence of line-active molecules. Our results underpin the use of membrane-sensitive dyes as reporters of the structure of lipid membranes.	Aug 2023
I22-Small angle scattering & Diffraction	Directly imaging emergence of phase separation in peroxidized lipid membranes Miguel Paez-Perez , Aurimas Vyšniauskas , Ismael López-Duarte , Eulalie J. Lafarge , Raquel López-Ríos De Castro , Carlos M. Marques , André P. Schroder , Pierre Muller , Christian D. Lorenz , Nicholas J. Brooks , Marina K. Kuimova Communications Chemistry 6 DOI: 10.1038/s42004-022-00809-x Open Access Show Abstract ▼ Abstract: Lipid peroxidation is a process which is key in cell signaling and disease, it is exploited in cancer therapy in the form of photodynamic therapy. The appearance of hydrophilic moieties within the bilayer’s hydrocarbon core will dramatically alter the structure and mechanical behavior of membranes. Here, we combine viscosity sensitive fluorophores, advanced microscopy, and X-ray diffraction and molecular simulations to directly and quantitatively measure the bilayer’s structural and viscoelastic properties, and correlate these with atomistic molecular modelling. Our results indicate an increase in microviscosity and a decrease in the bending rigidity upon peroxidation of the membranes, contrary to the trend observed with non-oxidized lipids. Fluorescence lifetime imaging microscopy and MD simulations give evidence for the presence of membrane regions of different local order in the oxidized membranes. We hypothesize that oxidation promotes stronger lipid-lipid interactions, which lead to an increase in the lateral heterogeneity within the bilayer and the creation of lipid clusters of higher order.	Jan 2023
I22-Small angle scattering & Diffraction	Imaging non-classical mechanical responses of lipid membranes using molecular rotors Miguel Paez-Perez , Ismael López-Duarte , Aurimas Vyšniauskas , Nicholas J. Brooks , Marina K. Kuimova Chemical Science 40 DOI: 10.1039/D0SC05874B Open Access Show Abstract ▼ Abstract: Lipid packing in cellular membranes has a direct effect on membrane tension and microviscosity, and plays a central role in cellular adaptation, homeostasis and disease. According to conventional mechanical descriptions, viscosity and tension are directly interconnected, with increased tension leading to decreased membrane microviscosity. However, the intricate molecular interactions that combine to build the structure and function of a cell membrane suggest a more complex relationship between these parameters. In this work, a viscosity-sensitive fluorophore (‘molecular rotor’) is used to map changes in microviscosity in model membranes under conditions of osmotic stress. Our results suggest that the relationship between membrane tension and microviscosity is strongly influenced by the bilayer's lipid composition. In particular, we show that the effects of increasing tension are minimised for membranes that exhibit liquid disordered (Ld) – liquid ordered (Lo) phase coexistence; while, surprisingly, membranes in pure gel and Lo phases exhibit a negative compressibility behaviour, i.e. they soften upon compression.	Dec 2020
I22-Small angle scattering & Diffraction	Fatty acid membrane assembly on coacervate microdroplets as a step towards a hybrid protocell model T.-Y. Dora Tang , C. Rohaida Che Hak , Alexander J. Thompson , Marina K. Kuimova , D. S. Williams , Adam W. Perriman , Stephen Mann Nature Chemistry 6, 527533 DOI: 10.1038/nchem.1921 Show Abstract ▼ Abstract: Mechanisms of prebiotic compartmentalization are central to providing insights into how protocellular systems emerged on the early Earth. Protocell models are based predominantly on the membrane self-assembly of fatty-acid vesicles, although membrane-free scenarios that involve liquidliquid microphase separation (coacervation) have also been considered. Here we integrate these alternative models of prebiotic compartmentalization and develop a hybrid protocell model based on the spontaneous self-assembly of a continuous fatty-acid membrane at the surface of preformed coacervate microdroplets prepared from cationic peptides/polyelectrolytes and adenosine triphosphate or oligo/polyribonucleotides. We show that the coacervate-supported membrane is multilamellar, and mediates the selective uptake or exclusion of small and large molecules. The coacervate interior can be disassembled without loss of membrane integrity, and fusion and growth of the hybrid protocells can be induced under conditions of high ionic strength. Our results highlight how notions of membrane-mediated compartmentalization, chemical enrichment and internalized structuration can be integrated in protocell models via simple chemical and physical processes.	Apr 2014

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