Orientation of nitro-group governs the fluorescence lifetime of nitrobenzoxadiazole (NBD)-labeled lipids in lipid bilayers

2019 ◽  
Vol 21 (4) ◽  
pp. 1682-1688 ◽  
Author(s):  
Hugo A. L. Filipe ◽  
Šárka Pokorná ◽  
Martin Hof ◽  
Mariana Amaro ◽  
Luís M. S. Loura
Keyword(s):  
Nitro Group ◽  
Lipid Bilayers ◽  
Fluorescence Lifetime ◽  
Lipid Probe

NBD fluorescence lifetime varies significantly from one lipid probe to another, despite identical fluorophore locations in the membrane. This is a consequence of differences among probes in the orientation of NBD, which determines the exposure to water of the NO2 group.

scholarly journals Understanding the photophysics and structural organization of photosynthetic proteins using model lipid membranes assembled from natural plant thylakoids

2020 ◽  
Author(s):  
Sophie A. Meredith ◽  
Takuro Yoneda ◽  
Ashley M. Hancock ◽  
Simon D. Connell ◽  
Stephen D. Evans ◽  
...  
Keyword(s):  
Lipid Bilayers ◽  
Fluorescence Lifetime ◽  
Protein Interactions ◽  
Self Assembly ◽  
High Efficiency ◽  
Complex Mixture ◽  
Direct Consequence ◽  
Model Systems ◽  
Hybrid Membranes ◽  
Model Lipid Membranes

AbstractThe light-harvesting (LH) biomembranes from photosynthetic organisms perform solar energy absorption and transfer with high efficiency. There is great interest in the nanoscale biophysics of photosynthesis, however, natural membranes are complex and highly curved so can be challenging to study. Here we present model photosynthetic “hybrid membranes” assembled from a combination of natural LH membranes and synthetic lipids deposited into a patterned polymerized lipid template on glass. This arrangement offers many advantages over previous model systems including: a sufficiently complex mixture of natural proteins to mimic the biological processes, a modular self-assembly mechanism, and a stabilizing template promoting the formation of supported lipid bilayers from complex natural membranes with high protein content (that would not otherwise form). These hybrid membranes can be used as a platform to delineate the complex relationship between LH energy pathways and membrane organization. Atomic force microscopy and fluorescence lifetime microscopy revealed that hybrid membranes have an elongated fluorescence lifetime (∼4 ns) compared to native membranes (∼0.5 ns), a direct consequence of reduced protein density and an uncoupling of protein-protein interactions. We observed the real time self-assembly and migration of LH proteins from natural membrane extracts into the hybrid membranes and monitored the photophysical state of the membranes at each stage. Finally, experiments utilizing our hybrid membranes suggest that assays currently used in the photosynthesis community to test the electron transfer activity of Photosystem II may have non-specific interactions with other proteins, implying that new methods are needed for reliable quantification of electron transfers in photosynthesis.

scholarly journals In situ, fluorescence lifetime-based measurements of cell membrane micromechanics

2019 ◽  
Author(s):  
S Son ◽  
HS Muddana ◽  
C Huang ◽  
S Zhang ◽  
PJ Butler
Keyword(s):  
Mechanical Properties ◽  
Lipid Bilayer ◽  
Lipid Bilayers ◽  
Fluorescence Lifetime ◽  
Molecular Rotor ◽  
Cell Deformability ◽  
Lifetime Distributions ◽  
Human Red Blood Cells ◽  
Area Per Lipid

ABSTRACTMicroscopic in situ measurements of the mechanical properties of lipid bilayers were derived from the mean and variance of the fluorescence lifetime distributions of 1’-dioctadecyl-3,3,3’3’-tetramethylindocarbocyanine perchlorate (DiI). In this method, DiI, incorporated into membranes, acts as a membrane-targeted molecular rotor whose fluorescence lifetime is sensitive to local lipid viscosity. A new model was developed in which changes in area per lipid were derived from the first and second moments of a stretched exponential distribution of fluorescence lifetimes of DiI, which were subsequently used to compute mean area per lipid and its variance, quantities directly related to bilayer compressibility and bending moduli. This method enabled molecular scale assays of surface micromechanics of membrane-bound entities, such as nanoliposomes and human red blood cells.STATEMENT OF SIGNIFICANCEDespite the progress in cell deformability studies, and in understanding mechanical properties of purified lipid bilayers, there has not, to date, been a method to measure the mechanics of the lipid bilayer in cells in situ. The current manuscript describes such a method. Using a fluorescent molecular rotor, DiI, embedded in the membrane, along with time resolved fluorescence, we directly measure area per lipid, and its temporal and spatial variance, properties directly related to bilayer mechanical moduli. Such a method will allow investigators to start exploring the relationship between lipid bilayer mechanics and cellular health and disease.

Observation of Concanavalin-A receptors on hydrated planar erythrocyte membrane film by in situ electron microscopy

1983 ◽  
Vol 41 ◽  
pp. 608-609
Author(s):  
Neng-Bo He ◽  
S.W. Hui
Keyword(s):  
Lipid Bilayers ◽  
Erythrocyte Membrane ◽  
Lipid Membranes ◽  
Surface Film ◽  
Biological Membranes ◽  
Electron Microscopic Observation ◽  
Electron Microscopic ◽  
Black Lipid Membranes ◽  
Fine Mesh ◽  
Planar Films

Monolayers and planar "black" lipid membranes have been widely used as models for studying the structure and properties of biological membranes. Because of the lack of a suitable method to prepare these membranes for electron microscopic observation, their ultrastructure is so far not well understood. A method of forming molecular bilayers over the holes of fine mesh grids was developed by Hui et al. to study hydrated and unsupported lipid bilayers by electron diffraction, and to image phase separated domains by diffraction contrast. We now adapted the method of Pattus et al. of spreading biological membranes vesicles on the air-water interfaces to reconstitute biological membranes into unsupported planar films for electron microscopic study. hemoglobin-free human erythrocyte membrane stroma was prepared by hemolysis. The membranes were spreaded at 20°C on balanced salt solution in a Langmuir trough until a surface pressure of 20 dyne/cm was reached. The surface film was repeatedly washed by passing to adjacent troughs over shallow partitions (fig. 1).

Effect of Integral Proteins on Frozen Membrane Fracture

1980 ◽  
Vol 38 ◽  
pp. 756-759 ◽  
Author(s):  
S. Kirchanski ◽  
D. Branton
Keyword(s):  
Lipid Bilayers ◽  
Freeze Fracture ◽  
Covalent Bond ◽  
Erythrocyte Membranes ◽  
Glycophorin A ◽  
Experimental Protocol ◽  
Transmembrane Glycoprotein ◽  
Bond Breakage ◽  
Human Erythrocyte Membranes ◽  
Integral Proteins

We have investigated the effect of integral membrane proteins upon the fracturing of frozen lipid bilayers. This investigation has been part of an effort to develop freeze fracture labeling techniques and to assess the possible breakage of covalent protein bonds during the freeze fracture process. We have developed an experimental protocol utilizing lectin affinity columns which should detect small amounts of covalent bond breakage during the fracture of liposomes containing purified (1) glycophorin (a transmembrane glycoprotein of human erythrocyte membranes). To fracture liposomes in bulk, frozen liposomes are ground repeatedly under liquid nitrogen. Failure to detect any significant covalent bond breakage (contrary to (2)) led us to question the effectiveness of our grinding procedure in fracturing and splitting lipid bilayers.

Late Stages of the “Pearling" Instability in Lipid Bilayers

1997 ◽  
Vol 7 (9) ◽  
pp. 1185-1204 ◽  
Author(s):  
J. L. Coveas ◽  
S. T. Milner ◽  
W. B. Russel
Keyword(s):  
Lipid Bilayers ◽  
Late Stages

Improved micro-impedance spectroscopy to determine cell barrier properties

2020 ◽  
Vol 4 (3) ◽  
pp. 150-155 ◽  
Author(s):  
Md. Mehadi Hasan Sohag ◽  
Olivier Nicoud ◽  
Racha Amine ◽  
Abir Khalil-Mgharbel ◽  
Jean-Pierre Alcaraz ◽  
...  
Keyword(s):  
Impedance Spectroscopy ◽  
Epithelial Cells ◽  
Lipid Bilayers ◽  
Cultured Cells ◽  
Cell Model ◽  
Measurement Techniques ◽  
Cell Monolayer ◽  
Microfluidic Channel ◽  
Small Surface ◽  
Resistance Pathway

AbstractThe goal of this study was to determine whether the Tethapod system, which was designed to determine the impedance properties of lipid bilayers, could be used for cell culture in order to utilise micro-impedance spectroscopy to examine further biological applications. To that purpose we have used normal epithelial cells from kidney (RPTEC) and a kidney cancer cell model (786-O). We demonstrate that the Tethapod system is compatible with the culture of 10,000 cells seeded to grow on a small area gold measurement electrode for several days without affecting the cell viability. Furthermore, the range of frequencies for EIS measurements were tuned to examine easily the characteristics of the cell monolayer. We demonstrate significant differences in the paracellular resistance pathway between normal and cancer kidney epithelial cells. Thus, we conclude that this device has advantages for the study of cultured cells that include (i) the configuration of measurement and reference electrodes across a microfluidic channel, and (ii) the small surface area of 6 parallel measurement electrodes (2.1 mm2) integrated in a microfluidic system. These characteristics might improve micro-impedance spectroscopy measurement techniques to provide a simple tool for further studies in the field of the patho-physiology of biological barriers.

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