1. ER membranes exhibit phase behavior at sites of organelle contact
Mar 16, 2020 · The membrane of the ER is thinner than the PM due to its reduced ... fluid/fluid phase separation of proteins and lipids in giant plasma membrane ...
Membrane phase behavior in cells permits transient concentration of specific proteins and lipids into dynamic nanoscopic domains. Here, we tested the existence and role of such phase behavior in endoplasmic reticulum (ER) membranes. Employing hypotonic ...
2. Intracellular Delivery by Membrane Disruption: Mechanisms, Strategies ...
As a result, the ER membrane is thinner and sparser than plasma membrane, with more unsaturated lipid tails. ... more reliable calcium readouts than commonly used ...
Intracellular delivery is a key step in biological research and has enabled decades of biomedical discoveries. It is also becoming increasingly important in industrial and medical applications ranging from biomanufacture to cell-based therapies. Here, ...
3. Free energies of membrane stalk formation from a lipidomics ... - Nature
Nov 15, 2021 · We first present a computationally efficient method for simulating thermodynamically reversible pathways of stalk formation at coarse-grained ...
Many biological membranes are asymmetric and exhibit complex lipid composition, comprising hundreds of distinct chemical species. Identifying the biological function and advantage of this complexity is a central goal of membrane biology. Here, we study how membrane complexity controls the energetics of the first steps of membrane fusions, that is, the formation of a stalk. We first present a computationally efficient method for simulating thermodynamically reversible pathways of stalk formation at coarse-grained resolution. The method reveals that the inner leaflet of a typical plasma membrane is far more fusogenic than the outer leaflet, which is likely an adaptation to evolutionary pressure. To rationalize these findings by the distinct lipid compositions, we computed ~200 free energies of stalk formation in membranes with different lipid head groups, tail lengths, tail unsaturations, and sterol content. In summary, the simulations reveal a drastic influence of the lipid composition on stalk formation and a comprehensive fusogenicity map of many biologically relevant lipid classes. Fusion of cellular membranes begins with the formation of a stalk. Here, the authors develop a computationally efficient method for coarse-grained simulations of stalk formation and apply this approach to comprehensively analyse how stalk formation is influenced by the membrane lipid composition.
4. Direct label-free imaging of nanodomains in biomimetic and ...
Feb 5, 2020 · membranes are thinner and more fluid than those of the Golgi, which are themselves thinner and more fluid than plasma membranes (PM) (Mitra, ...
The nanoscale organization of biological membranes into structurally and compositionally distinct lateral domains is believed to be central to membrane function. The nature of this organization has remained elusive due to a lack of methods to directly probe nanoscopic membrane features. We show here that cryogenic electron microscopy (cryoEM) can be used to directly image coexisting nanoscopic domains in synthetic and bio-derived membranes without extrinsic probes. Analyzing a series of single-component liposomes composed of synthetic lipids of varying lengths, we demonstrate that cryoEM can distinguish bilayer thickness differences as small as 0.5 Å, comparable to the resolution of small-angle scattering methods. Simulated images from computational models reveal that features in cryoEM images result from a complex interplay between the atomic distribution normal to the plane of the bilayer and imaging parameters. Simulations of phase separated bilayers were used to predict two sources of contrast between coexisting ordered and disordered phases within a single liposome, namely differences in membrane thickness and molecular density. We observe both sources of contrast in biomimetic membranes composed of saturated lipids, unsaturated lipids, and cholesterol. When extended to isolated mammalian plasma membranes, these methods reveal similar nanoscale lateral heterogeneities. The methods reported here for direct, probe-free imaging of nanodomains in unperturbed membranes open new avenues for investigation of nanoscopic membrane organization. SIGNIFICANCE We have used cryoEM to achieve direct, probe-free imaging of lateral domains in biomimetic lipid membranes under native conditions and to characterize differences in their structures. First, measurements of membrane thickness in laterally uniform single-component membranes show that cryoEM is capable of sub-angstrom resolution of interleaflet membrane thickness. All-atom simulations are used to predict the cryo-EM appearance of submicron domains in vesicles with coexisting liquid domains and these are quantitatively validated by direct imaging of phase separated membranes. We then extend this approach to observe nanoscopic domains in isolated cellular membranes, comprising the first direct imaging of nanodomains in biomembranes.
See AlsoWhich Of The Following Can Relatively Easily Move Laterally Within The Plasma Membrane?Which Of The Following Are Typical Components Of Biological Membranes?Which Of The Following Is Not One Of The Four Main Components Of All Plasma Membranes?When Phospholipids Are Placed In Water, They Spontaneously Form A Bilayer. Why?
5. [PDF] Biological Membrane Organization and Cellular Signaling - OSTI.gov
However, even after more than two decades since the inception of the lipid raft hypothesis, a molecular-level understanding of how lipid rafts are formed and ...
6. Membrane Curvature, Trans-Membrane Area Asymmetry ...
... typically stronger than the forces generated according to the TAA. For instance ... more easily formed on Golgi membranes than on membranes of the ER. Indeed ...
In biology, the modern scientific fashion is to mostly study proteins. Much less attention is paid to lipids. However, lipids themselves are extremely important for the formation and functioning of cellular membrane organelles. Here, the role of the geometry of the lipid bilayer in regulation of organelle shape is analyzed. It is proposed that during rapid shape transition, the number of lipid heads and their size (i.e., due to the change in lipid head charge) inside lipid leaflets modulates the geometrical properties of organelles, in particular their membrane curvature. Insertion of proteins into a lipid bilayer and the shape of protein trans-membrane domains also affect the trans-membrane asymmetry between surface areas of luminal and cytosol leaflets of the membrane. In the cases where lipid molecules with a specific shape are not predominant, the shape of lipids (cylindrical, conical, or wedge-like) is less important for the regulation of membrane curvature, due to the flexibility of their acyl chains and their high ability to diffuse.
7. Chapter 5 Flashcards by Professor Zoom | Brainscape
Saturated fatty acids tend to make the membrane less fluid ... Compared to the ER membrane, the plasma membrane contains more of which of the following (choose ...
Study Chapter 5 flashcards from Professor Zoom's class online, or in Brainscape's iPhone or Android app. ✓ Learn faster with spaced repetition.
8. Perspective: Computational modeling of accurate cellular membranes ...
Dec 10, 2018 · found that their model of leukemia plasma membranes with more than 20 lipid types simulated for 200 ns was more fluid with a KA of 0.26 N/m ...
Modeling lipid bilayers using molecular simulations has progressed from short simulations of single-component lipids to currently having the ability to model co
9. Membrane Heterogeneity Beyond the Plasma Membrane - Frontiers
Oct 2, 2020 · The ER membranes must be fluid and compliant to accommodate nascent membrane ... more disordered domains are thinner and less packed. Thus ...
The structure and organization of cellular membranes have received intense interest, particularly in investigations of the raft hypothesis. The vast majority of these investigations have focused on the plasma membrane of mammalian cells, yielding significant progress in understanding membrane heterogeneity in terms of lipid composition, molecular structure, dynamic regulation, and functional relevance. In contrast, investigations on lipid organization in other membrane systems have been comparatively scarce, despite the likely relevance of membrane domains in these contexts. In this review, we summarize recent observations on lipid organization in organellar membranes, including endoplasmic reticulum, Golgi, endo-lysosomes, lipid droplets, and secreted membranes like lung surfactant, milk fat globule membranes, and viral membranes. Across these non-plasma membrane systems, it seems that the biophysical principles underlying lipid self-organization contribute to lateral domains.
10. [PDF] Molecular Theoretical Model for Lipid Bilayers - Scholar Commons
For example, plasma membranes generally contain a greater quantity of ... notably thinner than the plasma membrane [292]. These vesicles are also highly.
11. [PDF] All-atom Modeling of Complex Cellular Membranes - NSF PAR
aeruginosa) and yeast (plasma membrane, endoplasmic reticulum, and trans-Golgi network) and more advanced ones such as plants (soybean and Arabidopsis ...
12. [PDF] Membrane curvature governs the distribution of Piezo1 in live cells
More importantly, negligible Piezo1 fluorescence was observed on membrane tethers pulled from tense blebs (Fig. 2c). Plasma membrane blebs do not contain ...
13. [PDF] a systematic study of expression and function of caenorhabditis elegans ...
The plasma membrane usually contains all of its phosphatidylserine (PS) and ... interchain van der Waals interactions, fluid lipid bilayers are thinner, more ...
14. [PDF] Lipid Membranes: From Organizational Strategies in Cells to ...
containing sphingomyelins (and which more closely mimic eukaryotic plasma membranes) have ... completely dried and then fluid containing decanoic acid vesicles ...
15. Acyl chain asymmetry and polyunsaturation of brain ... - eLife
Mar 15, 2018 · ... membranes more deformable than arachidonic acid (omega-6). These ... More generally, the flexibility of polyunsaturated phospholipids along the ...
Surrounding each living cell is a membrane that is mainly made of fat molecules called phospholipids. Similar membranes also surround many of the structures inside cells. It is important for life that these membranes are impermeable to many molecules; for example, they do not allow ions to cross them freely. The membranes also need to be flexible and allow cells to form different shapes. Flexible membranes also allow cells to move molecules around and to divide to produce new cells. Each phospholipid includes two long chains of atoms called fatty acids. There are many fatty acids but they are typically grouped into saturated and unsaturated based on their chemical structures. The omega-3 and omega-6 fats are both groups of unsaturated fatty acids that are found in brain cells. Many phospholipids in cell membranes contain one saturated and one unsaturated fatty acid but it is not clear why. By studying fat molecules in the laboratory and combining this with simulations, Manni et al. have now examined the effects of fatty acids on membranes. The investigation showed that phospholipids with both saturated and unsaturated fatty acids strike a balance between impermeable and flexible membranes. More unsaturated fatty acids make more flexible membranes but they are too permeable to be used in cells. The experiments also revealed that omega-3 unsaturated fats aid flexibility more than omega-6. This finding may help to explain why the relative amounts of omega-3 and -6 are so important in the membranes of brain cells. The connection between the fats we eat and the fatty acids in our cells is complex. Yet, findings like these serve to remind us that we need a balanced diet of different fats to keep all our cells healthy.
16. [PDF] Mechanics and Thermodynamics of Differentially Stressed Lipid ...
May 10, 2023 · ... membranes exhibit much lower lipid diffusion, and they are far more rigid than their relatively flexible fluid counterparts. Lipids with ...
17. [PDF] Plasma membranes are asymmetric in lipid unsaturation, packing and ...
May 4, 2020 · Phospholipid unsaturation is dramatically asymmetric, with the cytoplasmic leaflet being approxi- mately twofold more unsaturated than the ...
18. General discussion - RSC Publishing - The Royal Society of Chemistry
Nov 27, 2012 · ... membrane curvature of a SLB to study the ... However, one would generally expect multiple critical points in situations where three or more ...
Mr Harb opened the discussion of the paper by John Nagle: In your Introductory lecture, you showed that when the protein was inserted in the membrane, the thickness of the membrane decreased. Does this mean that the membrane became fluid and therefore the thickness decreased, or is it just a co