Physical mechanisms of the interaction between lipid membranes in the aqueous environment

2015 ◽  
Vol 418 ◽  
pp. 105-125 ◽  
Author(s):  
Alexander Schlaich ◽  
Bartosz Kowalik ◽  
Matej Kanduč ◽  
Emanuel Schneck ◽  
Roland R. Netz
Keyword(s):  
Lipid Membranes ◽  
Aqueous Environment ◽  
Physical Mechanisms

scholarly journals Physical mechanisms of amyloid nucleation on fluid membranes

2020 ◽  
Vol 117 (52) ◽  
pp. 33090-33098
Author(s):  
Johannes Krausser ◽  
Tuomas P. J. Knowles ◽  
Anđela Šarić
Keyword(s):  
Lipid Membranes ◽  
Molecular Mechanisms ◽  
Amyloid Fibrils ◽  
Lipid Membrane ◽  
Coarse Grained ◽  
Coarse Grained Model ◽  
Physical Mechanisms ◽  
Fluid Membranes ◽  
Protein Membrane ◽  
Protein Rich

Biological membranes can dramatically accelerate the aggregation of normally soluble protein molecules into amyloid fibrils and alter the fibril morphologies, yet the molecular mechanisms through which this accelerated nucleation takes place are not yet understood. Here, we develop a coarse-grained model to systematically explore the effect that the structural properties of the lipid membrane and the nature of protein–membrane interactions have on the nucleation rates of amyloid fibrils. We identify two physically distinct nucleation pathways—protein-rich and lipid-rich—and quantify how the membrane fluidity and protein–membrane affinity control the relative importance of those molecular pathways. We find that the membrane’s susceptibility to reshaping and being incorporated into the fibrillar aggregates is a key determinant of its ability to promote protein aggregation. We then characterize the rates and the free-energy profile associated with this heterogeneous nucleation process, in which the surface itself participates in the aggregate structure. Finally, we compare quantitatively our data to experiments on membrane-catalyzed amyloid aggregation of α-synuclein, a protein implicated in Parkinson’s disease that predominately nucleates on membranes. More generally, our results provide a framework for understanding macromolecular aggregation on lipid membranes in a broad biological and biotechnological context.

scholarly journals Neutral lipids regulate amphipathic helix affinity for model lipid droplets

2020 ◽  
Vol 219 (4) ◽  
Author(s):  
Aymeric Chorlay ◽  
Abdou Rachid Thiam
Keyword(s):  
Neutral Lipid ◽  
Lipid Membranes ◽  
Lipid Droplets ◽  
Neutral Lipids ◽  
Aqueous Environment ◽  
Major Step ◽  
Amphipathic Helices ◽  
Binding Preference ◽  
Hydrophobic Nature ◽  
Binding Level

Cellular lipid droplets (LDs) have a neutral lipid core shielded from the aqueous environment by a phospholipid monolayer containing proteins. These proteins define the biological functions of LDs, and most of them bear amphipathic helices (AH), which can selectively target to LDs, or to LD subsets. How such binding preference happens remains poorly understood. Here, we found that artificial LDs made of different neutral lipids but presenting equal phospholipid packing densities differentially recruit AHs. Varying the phospholipid density shifts the binding levels, but the differential recruitment is unchanged. We found that the binding level of AHs is defined by their interaction preference with neutral lipids and ability to decrease surface tension. The phospholipid packing level regulates mainly the amount of neutral lipid accessible. Therefore, it is the hydrophobic nature of the phospholipid packing voids that controls the binding level of AHs. Our data bring us a major step closer to understanding the binding selectivity of AHs to lipid membranes.

scholarly journals Experimental and Computational Observations of Immunogenic Cobalt Porphyrin Lipid Bilayers: Nanodomain-Enhanced Antigen Association

Pharmaceutics ◽  
2021 ◽  
Vol 13 (1) ◽  
pp. 98
Author(s):  
Jasmin Federizon ◽  
Conrard Giresse Tetsassi Feugmo ◽  
Wei-Chiao Huang ◽  
Xuedan He ◽  
Kazutoyo Miura ◽  
...  
Keyword(s):  
Lipid Bilayers ◽  
Surface Display ◽  
Md Simulations ◽  
Nitrilotriacetic Acid ◽  
Aqueous Environment ◽  
Cobalt Porphyrin ◽  
Physical Mechanisms ◽  
Reducing Activity ◽  
The Impact ◽  
Transmission Blocking Vaccines

Cobalt porphyrin phospholipid (CoPoP) can incorporate within bilayers to enable non-covalent surface-display of antigens on liposomes by mixing with proteins bearing a polyhistidine tag (his-tag); however, the mechanisms for how this occurs are poorly understood. These were investigated using the his-tagged model antigen Pfs25, a protein antigen candidate for malaria transmission-blocking vaccines. Pfs25 was found to associate with the small molecule aquocobalamin, a form of vitamin B12 and a cobalt-containing corrin macrocycle, but without particle formation, enabling comparative assessment. Relative to CoPoP liposomes, binding and serum stability studies indicated a weaker association of Pfs25 to aquocobalamin or cobalt nitrilotriacetic acid (Co-NTA) liposomes, which have cobalt displayed in the aqueous phase on lipid headgroups. Antigen internalization by macrophages was enhanced with Pfs25 bound to CoPoP liposomes. Immunization in mice with Pfs25 bound to CoPoP liposomes elicited antibodies that recognized ookinetes and showed transmission-reducing activity. To explore the physical mechanisms involved, we employed molecular dynamics (MD) simulations of bilayers containing phospholipid, cholesterol, as well as either CoPoP or NTA-functionalized lipids. The results show that the CoPoP-containing bilayer creates nanodomains that allow access for a limited but sufficient amount of water molecules that could be replaced by his-tags due to their favorable free energy properties allowing for stabilization. The position of the metal center within the NTA liposomes was much more exposed to the aqueous environment, which could explain its limited capacity for stabilizing Pfs25. This study illustrates the impact of CoPoP-induced antigen particleization in enhancing vaccine efficacy, and provides molecular insights into the CoPoP bilayer properties that enable this.

scholarly journals Micellar Enzymology- Chemistry and Applications

2016 ◽  
Vol 10 (1) ◽  
pp. 326-334 ◽  
Author(s):  
Urvish Chhaya ◽  
Snehal Ingale
Keyword(s):  
Lipid Membranes ◽  
Reverse Micelles ◽  
Catalytic Properties ◽  
Environmental Pollutants ◽  
Aqueous Environment ◽  
Protein Chemistry ◽  
Partition Chromatography ◽  
Living Matter ◽  
Enzyme Preparations

Enzymes in aqueous environment usually deal with purified enzyme preparations isolated from living matter which does not mimic real catalytic properties in vivo. Interaction of enzymes in nature takes place with different surfaces composed from lipid membranes or they get incorporated into biomembranes. Although Water is not a dominating component in the cytoplasm but plays a structural role by participating in the formation of biocatalytic complexes like glycoproteins. Water is needed to keep biocatalyst in active confirmation and hence plays very crucial role in biocatalytic reactions, activity and stability so that it can be used for various applications. This review focuses on composition, preparation properties and parameters which influence enzymes in reverse micelles and application of micellar enzymology to study protein chemistry, shifting equilibrium of various reactions, to recover various products by partition chromatography and bioremediation of chlorophenolic environmental pollutants.

scholarly journals Insights into the Voltage Regulation Mechanism of the Pore-Forming Toxin Lysenin

Toxins ◽  
2018 ◽  
Vol 10 (8) ◽  
pp. 334
Author(s):  
Sheenah Bryant ◽  
Tyler Clark ◽  
Christopher Thomas ◽  
Kaitlyn Ware ◽  
Andrew Bogard ◽  
...  
Keyword(s):  
Lipid Membranes ◽  
Eisenia Fetida ◽  
Voltage Regulation ◽  
Aqueous Environment ◽  
Regulation Mechanism ◽  
Hydrophobic Core ◽  
Molecular Memory ◽  
Gating Mechanism ◽  
Dependent Behavior ◽  
Conducting Pathway

Lysenin, a pore forming toxin (PFT) extracted from Eisenia fetida, inserts voltage-regulated channels into artificial lipid membranes containing sphingomyelin. The voltage-induced gating leads to a strong static hysteresis in conductance, which endows lysenin with molecular memory capabilities. To explain this history-dependent behavior, we hypothesized a gating mechanism that implies the movement of a voltage domain sensor from an aqueous environment into the hydrophobic core of the membrane under the influence of an external electric field. In this work, we employed electrophysiology approaches to investigate the effects of ionic screening elicited by metal cations on the voltage-induced gating and hysteresis in conductance of lysenin channels exposed to oscillatory voltage stimuli. Our experimental data show that screening of the voltage sensor domain strongly affects the voltage regulation only during inactivation (channel closing). In contrast, channel reactivation (reopening) presents a more stable, almost invariant voltage dependency. Additionally, in the presence of anionic Adenosine 5′-triphosphate (ATP), which binds at a different site in the channel’s structure and occludes the conducting pathway, both inactivation and reactivation pathways are significantly affected. Therefore, the movement of the voltage domain sensor into a physically different environment that precludes electrostatically bound ions may be an integral part of the gating mechanism.

Interactions between biological membranes: theoretical concepts

2017 ◽  
Author(s):  
M. Kanduč ◽  
A. Schlaich ◽  
E. Schneck ◽  
R. R. Netz
Keyword(s):  
Lipid Membranes ◽  
Atomistic Simulation ◽  
Surface Interactions ◽  
Aqueous Environment ◽  
Theoretical Concepts ◽  
Simulation Techniques ◽  
Fluctuation Effects ◽  
Underlying Mechanisms ◽  
Comparable Magnitude ◽  
Interaction Free Energy

In this chapter we review the various types of generic (non-specific) forces acting between lipid membranes in an aqueous environment and discuss the underlying mechanisms, with particular focus on the competing roles of enthalpic and entropic contributions. The interaction free energy (or interaction potential) is typically the result of a subtle interplay of several, often antagonistic contributions with comparable magnitude. First, we will briefly introduce the underlying physics of various kinds of surface–surface interactions, starting with theories of van der Waals and undulation interactions, covering electrostatics, depletion, and order–parameter fluctuation effects as well. We then turn our attention to a strong and universal repulsive force at small membrane–membrane separations, namely the hydration interaction. It has been under debate and investigation for decades and is not well captured by continuum approximations, thus here we will mainly rely on atomistic simulation techniques.

scholarly journals Physical mechanisms of amyloid nucleation on fluid membranes

2019 ◽  
Author(s):  
Johannes Krausser ◽  
Tuomas P. J. Knowles ◽  
Anđela Šarić
Keyword(s):  
Lipid Membranes ◽  
Molecular Mechanisms ◽  
Amyloid Fibrils ◽  
Lipid Membrane ◽  
Coarse Grained ◽  
Coarse Grained Model ◽  
Physical Mechanisms ◽  
Membrane Affinity ◽  
Fluid Membranes ◽  
Protein Membrane

Biological membranes can dramatically accelerate the aggregation of normally soluble protein molecules into amyloid fibrils and alter the fibril morphologies, yet the molecular mechanisms through which this accelerated nucleation takes place are not yet understood. Here, we develop a coarse-grained model to systematically explore the effect that the structural properties of the lipid membrane and the nature of protein-membrane interactions have on the nucleation rates of amyloid fibrils. We identify two physically distinct nucleation pathways and quantify how the membrane fluidity and protein-membrane affinity control the relative importance of those molecular pathways. We find that the membrane’s susceptibility to reshaping and being incorporated into the fibrillar aggregates is a key determinant of its ability to promote protein aggregation. We then characterise the rates and the free energy profile associated to this heterogeneous nucleation process in which the surface itself participates in the aggregate structure. Finally, we compare quantitatively our data to experiments on membrane-catalysed amyloid aggregation of α-synuclein, a protein implicated in Parkinson’s disease that predominately nucleates on membranes. More generally, our results provide a framework for understanding macromolecular aggregation on lipid membranes in a broad biological and biotechnological context.

scholarly journals Review on optofluidic microreactors for artificial photosynthesis

2018 ◽  
Vol 9 ◽  
pp. 30-41 ◽  
Author(s):  
Xiaowen Huang ◽  
Jianchun Wang ◽  
Tenghao Li ◽  
Jianmei Wang ◽  
Min Xu ◽  
...  
Keyword(s):  
Water Splitting ◽  
Artificial Photosynthesis ◽  
Volume Ratio ◽  
Aqueous Environment ◽  
Enzymatic Reactions ◽  
Material Transport ◽  
Precise Control ◽  
Coenzyme Regeneration ◽  
Physical Mechanisms ◽  
History Of

Artificial photosynthesis (APS) mimics natural photosynthesis (NPS) to store solar energy in chemical compounds for applications such as water splitting, CO2 fixation and coenzyme regeneration. NPS is naturally an optofluidic system since the cells (typical size 10 to 100 µm) of green plants, algae, and cyanobacteria enable light capture, biochemical and enzymatic reactions and the related material transport in a microscale, aqueous environment. The long history of evolution has equipped NPS with the remarkable merits of a large surface-area-to-volume ratio, fast small molecule diffusion and precise control of mass transfer. APS is expected to share many of the same advantages of NPS and could even provide more functionality if optofluidic technology is introduced. Recently, many studies have reported on optofluidic APS systems, but there is still a lack of an in-depth review. This article will start with a brief introduction of the physical mechanisms and will then review recent progresses in water splitting, CO2 fixation and coenzyme regeneration in optofluidic APS systems, followed by discussions on pending problems for real applications.

Redox Reactions in Lipid Membranes as a Model for Primordial Energy-Conserving Systems

1997 ◽  
Vol 161 ◽  
pp. 437-442
Author(s):  
Salvatore Di Bernardo ◽  
Romana Fato ◽  
Giorgio Lenaz
Keyword(s):  
Experimental Evidence ◽  
Lipid Membranes ◽  
Energy Supply ◽  
Redox Reactions ◽  
Living Systems ◽  
Asymmetric Distribution ◽  
Conservation Of Energy ◽  
Asymmetrical Distribution ◽  
Energy Conserving ◽  
Living Organisms

AbstractOne of the peculiar aspects of living systems is the production and conservation of energy. This aspect is provided by specialized organelles, such as the mitochondria and chloroplasts, in developed living organisms. In primordial systems lacking specialized enzymatic complexes the energy supply was probably bound to the generation and maintenance of an asymmetric distribution of charged molecules in compartmentalized systems. On the basis of experimental evidence, we suggest that lipophilic quinones were involved in the generation of this asymmetrical distribution of charges through vectorial redox reactions across lipid membranes.

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