scholarly journals Folding Behaviour and Antibacterial Activity of Ionic Complementary Peptide EAK-16

2021 ◽  
pp. 122-130
Author(s):  
Abdul Majid ◽  
Farah Naz ◽  
Hatim Ali Jamro ◽  
Sham Lal ◽  
Inayatullah Soomro ◽  
...  
Keyword(s):  
Lipid Bilayers ◽  
Neutral Lipids ◽  
Lipid Vesicles ◽  
Aqueous Environment ◽  
Antibacterial Efficacy ◽  
Minimum Concentration ◽  
Membrane Perturbation ◽  
Structural Conformation ◽  
Membrane Interfaces ◽  
Calcein Leakage

Aim: A major challenge in the development of new antibiotics is the biocompatibility within biological environment. Ionic complementary peptide (EAK-16) from amyloid protein, have the ability to adopt secondary structure conformation at membrane interfaces. This study aimed to investigate the effect of membrane on EAK-16 peptide folding and their antibacterial applications. Methodology: We studied secondary structural conformation of EAK-16 using circular dichroism (CD) spectroscopy in an aqueous environment and at membrane bilayers interfaces. Initially, the antibacterial efficacy was investigated against both Gram-positive and Gram-negative bacteria. Membrane mimicking models were synthesised with dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylserine (DMPS) lipid vesicles using calcein leakage assay. Results: EAK-16 showed transition in secondary structural conformation. In aqueous environment, it was predominantly β-sheets and at membrane interfaces, it was mainly α-helical. EAK-16 peptide was highly active against bacteria (at minimum concentration applied) and membrane leakage was found to be > 60%. This effect was confirmed with both anionic lipids (DMPS) and neutral lipids (DMPC). The helical transition of EAK-16 could be a major factor to disrupt the membrane and bacterial death Conclusion: The secondary structural conformation and calcein leakage data suggest that EAK-16 has potential to kill bacteria by adopting helical tilted conformation and membrane perturbation via lysis. This study revealed structure-function relationship of peptide and lipid bilayers to further investigate the mode of pore formation and mode of action of EAK-16 in membrane perturbation and antibacterial efficacy.

scholarly journals Surface roughness as rupture control factor of lipid vesicles

2013 ◽  
Vol 19 (S4) ◽  
pp. 107-108 ◽  
Author(s):  
A.A. Duarte ◽  
M. Raposo
Keyword(s):  
Lipid Bilayer ◽  
Lipid Bilayers ◽  
Biological Membrane ◽  
Substrate Surface ◽  
Lipid Vesicles ◽  
Planar Lipid Bilayer ◽  
Root Mean Square Roughness ◽  
Control Factor ◽  
Formation Mechanisms ◽  
Adsorbed Amount

Liposomes or lipid vesicles are self-closed structures formed by one or several concentric lipid bilayers with an aqueous phase inside, which may incorporate almost any molecule, namely proteins, hormones, enzymes, antibiotics, anticancer agents, antifungical agents, gene transfer agents, DNA, and whole viruses. Scientific evidences prove that unprotected liposomes containing drugs are easily released from the endoplasmic reticulum of the cell. To increase the vesicles lifetime and to activate a controlled drug release with an external stimulus, the vesicles immobilization on a surface and the factors which create conditions to the liposome rupture have to be analyzed. A number of studies have identified some of the critical stages of vesicle adsorption (adhesion), fusion, deformation, rupture, and spreading of the lipid bilayer. Nevertheless, the formation mechanisms of well-controlled continuous supported bilayers or adsorption of whole liposomes are still not fully understood. As yet it was demonstrated that a controlled adsorption of vesicles containing a small fraction of charged lipids occurs without rupture and their subsequent embedding in polyelectrolyte multilayer (PEM) films, meaning vesicles may be immobilized in an intact or slightly deformed state, which can act as drug reservoirs. Moreover, depending on the nature of the physicochemical conditions of the vesicle solution and the substrate surface, a flat lipid bilayer can be formed, known as supported lipid bilayers, which can incorporate membrane proteins and keep the native dynamics of the lipid bilayer mimicking a biological membrane. In this study, a layer of 1,2-dipalmitoyl-sn-glycero-3-[phospho-rac-(1-glycerol)] (sodium salt) (DPPG) liposomes adsorbed onto PEMs cushions based on poly(ethylenimine) (PEI), poly(sodium 4-styrenesulfonate) (PSS) and poly(allylamine hydrochloride) (PAH) polyelectrolytes was analyzed by atomic force microscopy (AFM) technique in non-contact mode and quartz crystal microbalance (QCM).Sequential heterostructures of Si/PEI(PSS/PAH)4 and Si/PAH, also designated cushions, were prepared onto silicon substrates using the layer-by-layer (LbL) technique with polyelectrolyte solutions of PEI, PSS and PAH of monomeric concentrations of 0.01M. Topographic images of 1×1μm2 area of Si/PAH/DPPG (Figure 1 a), and Si/PEI(PSS/PAH)4/DPPG (Figure 1 b) LbL films were acquired by AFM. The root mean square roughness (RMS) calculated from topographies data are listed in table I. As shown, when a DPPG layer is adsorbed onto Si/PAH the RMS keeps an approximately equal value meaning that the liposome disrupted and spread onto the surface forming a planar lipid bilayer. But when a DPPG layer is adsorbed onto Si/PEI(PSS/PAH)4 the RMS value doubled, indicating that the structural integrity of the liposomes is maintained, even though there has been any deformation during adsorption. The adsorbed amount of the two PEMs and DPPG-liposomes layers was measured using a QCM and is displayed in table I. The DPPG adsorbed amount obtained on the PAH cushion was approximately equal to a planar lipid bilayer, while the adsorption onto PEI(PSS/PAH)4 was higher than the predicted for a planar lipid bilayer. This behavior suggests that the DPPG liposomes on the second PEM remained intact during adsorption. Both confirm the AFM results. Therefore we conclude that the initial roughness of the surface is a primordial factor to determine the adsorption or not of intact vesicles.The authors acknowledge the “Fundação para a Ciência e Tecnologia” (FCT-MEC) by the post-graduate scholarship SFRH/BD/62229/2009 and the “Plurianual” funding.

scholarly journals The role of surface charge in the interaction of nanoparticles with model pulmonary surfactants

Soft Matter ◽  
2018 ◽  
Vol 14 (28) ◽  
pp. 5764-5774 ◽  
Author(s):  
F. Mousseau ◽  
J.-F. Berret
Keyword(s):  
Surface Charge ◽  
Lipid Bilayers ◽  
Pulmonary Surfactant ◽  
Lipid Vesicles ◽  
Electrostatic Charge ◽  
Supported Lipid Bilayers ◽  
Pulmonary Surfactants ◽  
Inhaled Nanoparticles

Inhaled nanoparticles reaching the respiratory zone in the lungs enter first in contact with the pulmonary surfactant. It is shown here that nanoparticles and lipid vesicles formulated from different surfactant mimetics interact predominantlyviaelectrostatic charge mediated attraction and do not form supported lipid bilayers spontaneously.

scholarly journals Intracellular Lipid Droplets: From Structure to Function

2017 ◽  
Vol 10 ◽  
pp. 117863531774551 ◽  
Author(s):  
Stefano Vanni
Keyword(s):  
Lipid Droplets ◽  
Neutral Lipids ◽  
Interfacial Structure ◽  
Aqueous Environment ◽  
Sterol Esters ◽  
Computational Approaches ◽  
Main Site ◽  
Natural Surfactant ◽  
Oil Emulsions ◽  
Function Relationship

Lipid droplets (LDs) are unique intracellular organelles that are mainly constituted by neutral lipids (triglycerides, sterol esters). As such they serve as the main site of energy storage in the cell and they are akin to oil emulsions in water. To prevent the direct exposure of the hydrophobic neutral lipids to the aqueous environment of the cytosol, LDs are surrounded by a monolayer of phospholipids that thus behave as a natural surfactant. This interfacial structure is rather unique inside the cell, but a molecular understanding of how the LD structure modulates its functions is still lacking, mainly due to technical challenges in both experimental and computational approaches to investigate oil-in-water emulsions. Recently, we have investigated the structure of LDs using a combination of existing and newly developed computational approaches that are optimized to study oil-water interfaces.1 Our simulations provide a comprehensive molecular characterization of the unique surface properties of LDs, suggesting structure-function relationship in several LD-related metabolic processes.

Fusion of Lipid Vesicles with Planar Lipid Bilayers Induced by a Combination of Peptides

Langmuir ◽  
2011 ◽  
Vol 27 (20) ◽  
pp. 12515-12520 ◽  
Author(s):  
Takehiko Inaba ◽  
Yoshiro Tatsu ◽  
Kenichi Morigaki
Keyword(s):  
Lipid Bilayers ◽  
Lipid Vesicles ◽  
Planar Lipid Bilayers

scholarly journals Interaction of the cellular prion protein with raft-like lipid membranes

2007 ◽  
Vol 388 (1) ◽  
pp. 79-89 ◽  
Author(s):  
Kerstin Elfrink ◽  
Luitgard Nagel-Steger ◽  
Detlev Riesner
Keyword(s):  
Prion Protein ◽  
Lipid Bilayers ◽  
Analytical Ultracentrifugation ◽  
Chinese Hamster ◽  
Lipid Vesicles ◽  
Cellular Prion Protein ◽  
Model Membranes ◽  
Degree Of Saturation ◽  
Insertion Reaction ◽  
Chip Surface

Abstract Conversion of the cellular isoform of the prion protein (PrPC) into the disease-associated isoform (PrPSc) plays a key role in the development of prion diseases. Within its cellular pathway, PrPC undergoes several posttranslational modifications, i.e., the attachment of two N-linked glycans and a glycosyl phosphatidyl inositol (GPI) anchor, by which it is linked to the plasma membrane on the exterior cell surface. To study the interaction of PrPC with model membranes, we purified posttranslationally modified PrPC from transgenic Chinese hamster ovary (CHO) cells. The mono-, di- and oligomeric states of PrPC free in solution were analyzed by analytical ultracentrifugation. The interaction of PrPC with model membranes was studied using both lipid vesicles in solution and lipid bilayers bound to a chip surface. The equilibrium and mechanism of PrPC association with the model membranes were analyzed by surface plasmon resonance. Depending on the degree of saturation of binding sites, the concentration of PrPC released from the membrane into aqueous solution was estimated at between 10-9 and 10-7 M. This corresponds to a free energy of the insertion reaction of -48 kJ/mol. Consequences for the conversion of PrPC to PrPSc are discussed.

Cyto-insectotoxins, a novel class of cytolytic and insecticidal peptides from spider venom

2008 ◽  
Vol 411 (3) ◽  
pp. 687-696 ◽  
Author(s):  
Alexander A. Vassilevski ◽  
Sergey A. Kozlov ◽  
Olga V. Samsonova ◽  
Natalya S. Egorova ◽  
Dmitry V. Karpunin ◽  
...  
Keyword(s):  
Lipid Bilayers ◽  
Expressed Sequence Tag ◽  
Lipid Vesicles ◽  
Venom Gland ◽  
Spider Venom ◽  
Bacterial Strains ◽  
Primary Structures ◽  
Expressed Sequence ◽  
Insecticidal Peptides ◽  
Edman Sequencing

Eight linear cationic peptides with cytolytic and insecticidal activity, designated cyto-insectotoxins (CITs), were identified in Lachesana tarabaevi spider venom. The peptides showed antibiotic activity towards Gram-positive and Gram-negative bacteria at micromolar concentrations as well as toxicity to insects. The primary structures of the toxins were established by direct Edman sequencing in combination with enzymatic and chemical polypeptide degradation and MS. CITs represent a novel class of cytolytic molecules and spider venom toxins. They are the first example of molecules showing equally potent antimicrobial and insecticidal effects. Analysis of L. tarabaevi venom gland expressed sequence tag database revealed the primary structures of the protein precursors; eight peptides homologous with the purified toxins were additionally predicted. CIT precursors share a conventional prepropeptide structure with an acidic prosequence and a processing motif common to most spider toxin precursors. The most abundant peptide, CIT 1a, was chemically synthesized, and its lytic activity on different bacterial strains, human erythrocytes and lymphocytes, insect cells, planar lipid bilayers and lipid vesicles was characterized. The spider L. tarabaevi is suggested to have evolved to rely on a unique set of linear cytolytic toxins, as opposed to the more common disulfide-containing spider neurotoxins.

scholarly journals Bactericidal and membrane disruption activities of the eosinophil cationic protein are largely retained in an N-terminal fragment

2009 ◽  
Vol 421 (3) ◽  
pp. 425-434 ◽  
Author(s):  
Marc Torrent ◽  
Beatriz G. de la Torre ◽  
Victòria M. Nogués ◽  
David Andreu ◽  
Ester Boix
Keyword(s):  
Lipid Bilayers ◽  
Cell Damage ◽  
Eosinophil Cationic Protein ◽  
Lipid Vesicles ◽  
Antimicrobial Activities ◽  
Membrane Disruption ◽  
Structural Determinants ◽  
Cationic Protein ◽  
Native Proteins ◽  
Α Helix

ECP (eosinophil cationic protein) is an eosinophil secretion protein with antipathogen activities involved in the host immune defence system. The bactericidal capacity of ECP relies on its action on both the plasma membrane and the bacterial wall. In a search for the structural determinants of ECP antimicrobial activity, we have identified an N-terminal domain (residues 1–45) that retains most of ECP's membrane-destabilizing and antimicrobial activities. Two sections of this domain, ECP-(1–19) and ECP-(24–45), have also been evaluated. All three peptides bind and partially insert into lipid bilayers, inducing aggregation of lipid vesicles and leakage of their aqueous content. In such an environment, the peptides undergo conformational change, significantly increasing their α-helix content. The bactericidal activity of the three peptides against Escherichia coli and Staphylococcus aureus has been assessed at both the cytoplasmic membrane and the bacterial envelope levels. ECP-(1–45) and ECP-(24–45) partially retain the native proteins ability to bind LPS (lipopolysaccharides), and electron microscopy reveals cell damage by both peptides. Interestingly, in the E. coli cells agglutination activity of ECP is only retained by the longest segment ECP-(1–45). Comparative results suggest a task distribution, whereby residues 1–19 would contribute to membrane association and destabilization, while the 24–45 region would be essential for bactericidal action. Results also indicate that ECP cytotoxicity is not uniquely dependant on its membrane disruption capacity, and that specific interactions at the bacteria wall are also involved.

Reconstitution of the complement channel into lipid vesicles and planar bilayers starting from the fluid phase complex

1985 ◽  
Vol 5 (2) ◽  
pp. 129-136 ◽  
Author(s):  
Gianfranco Menestrina ◽  
Flavia Pasquali
Keyword(s):  
Lipid Bilayers ◽  
Membrane Attack Complex ◽  
Fluid Phase ◽  
Lipid Vesicles ◽  
Ionic Channels ◽  
Single Channels ◽  
Planar Bilayers ◽  
Low Concentrations ◽  
Host Membrane ◽  
Phase Complex

Proteolysis of the fluid phase complement complex SC5b-9 transforms it into an arnphiphilic molecule which resembles the membrane attack complex of complement and reconstitutes into lipid vesicles. Complement-containing vesicles prepared in this way can be made to fuse with planar lipid bilayers transferring their protein content to the host membrane. Massive conductance increases can thus be observed, which are due to the insertion of a large number of ionic channels into the membrane. Using low concentrations of vesicles, single channels can be studied.

scholarly journals Lysyl-Phosphatidylglycerol Attenuates Membrane Perturbation Rather than Surface Association of the Cationic Antimicrobial Peptide 6W-RP-1 in a Model Membrane System: Implications for Daptomycin Resistance

2010 ◽  
Vol 54 (10) ◽  
pp. 4476-4479 ◽  
Author(s):  
Erin Kilelee ◽  
Antje Pokorny ◽  
Michael R. Yeaman ◽  
Arnold S. Bayer
Keyword(s):  
Antimicrobial Peptide ◽  
Host Defense ◽  
Defect Formation ◽  
Lipid Vesicles ◽  
Membrane System ◽  
Cationic Antimicrobial Peptide ◽  
Membrane Perturbation ◽  
Cytoplasmic Membranes ◽  
Cationic Compounds ◽  
Membrane Defect

ABSTRACT The presence of the cationic phospholipid lysyl-phosphatidylglycerol (lysyl-PG) in staphylococcal cytoplasmic membranes has been linked to increased resistance to cationic compounds, including antibiotics such as daptomycin as well as host defense antimicrobial peptides. We investigated the effects of lysyl-PG on binding of 6W-RP-1, a synthetic antimicrobial peptide, to lipid vesicles and on peptide-induced membrane permeabilization. Unexpectedly, physiological lysyl-PG concentrations only minimally reduced membrane binding of 6W-RP-1. In contrast, 6W-RP-1-induced dye leakage was severely inhibited by lysyl-PG, suggesting that lysyl-PG primarily impacts membrane defect formation.

scholarly journals Coexistence of long and short DNA constructs within adhesion plaques

2020 ◽  
Author(s):  
Long Li ◽  
Mohammad Arif Kamal ◽  
Henning Stumpf ◽  
Franck Thibaudau ◽  
Kheya Sengupta ◽  
...  
Keyword(s):  
Lipid Bilayers ◽  
Optical Resolution ◽  
Simultaneous Action ◽  
Supported Lipid Bilayers ◽  
Physical Mechanisms ◽  
Domain Structures ◽  
Membrane Interfaces ◽  
A Cell ◽  
Physical Effects ◽  
Relative Differences

Adhesion domains forming at the membrane interfaces between two cells or a cell and the ex-tracellular matrix commonly involve multiple proteins bridges. However, the physical mechanisms governing the domain structures are not yet fully resolved. Here we present a joint experimental and theoretical study of a mimetic model-system, based on giant unilammelar vesicles interacting with supported lipid bilayers, with which the underlying physical effects can be clearly identified. In our case, adhesion is induced by simultaneous action of DNA linkers with two different lengths. We study the organization of bridges into domains as a function of relative fraction of long and short DNA constructs. Irrespective of the composition, we systematically find adhesion domains with coexisting DNA bridge types, despite their relative differences in length of 9 nm. However, at short length scales, below the optical resolution of the microscope, simulations suggest the formation of nanodomains by the minority fraction. The nano-aggregation is more significant for long bridges, which are also more stable, even though the enthalpy of membrane insertion is the same for both species.

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