scholarly journals Dendrimeric HIV-peptide delivery nanosystem affects lipid membranes structure

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Katarzyna Milowska ◽  
Aleksandra Rodacka ◽  
Sophie Melikishvili ◽  
Adam Buczkowski ◽  
Bartlomiej Pałecz ◽  
...  
Keyword(s):  
Lipid Bilayers ◽  
Lipid Membranes ◽  
Antigen Delivery ◽  
Scanning Calorimetry ◽  
Hydrophobic Domain ◽  
Langmuir Blodgett ◽  
Transmission Electron ◽  
New Information ◽  
Zwitterionic Lipids ◽  
Peptide Dendrimer

AbstractThe aim of this study was to evaluate the nature and mechanisms of interaction between HIV peptide/dendrimer complexes (dendriplex) and artificial lipid membranes, such as large unilayered vesicles (LUV) and lipid monolayers in the air–water interface. Dendriplexes were combined as one of three HIV-derived peptides (Gp160, P24 and Nef) and one of two cationic phosphorus dendrimers (CPD-G3 and CPD-G4). LUVs were formed of 1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine (DMPC) or of a mixture of DMPC and dipalmitoyl-phosphatidylglycerol (DPPG). Interactions between dendriplexes and vesicles were characterized by dynamic light scattering (DLS), fluorescence anisotropy, differential scanning calorimetry (DSC) and Langmuir–Blodgett methods. The morphology of formed systems was examined by transmission electron microscopy (TEM). The results suggest that dendriplexes interact with both hydrophobic and hydrophilic regions of lipid bilayers. The interactions between dendriplexes and negatively charged lipids (DMPC–DPPG) were stronger than those between dendriplexes and liposomes composed of zwitterionic lipids (DMPC). The former were primarily of electrostatic nature due to the positive charge of dendriplexes and the negative charge of the membrane, whereas the latter can be attributed to disturbances in the hydrophobic domain of the membrane. Obtained results provide new information about mechanisms of interaction between lipid membranes and nanocomplexes formed with HIV-derived peptides and phosphorus dendrimers. These data could be important for the choosing the appropriate antigen delivery vehicle in the new vaccines against HIV infection.

Deposition of Lipid Bilayers with Atomic Force Microscopy

2005 ◽  
Vol 11 (S03) ◽  
pp. 44-47 ◽  
Author(s):  
G. D. Tavares ◽  
M. C. de Oliveira ◽  
J. M. C. Vilela ◽  
M. S. Andrade
Keyword(s):  
Lipid Bilayers ◽  
Lipid Membranes ◽  
Force Microscopy ◽  
Langmuir Blodgett ◽  
Flat Substrate ◽  
Atomic Force ◽  
Lipid Mixtures ◽  
A Cell ◽  
Integral Proteins ◽  
Spherical Vesicles

Biological membranes are constituted of lipids organized as a two dimensional bilayer supporting peripheral and integral proteins, providing a barrier between the inside and the outside of a cell [1]. Similar membranes can be prepared from the lipid mixtures forming liposomes. The liposomes are multi or unilamellar spherical vesicles in which an aqueous volume is enclosed and can be used to encapsulate some drugs [2]. In order to better expose the details of their structure, these membranes are generally deposited on the surface of a flat substrate. These supported planar lipid membranes can also provide a model system for investigating the properties and functions of the complex cell membrane and membrane mediated processes such as recognition events and biological signal transduction. Various methods have been used to create artificial lipid membranes supported on a solid surface, being the most used the Langmuir-Blodgett monolayers formation [3], the vesicle fusion or liposome adsorption [4] and the solution spreading [5].

High-Pressure Effects on the Structure and Phase Behavior of Model Membrane Systems

1996 ◽  
Author(s):  
Roland Winter ◽  
Anne Landwehr
Keyword(s):  
High Pressure ◽  
Phase Behavior ◽  
Lipid Bilayers ◽  
Lipid Membranes ◽  
Membrane Lipids ◽  
Pressure Effects ◽  
Scanning Calorimetry ◽  
Hydrocarbon Chains ◽  
Temperature And Pressure ◽  
Lipid Conformation

Phospholipids, which provide valuable model systems for lipid membranes, display a variety of polymorphic phases, depending on their molecular structure and on environmental conditions. High hydrostatic pressure has been used as a physical parameter to study the thermodynamic properties and phase behavior of these systems. High pressure is also a characteristic feature of certain natural membrane environments. In the first part of this article, we review our recent work on the temperature- and pressure-dependent phase behavior of phospholipid systems differing in lipid conformation and headgroup structure. In the second part, we report on the determination of the (T, x, p) phase diagrams of binary phospholipid mixtures. An additional section deals with effects of incorporating ions, small amphiphilic molecules, and steroids into the bilayer on the experimental temperature- and pressure-dependent phase behavior of lipid systems. Finally, we discuss lamellar to nonlamellar thermotropic and barotropic phase transformations, which occur for a number of lipids, such as phosphatidylethanolamines, monoacylglycerides, and lipid mixtures. It has been suggested that nonlamellar lipid structures might play an important role as transient and local intermediates in a number of biochemical processes. High-pressure smallangle x-ray (SAXS) and neutron (SANS) scattering, differential scanning calorimetry (DSC), high-pressure differential thermal analysis (DTA), and p, V, T measurements have been used as experimental methods for the investigation of these systems. Lipid bilayer dispersions, in particular the phosphatidylcholines and phosphatidylethanolamines, are the workhorses for the investigation of biophysical properties of membrane lipids because they constitute the basic structural component of biological membranes. They exhibit a rich lyotropic and thermotropic phase behavior (Cevc & Marsh, 1987; Marsh, 1991; Yeagle, 1992). Most fully hydrated saturated phospholipid bilayers exhibit two principal thermotropic lamellar phase transitions, corresponding to a gel to gel (Lβ′–Pβ′) transition and a gel to liquid-crystalline (Pβ′–Lα) main transition at a temperature Tm. In the fluid-like La phase, the hydrocarbon chains of the lipid bilayers are conformationally disordered, whereas in the gel phases the hydrocarbon chains are more extended and relatively ordered.

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).

Modern TEM systems architecture

1986 ◽  
Vol 44 ◽  
pp. 602-605
Author(s):  
U. Gross ◽  
P. Hagemann
Keyword(s):  
Electron Microscope ◽  
Information Gathering ◽  
Systems Architecture ◽  
Control Functions ◽  
Transmission Electron ◽  
New Information ◽  
Comprehensive Information ◽  
Scanning Transmission ◽  
Diffraction Patterns ◽  
Analytical Equipment

By addition of analytical equipment, scanning transmission accessories and data processing equipment the basic transmission electron microscope (TEM) has evolved into a comprehensive information gathering system. This extension has led to increased complexity of the instrument as compared with the straightforward imaging microscope, since in general new information capacity has required the addition of new control hardware. The increased operational complexity is reflected in a proliferation of knobs and buttons.In the conventional electron microscope design the operating panel of the instrument has distinct control elements to alter optical conditions of the microscope column in different modes. As a consequence a multiplicity of control functions has been inevitable. Examples of this are the three pairs of focus and magnification controls needed for TEM imaging, diffraction patterns, and STEM images.

Pharmacokinetic Evaluation of 99mTc-radiolabeled Solid Lipid Nanoparticles and Chitosan Coated Solid Lipid Nanoparticles

2020 ◽  
Vol 20 (13) ◽  
pp. 1044-1052
Author(s):  
Nasrin Abbasi Gharibkandi ◽  
Sajjad Molavipordanjani ◽  
Jafar Akbari ◽  
Seyed Jalal Hosseinimehr
Keyword(s):  
Solid Lipid Nanoparticles ◽  
Lipid Nanoparticles ◽  
High Resistivity ◽  
Scanning Calorimetry ◽  
Liver Uptake ◽  
Solid Lipid ◽  
Transmission Electron ◽  
Main Portion ◽  
Pharmacokinetic Behavior

Background: Solid Lipid Nanoparticles (SLNs) possess unique in vivo features such as high resistivity, bioavailability, and habitation at the target site. Coating nanoparticles with polymers such as chitosan greatly affects their pharmacokinetic behavior, stability, tissue uptake, and controlled drug delivery. The aim of this study was to prepare and evaluate the biodistribution of 99mTc-labeled SLNs and chitosan modified SLNs in mice. Methods: 99mTc-oxine was prepared and utilized to radiolabel pre-papered SLNs or chitosan coated SLNs. After purification of radiolabeled SLNs (99mTc-SLNs) and radiolabeled chitosan-coated SLNs (99mTc-Chi-SLNs) using Amicon filter, they were injected into BALB/c mice to evaluate their biodistribution patterns. In addition, nanoparticles were characterized using Transmission Electron Microscopy (TEM), Fourier-transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), X-ray Powder Diffraction (XRD) and Dynamic Light Scattering (DLS). Results: 99mTc-oxine with high radiochemical purity (RCP~100%) and stability (RCP > 97% at 24 h) was used to provide 99mTc-SLNs and 99mTc-Chi-SLNs with high initial RCP (100%). TEM image and DLS data suggest 99mTc- SLNs susceptibility to aggregation. To that end, the main portion of 99mTc-SLNs radioactivity accumulates in the liver and intestines, while 99mTc-Chi-SLNs sequesters in the liver, intestines and kidneys. The blood radioactivity of 99mTc-Chi-SLNs was higher than that of 99mTc-SLNs by 7.5, 3.17 and 3.5 folds at 1, 4 and 8 h post-injection. 99mTc- Chi-SLNs uptake in the kidneys in comparison with 99mTc-SLNs was higher by 37.48, 5.84 and 11 folds at 1, 4 and 8h. Conclusion: The chitosan layer on the surface of 99mTc-Chi-SLNs reduces lipophilicity in comparison with 99mTc- SLNs. Therefore, 99mTc-Chi-SLNs are less susceptible to aggregation, which leads to their lower liver uptake and higher kidney uptake and blood concentration.

scholarly journals Cardiolipin-Containing Lipid Membranes Attract the Bacterial Cell Division Protein DivIVA

2021 ◽  
Vol 22 (15) ◽  
pp. 8350
Author(s):  
Naďa Labajová ◽  
Natalia Baranova ◽  
Miroslav Jurásek ◽  
Robert Vácha ◽  
Martin Loose ◽  
...  
Keyword(s):  
Cell Division ◽  
Lipid Bilayers ◽  
Bacterial Cell ◽  
Lipid Membranes ◽  
Model Organism ◽  
Active Role ◽  
Membrane Curvature ◽  
Bacterial Cell Division ◽  
Division Site ◽  
Clostridioides Difficile

DivIVA is a protein initially identified as a spatial regulator of cell division in the model organism Bacillus subtilis, but its homologues are present in many other Gram-positive bacteria, including Clostridia species. Besides its role as topological regulator of the Min system during bacterial cell division, DivIVA is involved in chromosome segregation during sporulation, genetic competence, and cell wall synthesis. DivIVA localizes to regions of high membrane curvature, such as the cell poles and cell division site, where it recruits distinct binding partners. Previously, it was suggested that negative curvature sensing is the main mechanism by which DivIVA binds to these specific regions. Here, we show that Clostridioides difficile DivIVA binds preferably to membranes containing negatively charged phospholipids, especially cardiolipin. Strikingly, we observed that upon binding, DivIVA modifies the lipid distribution and induces changes to lipid bilayers containing cardiolipin. Our observations indicate that DivIVA might play a more complex and so far unknown active role during the formation of the cell division septal membrane.

scholarly journals Study on Structure, Thermal Behavior, and Viscoelastic Properties of Nanodiamond-Reinforced Poly (vinyl alcohol) Nanocomposites

Polymers ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1426
Author(s):  
Tomáš Remiš ◽  
Petr Bělský ◽  
Tomáš Kovářík ◽  
Jaroslav Kadlec ◽  
Mina Ghafouri Azar ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Mechanical Analysis ◽  
Single Step ◽  
Poly Vinyl Alcohol ◽  
Scanning Calorimetry ◽  
X Ray Scattering ◽  
Transmission Electron ◽  
Primary Particles ◽  
Solution Casting Method ◽  
Average Size

In this work, advanced polymer nanocomposites comprising of polyvinyl alcohol (PVA) and nanodiamonds (NDs) were developed using a single-step solution-casting method. The properties of the prepared PVA/NDs nanocomposites were investigated using Raman spectroscopy, small- and wide-angle X-ray scattering (SAXS/WAXS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). It was revealed that the tensile strength improved dramatically with increasing ND content in the PVA matrix, suggesting a strong interaction between the NDs and the PVA. SEM, TEM, and SAXS showed that NDs were present in the form of agglomerates with an average size of ~60 nm with primary particles of diameter ~5 nm. These results showed that NDs could act as a good nanofiller for PVA in terms of improving its stability and mechanical properties.

scholarly journals Effect of Multiple Reflows on the Interfacial Reactions and Mechanical Properties of an Sn-0.5Cu-Al(Si) Solder and a Cu Substrate

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2367
Author(s):  
Junhyuk Son ◽  
Dong-Yurl Yu ◽  
Yun-Chan Kim ◽  
Shin-Il Kim ◽  
Min-Su Kim ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
High Heat ◽  
Interfacial Reactions ◽  
Future Application ◽  
Scanning Calorimetry ◽  
Cross Sectional ◽  
Automotive Electronic ◽  
Transmission Electron ◽  
Si Content ◽  
Lead Free Solders

In this study, the interfacial reactions and mechanical properties of solder joints after multiple reflows were observed to evaluate the applicability of the developed materials for high-temperature soldering for automotive electronic components. The microstructural changes and mechanical properties of Sn-Cu solders regarding Al(Si) addition and the number of reflows were investigated to determine their reliability under high heat and strong vibrations. Using differential scanning calorimetry, the melting points were measured to be approximately 227, 230, and 231 °C for the SC07 solder, SC-0.01Al(Si), and SC-0.03Al(Si), respectively. The cross-sectional analysis results showed that the total intermetallic compounds (IMCs) of the SC-0.03Al(Si) solder grew the least after the as-reflow, as well as after 10 reflows. Electron probe microanalysis and transmission electron microscopy revealed that the Al-Cu and Cu-Al-Sn IMCs were present inside the solders, and their amounts increased with increasing Al(Si) content. In addition, the Cu6Sn5 IMCs inside the solder became more finely distributed with increasing Al(Si) content. The Sn-0.5Cu-0.03Al(Si) solder exhibited the highest shear strength at the beginning and after 10 reflows, and ductile fracturing was observed in all three solders. This study will facilitate the future application of lead-free solders, such as an Sn-Cu-Al(Si) solder, in automotive electrical components.

scholarly journals High-Tribological-Performance Polymer Nanocomposites: An Approach Based on the Superlubricity State of the Graphene Oxide Agglomerates

Polymers ◽  
2021 ◽  
Vol 13 (14) ◽  
pp. 2237
Author(s):  
Eder H. C. Ferreira ◽  
Angela Aparecida Vieira ◽  
Lúcia Vieira ◽  
Guilhermino J. M. Fechine
Keyword(s):  
Graphene Oxide ◽  
High Viscosity ◽  
Tribological Performance ◽  
Multilayer Graphene ◽  
High Concentration ◽  
Scanning Calorimetry ◽  
Mechanical Reinforcement ◽  
Transmission Electron ◽  
Twin Screw ◽  
Mechanical Tensile

Here, nanocomposites of high-molecular-weight polyethylene (HMWPE) and HMWPE-UHMWPE (80/20 wt.%) containing a low amount of multilayer graphene oxide (mGO) (≤0.1 wt.%) were produced via twin-screw extrusion to produce materials with a higher tribological performance than UHMWPE. Due to the high viscosity of both polymers, the nanocomposites presented a significant concentration of agglomerates. However, the mechanical (tensile) and tribological (volumetric loss) performances of the nanocomposites were superior to those of UHMWPE. The morphology of the nanocomposites was investigated using differential scanning calorimetry (DSC), microtomography, and transmission electron microscopy (TEM). The explanation for these results is based on the superlubricity phenomenon of mGO agglomerates. It was also shown that the well-exfoliated mGO also contained in the nanocomposite was of fundamental importance as a mechanical reinforcement for the polymer. Even with a high concentration of agglomerates, the nanocomposites displayed tribological properties superior to UHMWPE’s (wear resistance up to 27% higher and friction coefficient up to 57% lower). Therefore, this manuscript brings a new exception to the rule, showing that agglomerates can act in a beneficial way to the mechanical properties of polymers, as long as the superlubricity phenomenon is present in the agglomerates contained in the polymer.

scholarly journals Lopinavir and Nelfinavir Induce the Accumulation of Crystalloid Lipid Inclusions within the Reservosomes of Trypanosoma cruzi and Inhibit Both Aspartyl-Type Peptidase and Cruzipain Activities Detected in These Crucial Organelles

2021 ◽  
Vol 6 (3) ◽  
pp. 120
Author(s):  
Leandro S. Sangenito ◽  
Miria G. Pereira ◽  
Thais Souto-Padron ◽  
Marta H. Branquinha ◽  
André L. S. Santos
Keyword(s):  
Trypanosoma Cruzi ◽  
Opportunistic Infections ◽  
Lipid Inclusion ◽  
Transmission Electron ◽  
New Information ◽  
Lipid Inclusions ◽  
Immunodeficiency Virus ◽  
Parasite Viability ◽  
Aspartyl Peptidases ◽  
New Evidence

Several research groups have explored the repositioning of human immunodeficiency virus aspartyl peptidase inhibitors (HIV-PIs) on opportunistic infections caused by bacteria, fungi and protozoa. In Trypanosoma cruzi, HIV-PIs have a high impact on parasite viability, and one of the main alterations promoted by this treatment is the imbalance in the parasite’s lipid metabolism. However, the reasons behind this phenomenon are unknown. In the present work, we observed by transmission electron microscopy (TEM) that the treatment of T. cruzi epimastigotes with the HIV-PIs lopinavir and nelfinavir induced a huge accumulation of crystalloid-shaped lipids within the reservosomes, most of them deforming these key organelles. As previously reported, those structures are characteristic of lipid inclusions formed mostly of cholesterol and cholesterol-esters. The fractionation of nontreated epimastigotes generated two distinct fractions enriched in reservosomes: one mostly composed of lipid inclusion-containing reservosomes (Fraction B1) and one where lipid inclusions were much less abundant (Fraction B2). Interestingly, the extract of Fraction B2 presented enzymatic activity related to aspartyl-type peptidases 3.5 times higher than that found in the extract obtained from Fraction B1. The cleavage of cathepsin D substrate by this class of peptidases was strongly impaired by pepstatin A, a prototypical aspartyl PI, and the HIV-PIs lopinavir and nelfinavir. In addition, both HIV-PIs also inhibited (to a lesser extent) the cruzipain activity present in reservosomes. Finally, our work provides new evidence concerning the presence and supposed participation of aspartyl peptidases in T. cruzi, even as it adds new information about the mechanisms behind the alterations promoted by lopinavir and nelfinavir in the protozoan.

Sign in / Sign up

Export Citation Format

Share Document