Phospholipid Bilayer Membranes Research Articles

Visualization and measurement of the local absorption coefficients of single bilayer phospholipid membranes using scanning near-field optical microscopy.

Here we report the results of shear-mode thicknesses and absorption coefficient measurements made on neat membranes using scanning near-field optical microscopy (SNOM). Biomimic neat membranes composed of two different types of phoshpholipid molecules: 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and 1,2- dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) were found to exhibit different absorption coefficients under the SNOM. The localization of the lipids could be identified and correlated to the morphology of the membrane domains indicating that SNOM can be an effective and accurate approach for the label-free characterization of the structure-function relationships in cell membranes.

G-Protein-Coupled Receptor-Membrane Interactions Depend on the Receptor Activation State.

G-protein-coupled receptors (GPCRs) are the largest family of human membrane proteins and serve as primary targets of approximately one-third of currently marketed drugs. In particular, adenosine A1 receptor (A1 AR) is an important therapeutic target for treating cardiac ischemia-reperfusion injuries, neuropathic pain, and renal diseases. As a prototypical GPCR, the A1 AR is located within a phospholipid membrane bilayer and transmits cellular signals by changing between different conformational states. It is important to elucidate the lipid-protein interactions in order to understand the functional mechanism of GPCRs. Here, all-atom simulations using a robust Gaussian accelerated molecular dynamics (GaMD) method were performed on both the inactive (antagonist bound) and active (agonist and G-protein bound) A1 AR, which was embedded in a 1-palmitoyl-2-oleoyl-glycero-3-phosphocholine (POPC) lipid bilayer. In the GaMD simulations, the membrane lipids played a key role in stabilizing different conformational states of the A1 AR. Our simulations further identified important regions of the receptor that interacted distinctly with the lipids in highly correlated manner. Activation of the A1 AR led to differential dynamics in the upper and lower leaflets of the lipid bilayer. In summary, GaMD enhanced simulations have revealed strongly coupled dynamics of the GPCR and lipids that depend on the receptor activation state. © 2019 Wiley Periodicals, Inc.

Obtaining Protein Association Energy Landscape for Integral Membrane Proteins.

Integral membrane proteins are ubiquitous in biological cellular and subcellular membranes. Despite their significance to cell function, isolation of membrane proteins from their hydrophobic lipid environment and further characterization remains a challenge. To obtain insights into membrane proteins, computational approaches such as docking or self-assembly simulations have been used; however, the promise of these approaches has been limited due to the computational cost. Here we present a new approach called Protein AssociatioN Energy Landscape (PANEL) that provides an extensive and converged data set for all possible conformations of membrane protein associations using a combination of stochastic sampling and equilibration simulations. The PANEL method samples the rotational space around both interacting proteins to obtain the comprehensive interaction energy landscape. We demonstrate the versatility of the PANEL method using two distinct applications: (a) dimerization of claudin-5 tight junction proteins in phospholipid bilayer membrane and (b) dimer and trimer formation of the Outer membrane protein F (OmpF) in the lipopolysaccharide-rich bacterial outer membrane. Both applications required only a fraction of simulation cost compared to self-assembly simulations. The method is robust as it can capture changes in protein-protein conformations caused by point mutations. Moreover, the method is versatile and independent of the molecular resolution (atomistic or coarse grain) or the choice of force field employed to compute the pair-interaction energies. The PANEL method is implemented in easy-to-use scripts that are available for download for general use by the scientific community to characterize any pair of interacting integral membrane proteins.

Thermotropic Transition Behaviors of Novel Partially Fluorinated Dimyristoylphosphatidylcholines with Different Perfluoroalkyl Chain Lengths

A comparative study on the thermotropic transition of phospholipid bilayer membrane is carried out for a series of novel partially fluorinated dimyristoylphosphatidylcholines with different perfluo...

Covalent modification of phosphatidylethanolamine by 4-hydroxy-2-nonenal increases sodium permeability across phospholipid bilayer membranes

Reactive aldehydes (RAs), such as 4-hydroxy-2-nonenal (HNE) and 4-oxo-2-nonenal (ONE), produced by cells under conditions of oxidative stress, were shown to react with phosphatidylethanolamine (PE) in biological and artificial membranes. They form RA-PE adducts, which affect the function of membrane proteins by modifying various biophysical properties of the membrane. The ratio of protein to lipid in biological membranes is different, but can reach 0.25 in the membranes of oligodendrocytes. However, the impact of RA-PE adducts on permeability (P) of the neat lipid phase and molecular mechanism of their action are poorly understood. In this study, we showed that HNE increased the membrane P for ions, and in particular for sodium. This effect depended on the presence of DOPE, and was not recorded for the more toxic compound, ONE. Molecular dynamics simulations suggested that HNE-PE and ONE-PE adducts anchored different positions in the lipid bilayer, and thus changed the membrane lipid area and bilayer thickness in different ways. Sodium permeability, calculated in the presence of double HNE-PE adducts, was increased by three to four orders of magnitude when compared to PNa in adduct – free membranes. A novel mechanism by which HNE alters permeability of the lipid membrane may explain the multiple toxic or regulative effects of HNE on the function of excitable cells, such as neurons, cardiomyocytes and neurosensory cells under conditions of oxidative stress.

Voltage-Dependent Profile Structures of a Kv-Channel via Time-Resolved Neutron Interferometry

Available experimental techniques cannot determine high-resolution three-dimensional structures of membrane proteins under a transmembrane voltage. Hence, the mechanism by which voltage-gated cation channels couple conformational changes within the four voltage sensor domains, in response to either depolarizing or polarizing transmembrane voltages, to opening or closing of the pore domain's ion channel remains unresolved. Single-membrane specimens, composed of a phospholipid bilayer containing a vectorially oriented voltage-gated K+ channel protein at high in-plane density tethered to the surface of an inorganic multilayer substrate, were developed to allow the application of transmembrane voltages in an electrochemical cell. Time-resolved neutron reflectivity experiments, enhanced by interferometry enabled by the multilayer substrate, were employed to provide directly the low-resolution profile structures of the membrane containing the vectorially oriented voltage-gated K+ channel for the activated, open and deactivated, closed states of the channel under depolarizing and hyperpolarizing transmembrane voltages applied cyclically. The profile structures of these single membranes were dominated by the voltage-gated K+ channel protein because of the high in-plane density. Importantly, the use of neutrons allowed the determination of the voltage-dependent changes in both the profile structure of the membrane and the distribution of water within the profile structure. These two key experimental results were then compared to those predicted by three computational modeling approaches for the activated, open and deactivated, closed states of three different voltage-gated K+ channels in hydrated phospholipid bilayer membrane environments. Of the three modeling approaches investigated, only one state-of-the-art molecular dynamics simulation that directly predicted the response of a voltage-gated K+ channel within a phospholipid bilayer membrane to applied transmembrane voltages by utilizing very long trajectories was found to be in agreement with the two key experimental results provided by the time-resolved neutron interferometry experiments.

Membrane States of Saturated Glycerophospholipids: A Thermodynamic Study of Bilayer Phase Transitions.

Bilayer membranes formed by phospholipids vary in their membrane states by undergoing phase transitions in response to various external environmental factors. Pressure is one of these important environmental factors, but there are very few studies on the effects of pressure on phospholipid bilayer membranes. It is possible to deepen our understanding of the membrane states of phospholipid bilayer membranes by combining information regarding temperature- and/or ligand-responsivity with that regarding pressure-responsivity. In this review, we thermodynamically characterize the bilayer phase transitions of three kinds of saturated glycerophospholipids, each with a different polar head group (phosphatidyl-ethanolamine (PE), -choline (PC) or -glycerol (PG)), and explain their various membrane states depending on temperature and pressure. Both temperature- and pressure-responsivity reveal inherent features of these bilayer membranes: the metastability of the gel phase for PE bilayer membranes, the polymorphism of the gel phases for PC bilayer membranes and morphological changes in bilayer aggregates for PG bilayer membranes.

Interaction of Lorazepam with Planar Bilayer Lipid Membrane and Development of Impedimetric Sensor

Artificial planar bilayer phospholipid membrane was formed in KCl bath solutions and its electrical properties have been analyzed using electrochemical impedance spectroscopy. The stability of planar bilayer lipid membrane depends on concentration of KCl in the bath. Changes in the electrical properties of planar bilayer lipid membrane with the addition of lorazepam were also studied using electrochemical impedance spectroscopy. Lorazepam gets partitioned into bilayer lipid membrane and exhibited a fluidization effect. The ionic conductance across the bilayer lipid membrane increased with the addition of lorazepam to the bath. An impedimetric sensor was developed for quantification of lorazepam in solution.

Effect of ectoine, hydroxyectoine and β-hydroxybutyrate on the temperature and pressure stability of phospholipid bilayer membranes of different complexity.

Previous research has shown that ectoines fluidize lipid monolayers by increasing the liquid expanded region in DPPC monolayers and also decreasing the line tension responsible for the phase morphology. Here, we explored possible effects of the compatible osmolytes ectoine, hydroxyectoine and β-hydroxybutyrate on lipid bilayer membranes, including effects of temperature and pressure. The effect of the protective osmolytes on the phase transition of DPPC bilayers was investigated by fluorescence spectroscopy, differential scanning calorimetry and pressure perturbation calorimetry. A slight change of the phase behavior was observed, which resulted in a stabilization of the gel phase, which may be caused by an alteration of the hydration properties at the lipid interface and H-bond and electrostatic interactions in the headgroup region. We then explored the cosolvents' effects on giant unilamellar vesicles (GUVs) formed by lipid mixtures exhibiting phase separation into liquid-ordered (lo) and liquid-disordered (ld) domains using BODIPY-PC and the DiI18 dye as labels. The presence of both, ectoine and hydroxyectoine showed significant effects on the lateral organization increasing the fluid domains. Moreover, we observed a considerable increase in the adhesion behavior of small vesicles onto GUV surfaces. Diffusion studies by fluorescence recovery after photobleaching experiments on POPC giant vesicles quantitatively showed a hydroxyectoine-induced increase of the diffusion coefficient values, clearly demonstrating an increase in the lateral mobility of lipid within the bilayer membrane. This study provides clear evidence for the fluidizing effect of the compatible solutes on bilayer lipid membranes. A marked effect, however, was only detected if phase separated domains exist.

Towards experimental P-systems using multivesicular liposomes

P-systems are abstract computational models inspired by the phospholipid bilayer membranes generated by biological cells. Illustrated here is a mechanism by which recursive liposome structures (multivesicular liposomes) may be experimentally produced through electroformation of dipalmitoylphosphatidylcholine films for use in ‘real’ P-systems. We first present the electroformation protocol and microscopic characterisation of incident liposomes towards estimating the size of computing elements, level of internal compartment recursion, fault tolerance and stability. Following, we demonstrate multiple routes towards embedding symbols, namely modification of swelling solutions, passive diffusion, and microinjection. Finally, we discuss how computing devices based on P-systems can be produced and their current limitations.

Systemic membrane-destabilizing distress syndrome in surgery: concept, pathogenesis, diagnosis

To justify the concept of systemic membrane-destabilizing distress syndrome in surgery via analysis of phospholipid bilayer of cell membranes of various organs in urgent surgical abdominal diseases. Experimental research on dogs (n=90) included modeling of peritonitis, pancreatitis, intestinal obstruction, obstructive jaundice, and post-hemorrhagic anemia. Clinical and laboratory studies were performed in patients (n=119) with acute peritonitis, severe pancreatitis, intestinal obstruction, post-hemorrhagic anemia, acute cholecystitis, gastrointestinal bleeding, benign mechanical jaundice. Lipid profile in tissues and blood cells was determined by extraction, fractionation and densitometry. Moreover, we assessed intensity of lipid peroxidation and phospholipase activity, endogenous intoxication, functional state of organs and blood cells. It was revealed that all above-mentioned acute abdominal diseases are followed by significant changes of lipid bilayer and dysfunction of tissues in target organs, blood cells and other organs (liver, kidney, colon and small intestine, heart, lungs, spleen, brain). Changes of phospholipid bilayer are correlated with severity and course of the disease. These data were used to determine a new complex in surgery - systemic membrane-destabilizing distress syndrome. Its concept, pathogenesis, and diagnosis are presented. It was analyzed its role in development and progression of dysregulation pathology and thanatogenesis. Evidence of its importance in the pathogenesis of surgical aggression was obtained.

Systemic coagulopathic distress syndrome in surgery: concept, pathogenesis, prophylaxis

The purpose of the study is to determine the correlation of changes in the humoral and tissue components of the hemostasis system with lipid metabolism in case of various urgent surgical diseases, on the basis of which the systemic coagulopathic distress syndrome can be used as the scientific basis for the definition of a new syndrome. The work includes the results of experimental and clinical laboratory tests. Experiments on dogs: in the first group (n=18) destructive pancreatitis; in the second (n=18) - fecal peritonitis; in the third (n=15), acute obstructive intestinal obstruction; in the fourth (n=16) fecal peritonitis, in the postoperative period, Remaxol (15 ml/kg) was included in the therapy. The analysis of 55 patients with acute peritonitis, operated on for acute appendicitis, perforated gastric or duodenal ulcer, acute intestinal obstruction, acute destructive cholecystitis. In the study group (n=28), Remaxol is included in the postoperative therapy. The state of the humoral and tissue (in the experiment, the tissues of the liver, intestines, kidneys, heart, lungs, pancreas, in the clinic - tissues of the resected organs) components of the hemostasis system was evaluated, a number of lipid metabolism indicators were determined, etc. In the early periods of all investigated urgent diseases of the abdomen, pronounced changes in the system of both humoral and tissue components of the hemostasis system were revealed. The modification of the coagulation system is registered not only in the tissues of the lesion organs, but also in the target organs (system tissue hemocoagulation modifications). The research established one of the most important processes - the trigger of the hemostatic cascade reaction - is membrane-destabilizing (the source of tissue thromboplastin), which is determined by changes in the phospholipid composition of various organs tissues (involved in the pathological process or not in it). Changes in lipid metabolism are due to the activation of phospholipases and membrane lipid peroxidation in tissues. The factual material was the scientific basis for the establishment of a new syndrome. Systemic coagulopathic distress syndrome is a set of pathological processes of the body, the most important component of which is a violation of the phospholipid bilayer of blood cell membranes and organ cells due to oxidative and phospholipase induced phenomena, leading to a coagulopathic condition. It changes understanding of the prevention of thrombohemorrhagic complications, proving the effectiveness of complex therapy, including not only anticoagulants, but also drugs with membrane-stabilizing activity, in particular, Remaxol.

Study on Sucrosomial® Iron Endocytosis-Mediated Uptake and Enterocytes Release

Introduction: iron homeostasis is maintained by regulating the iron levels in plasma which is maintained by four coordinated processes: duodenal iron absorption, macrophage iron recycling, hepatic iron storage and erythropoiesis. Iron in the Fe2+ form is transported across the apical duodenal membrane by DMT1 and subsequently transferred to the blood via the iron exporter, Ferroportin the only know cell membrane iron exporter. Due to the presence of two check points at cellular levels, iron absorption and release are mainly regulated, because of this iron containing oral formulations are poorly absorbed and bioavailable. To overcome cellular barriers and increasing the bioavailability of supplemented iron forms, there is a need for new carriers that work protecting the iron as well as enhancing its intestinal absorption and release into the blood stream. Moreover thus reducing dosage and side effects. Sucrosomial® Iron (SI) represents an innovative oral iron-containing carrier in which ferric pyrophosphate is protected by a phospholipid bilayer membrane plus a sucrester matrix. To date, in vitro studies have shown that SI is mostly absorbed as vesicle-like structure, bypassing the conventional iron absorption pathway. Due to its behaviour at the gastrointestinal tract, SI is well tolerated and highly bioavailable compared to conventional iron salts. To deeply understand involvement of endocytosis in SI absorption and release, in vitro experiments using endocytosis and ferroportin inhibitors were carried outAim: to study Sucrosomial® Iron uptake and release in different in vitro systems.Materials and Methods: CACO-2 and THP1 cells were used to investigate the role of FPN in Sucorsomial Iron release from cells. For release study, CACO-2 cells were exposed for 18h to quercetin (150mmol/L) in order to downregulate FPN expression. CACO-2 quercetin pre-treated cells were co-cultured with TPH1 cells, and SI or FAC were added. However, prior to measure cell Ferritin content, the incubation medium was discarded and cells were washed to remove quercetin. Iron uptake-release analysis was performed using co-culture transwell system between CACO-2 cells and TPH1. To investigate the cellular fate of cellular iron in quercetin treated CACO-2 and TPH1 cells we measured cell ferritin content. To inhibit endocytosis absorption pathway, CACO-2, THP1 and HepG2 cells were pre-treated with PitStop2 and Dyngo 4a inhibitors and then treated with SI, or Ferrous Sulfate (FS) or ferric ammonium citrate (FAC). Cellular Ferritin content was measured.Results: in order to understand the effect of quercetin on iron storage, we used CACO2 and TPH1 cells pre-treated with quercetin and then treated with SI, FAC or nothing (control). Quercetin-SI treated CACO-2 cells showed no differences in Ferritin expression compared to control cells (3,94 ngFTL/mg proteins Vs 4,56 ngFTL/mg proteins) while in quercetin-FAC treated cells ferritin expression was decreased compare to control cells (16,3 ngFTL/mg proteins Vs 27,55 ngFTL/mg proteins). In a similar manner, quercetin-SI treated TPH1 cells didn't show increase in Ferritin expression compared to control cells (20 ngFTL/mg proteins Vs 15,15 ngFTL/mg proteins), only in quercetin-FAC treated cells we observed a Ferritin expression increase compared to control untreated cells (16 ngFTL/mg proteins Vs 24 ngFTL/mg proteins). Results from experiments using endocytosis inhibitors showed that SI absorption in CACO-2 cells is inhibited using Dyngo4a (from 4ngFTL/mg proteins to 0,36 ngFTL/ mg proteisn) while PitStop3 seems to reduce SI absorption in THP1 (from 396 ngFL/mg protein to 199,91 ngFTL/mg proteins) and HepG2 cells (from 26,86 ngFL/mg proteins to 3,93 ngFTL/mg proteins), since ferritin expression significantly decrease only in SI treated cells.Conclusions: endocytosis pathway seems to be involved in SI cellular uptake but this process is regulated in different manner probably due to different cell types. Release experiments showed that cells treated with quercetin could reduce for a negative feedback DMT1 expression as well, affecting iron uptake from cells treated with FAC but not with SI and consequently, if SI is able to bypass commonly iron uptake mechanism, FPN inhibition did not show iron release perturbation from cells treated with SI. DisclosuresBrilli:Pharmanutra s.p.a.: Consultancy. Martinelli:Janssen: Consultancy; Pfizer: Consultancy, Speakers Bureau; Celgene: Consultancy, Speakers Bureau; Roche: Consultancy; Abbvie: Consultancy; Novartis: Speakers Bureau; Amgen: Consultancy; Ariad/Incyte: Consultancy; Jazz Pharmaceuticals: Consultancy. Tarantino:Pharmanutra s.p.a.: Employment.

Safety Evaluation of Cellular-type Artificial Blood Based on Pharmacokinetic Analysis and Its Use in Medical Gas Delivery

Hemoglobin vesicles (HbVs) in which human hemoglobin is encapsulated in a phospholipid bilayer membrane (liposome) have been developed as artificial red blood cells. Although the effectiveness of HbVs, including their physicochemical characteristics and pharmacological effects, has been reported, data on the pharmacokinetic properties of HbVs are limited. Previously, we developed two kinds of radiolabeled HbV, 125I-HbV and 3H-HbV, in which the internal hemoglobin and lipid membranes were labeled with 125I and 3H, respectively. Using these isotope-labeled HbVs, we clarified the detailed pharmacokinetic properties of HbVs in healthy animals and experimental animal disease models of hemorrhagic shock, chronic cirrhosis, and hyperlipidemia. This review describes our previous results regarding the pharmacokinetic properties of HbVs, and we discuss the safety and usefulness of HbVs from the viewpoint of their pharmacokinetic characteristics. Furthermore, we have modified HbVs by employing them as a carbon monoxide (CO) carrier because the hemoglobin inside HbVs reversibly binds to CO, resulting in CO-bound HbVs (CO-HbVs). Here we report the potential of CO-HbVs for the treatment of intractable inflammatory disorders based on their therapeutic efficiency in experimental animal models.

Membrane permeabilization and perturbation induced by alkyl- biguanidium salts

ABSTRACTAlkylbiguanidium salts show membrane perturbing properties toward simple phospholipid bilayer (liposomes) and complex phospholipid membranes (bacterial membranes). Compared to metformin and phenformin, alkylbiguanidium salts induce a more significant permeabilization of the phospholipid membranes, leading to highly selective H+/OH− ion transport and subsequent depolarization of the membrane. Although alkylbiguanidium salts with shorter C6 and C8 chains are too hydrophilic to be inserted into the membrane and perturb it, those with C10, C12, C14, and C16 alkyl chains show high membrane permeabilization and depolarization activity. In addition, the C10, C12, and C14 compounds possess interesting antimicrobial activity, and, at concentrations close to their minimal inhibitory concentrations, they show low hemolytic activity and toxicity.

Light-Controlled Lipid Interaction and Membrane Organization in Photolipid Bilayer Vesicles.

Controlling lateral interactions between lipid molecules in a bilayer membrane to guide membrane organization and domain formation is a key factor for studying and emulating membrane functionality in synthetic biological systems. Here, we demonstrate an approach to reversibly control lipid organization, domain formation, and membrane stiffness of phospholipid bilayer membranes using the photoswitchable phospholipid azo-PC. azo-PC contains an azobenzene group in the sn2 acyl chain that undergoes reversible photoisomerization on illumination with UV-A and visible light. We demonstrate that the concentration of the photolipid molecules and also the assembly and disassembly of photolipids into lipid domains can be monitored by UV-vis spectroscopy because of a blue shift induced by photolipid aggregation.

Phospholipid-Dependent Mechanisms of Platelet Dysfunction in Rabbits with Hemorrhagic Shock.

The time course of phospholipid composition of platelet plasma membranes at the peak of hemorrhagic shock were studied in rabbit experiments. The results indicate the key role of impairment of the structure of platelet membrane phospholipid bilayer in the pathogenesis of shockogenic thrombocytopathy.

FT-IR spectroscopic investigation of ionizing radiation-induced damage in the small intestine of whole-body irradiated rats

Radiation-induced reactive oxygen species (ROS) initiate a myriad of oxidation reactions in the macromolecules of the biological tissues. ROS are of the primary factors responsible for induction of radiation damage in biomolecules. Polyunsaturated fatty acids (PUFAs) conforming the phospholipid membrane bilayer are highly vulnerable for the ROS attacks due to presence multiple double bonds in the PUFAs structure. The ROS-mediated oxidative degeneration of lipids is called lipid peroxidation. Freeze-dried sections from the small intestines of rats either sham, 10 cGy, 2 Gy-irradiated or rats received 10 cGy 24 h prior to a subsequent dose of 2 Gy, were examined for lipid peroxidation and protein damage using Fourier transform infrared (FT-IR) spectroscopy in spectral range 400–4000 cm−1.Our FT-IR data prove the induction of lipid peroxidation and disorder in the unsaturated lipids in the samples of all of the irradiated groups as compared with the sham-irradiated group. Lipid peroxidation was evident by the decrease in total lipid content, decrease of un-saturation level of lipids marked by the increase in the ratio saturated/unsaturated acyl chains and decrease of the integrated area under the olefinicCH absorption band. This effect was associated with significant decreases in the length of phospholipid hydrocarbon chains in all of the irradiated groups. The results also suggest a decrease in the fluidity of the cells membrane as well as possible alterations in the secondary structure of proteins. No adaptive response was seen when the 10 cGy dose preceded the 2 Gy dose. However, 10 cGy induced effects comparable to and in some cases higher than the 2 Gy dose.FT-IR spectroscopy was a powerful sensitive tool to investigate the molecular structure of lipids and proteins following x-irradiation and revealed an increase in lipid peroxidation in all irradiated groups associated with increase in the rigidity of the cell membrane and alterations in the protein secondary structure.

Applications of Magnetotactic Bacteria, Magnetosomes and Magnetosome Crystals in Biotechnology and Nanotechnology: Mini-Review.

Magnetotactic bacteria (MTB) biomineralize magnetosomes, which are defined as intracellular nanocrystals of the magnetic minerals magnetite (Fe3O4) or greigite (Fe3S4) enveloped by a phospholipid bilayer membrane. The synthesis of magnetosomes is controlled by a specific set of genes that encode proteins, some of which are exclusively found in the magnetosome membrane in the cell. Over the past several decades, interest in nanoscale technology (nanotechnology) and biotechnology has increased significantly due to the development and establishment of new commercial, medical and scientific processes and applications that utilize nanomaterials, some of which are biologically derived. One excellent example of a biological nanomaterial that is showing great promise for use in a large number of commercial and medical applications are bacterial magnetite magnetosomes. Unlike chemically-synthesized magnetite nanoparticles, magnetosome magnetite crystals are stable single-magnetic domains and are thus permanently magnetic at ambient temperature, are of high chemical purity, and display a narrow size range and consistent crystal morphology. These physical/chemical features are important in their use in biotechnological and other applications. Applications utilizing magnetite-producing MTB, magnetite magnetosomes and/or magnetosome magnetite crystals include and/or involve bioremediation, cell separation, DNA/antigen recovery or detection, drug delivery, enzyme immobilization, magnetic hyperthermia and contrast enhancement of magnetic resonance imaging. Metric analysis using Scopus and Web of Science databases from 2003 to 2018 showed that applied research involving magnetite from MTB in some form has been focused mainly in biomedical applications, particularly in magnetic hyperthermia and drug delivery.

Partitioning and Accumulation of Perfluoroalkyl Substances in Model Lipid Bilayers and Bacteria.

Perfluoroalkyl substances (PFAS) are ubiquitous and persistent environmental contaminants, yet knowledge of their biological effects and mechanisms of action is limited. The highest aqueous PFAS concentrations are found in areas where bacteria are relied upon for functions such as nutrient cycling and contaminant degradation, including fire-training areas, wastewater treatment plants, and landfill leachates. This research sought to elucidate one of the mechanisms of action of PFAS by studying their uptake by bacteria and partitioning into model phospholipid bilayer membranes. PFAS partitioned into bacteria as well as model membranes (phospholipid liposomes and bilayers). The extent of incorporation into model membranes and bacteria was positively correlated to the number of fluorinated carbons. Furthermore, incorporation was greater for perfluorinated sulfonates than for perfluorinated carboxylates. Changes in zeta potential were observed in liposomes but not bacteria, consistent with PFAS being incorporated into the phospholipid bilayer membrane. Complementary to these results, PFAS were also found to alter the gel-to-fluid phase transition temperature of phospholipid bilayers, demonstrating that PFAS affected lateral phospholipid interactions. This investigation compliments other studies showing that sulfonated PFAS and PFAS with more than seven fluorinated carbons have a higher potential to accumulate within biota than carboxylated and shorter-chain PFAS.