Bacterial extracellular vesicles: towards realistic models for bacterial membranes in molecular interaction studies by surface plasmon resonance

One way to mitigate the ongoing antimicrobial resistance crisis is to discover and develop new classes of antibiotics. As all antibiotics at some point need to either cross or just interact with the bacterial membrane, there is a need for representative models of bacterial membranes and efficient methods to characterize the interactions with novel molecules -both to generate new knowledge and to screen compound libraries. Since the bacterial cell envelope is a complex assembly of lipids, lipopolysaccharides, membrane proteins and other components, constructing relevant synthetic liposome-based models of the membrane is both difficult and expensive. We here propose to let the bacteria do the hard work for us. Bacterial extracellular vesicles (bEVs) are naturally secreted by Gram-negative and Gram-positive bacteria, playing a role in communication between bacteria, as virulence factors, molecular transport or being a part of the antimicrobial resistance mechanism. bEVs consist of the bacterial outer membrane and thus inherit many components and properties of the native outer cell envelope. In this work, we have isolated and characterized bEVs from one Escherichia coli mutant and three clinical strains of the ESKAPE pathogens Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa. The bEVs were shown to be representative models for the bacterial membrane in terms of lipid composition with speciesstrain specific variations. The bEVs were further used to probe the interactions between bEV and antimicrobial peptides (AMPs) as model compounds by Surface Plasmon Resonance (SPR) and provide proof-of-principle that bEVs can be used as an easily accessible and highly realistic model for the bacterial surface in interaction studies. This further enables direct monitoring of the effect induced by antibiotics, or the response to host-pathogen interactions.

Label-free measurement of antimicrobial peptide interactions with lipid vesicles and nanodiscs using microscale thermophoresis

One strategy to combat antimicrobial resistance is the discovery of new classes of antibiotics. Most antibiotics will at some point interact with the bacterial membrane to either interfere with its integrity or to cross it. Reliable and efficient tools for determining the dissociation constant for membrane binding (KD) and the partitioning coefficient between the aqueous- and membrane phases (KP) are therefore important tools for discovering and optimizing antimicrobial hits. Here we demonstrate that microscale thermophoresis (MST) can be used for label-free measurement of KD by utilising the intrinsic fluorescence of tryptophan and thereby removing the need for chromophore labelling. As proof of principle, we have used the method to measure the binding of a set of small cyclic AMPs to large unilamellar vesicles (LUVs) and two types of lipid nanodiscs assembled by styrene maleic acid (SMA) and quaternary ammonium SMA (SMA-QA). The measured KD values correlate well with the corresponding measurements using surface plasmon resonance (SPR), also broadly reflecting the tested AMPs' minimal inhibition concentration (MIC) towards S. aureus and E. coli. We conclude that MST is a promising method for fast and cost-efficient detection of peptide-lipid interactions or mapping of sample conditions in preparation for more advanced studies that rely on expensive sample preparation, labelling and/or instrument time.

IL-17-driven induction of Paneth cell antimicrobial functions protects the host from microbiota dysbiosis and inflammation in the ileum

Interleukin (IL)-17 protects epithelial barriers by inducing the secretion of antimicrobial peptides. However, the effect of IL-17 on Paneth cells (PCs), the major producers of antimicrobial peptides in the small intestine, is unclear. Here, we show that the targeted ablation of the IL-17 receptor (IL-17R) in PCs disrupts their antimicrobial functions and decreases the frequency of ileal PCs. These changes become more pronounced after colonization with IL-17 inducing segmented filamentous bacteria. Mice with PCs that lack IL-17R show an increased inflammatory transcriptional profile in the ileum along with the severity of experimentally induced ileitis. These changes are associated with a decrease in the diversity of gut microbiota that induces a severe ileum pathology upon transfer to genetically susceptible mice, which can be prevented by the systemic administration of IL-17a/f in microbiota recipients. In an exploratory analysis of a small cohort of pediatric patients with Crohn's disease, we have found that a portion of these patients exhibits a low number of lysozyme-expressing ileal PCs and a high ileitis severity score, resembling the phenotype of mice with IL-17R-deficient PCs. Our study identifies IL-17R-dependent signaling in PCs as an important mechanism that maintains ileal homeostasis through the prevention of dysbiosis.

Goldilocks Dilemma: LPS Works Both as the Initial Target and a Barrier for the Antimicrobial Action of Cationic AMPs on E. coli

Antimicrobial peptides (AMPs) are generally membrane-active compounds that physically disrupt bacterial membranes. Despite extensive research, the precise mode of action of AMPs is still a topic of great debate. This work demonstrates that the initial interaction between the Gram-negative E. coli and AMPs is driven by lipopolysaccharides (LPS) that act as kinetic barriers for the binding of AMPs to the bacterial membrane. A combination of SPR and NMR experiments provide evidence suggesting that cationic AMPs first bind to the negatively charged LPS before reaching a binding place in the lipid bilayer. In the event that the initial LPS-binding is too strong (corresponding to a low dissociation rate), the cationic AMPs cannot effectively get from the LPS to the membrane, and their antimicrobial potency will thus be diminished. On the other hand, the AMPs must also be able to effectively interact with the membrane to exert its activity. The ability of the studied cyclic hexapeptides to bind LPS and to translocate into a lipid membrane is related to the nature of the cationic charge (arginine vs. lysine) and to the distribution of hydrophobicity along the molecule (alternating vs. clumped tryptophan).

Contrasting the phospholipid profiles of two neoplastic cell lines reveal a high PC:PE ratio for SH-SY5Y cells relative to A431 cells

Lipids have been implicated in Parkinson's Disease (PD). We therefore studied the lipid profile of the neuroblastoma SH-SY5Y cell line, which is used extensively in PD research and compared it to that of the A431 epithelial cancer cell line. We have isolated whole cell extracts (WC) and plasma membrane (PM) fractions of both cell lines. The isolates were analyzed with ³¹P NMR. We observed a significant higher abundance of phosphatidylcholine (PC) for SH-SY5Y cells for both WC (55 ± 4.1%) and PM (63.3 ± 3.1%) compared to WC (40.5 ± 2.2%) and PM (43.4 ± 1.3%) of A431. Moreover, a higher abundance of phosphatidylethanolamine was detected for the WC of A431 compared to the SH-SY5Y. Using LC-MS/MS, we also determined the relative abundance of fatty acid (FA) moieties for each phospholipid class, finding that SH-SY5Y had high polyunsaturated FA levels, including arachidonic acid compared to A431 cells. When comparing our results to reported compositions of brain and neural tissues, we note the much higher PC levels, as well as very low levels of docosahexaenoic acid. However, relative levels of arachidonic acid and other polyunsaturated fatty acids were elevated, in line with what is desirable for a neural model system.

Long-read single-molecule RNA structure sequencing using nanopore

RNA molecules can form secondary and tertiary structures that can regulate their localization and function. Using enzymatic or chemical probing together with high-throughput sequencing, secondary structure can be mapped across the entire transcriptome. However, a limiting factor is that only population averages can be obtained since each read is an independent measurement. Although long-read sequencing has recently been used to determine RNA structure, these methods still used aggregate signals across the strands to detect structure. Averaging across the population also means that only limited information about structural heterogeneity across molecules or dependencies within each molecule can be obtained. Here, we present Single-Molecule Structure sequencing (SMS-seq) that combines structural probing with native RNA sequencing to provide non-amplified, structural profiles of individual molecules with novel analysis methods. Our new approach using mutual information enabled single molecule structural interrogation. Each RNA is probed at numerous bases enabling the discovery of dependencies and heterogeneity of structural features. We also show that SMS-seq can capture tertiary interactions, dynamics of riboswitch ligand binding, and mRNA structural features.

Synthesis of 2-Phospha[7]helicene, a Helicene with a Terminal Phosphinine Ring

A synthetic strategy toward phosphahelicenes containing a terminal phosphinine ring has been explored. The 4-phenyl-6-methyl-2-phospha[7]helicene was prepared from starting 2-bromobenzo[c]phenanthrene in 12% overall yield in 12 steps. The synthetic approach involves introduction of the phosphorus function prior to photocyclization forming the final helicene skeleton, followed by the formation of a phosphorus hexacycle. The structure of the first phosphahelicene with a terminal phosphinine ring was confirmed by X-ray crystallography.

Optimizing the Chemiluminescence of a Light-Producing Deoxyribozyme

Supernova is a chemiluminescent deoxyribozyme recently discovered in our group. It transfers the phosphate group from the 1,2-dioxetane substrate CDP-Star to its 5' hydroxyl group, which triggers a decomposition reaction and the production of light. Here we investigated the effects of reaction conditions on the ability of Supernova to generate a chemiluminescent signal (using a plate reader assay) and to phosphorylate itself (using a ligation assay). Our experiments indicate that multiple zinc ions are required for catalytic function, suggesting links between Supernova and protein enzymes that catalyze similar reactions. They also show how factors such as pH, potassium concentration, CDP-Star concentration, and DNA concentration affect the reaction. By combining information from different experiments, the rate enhancement of light production was increased by more than 1000-fold. These results should be useful for applications in which Supernova is used as a sensor.

Synthesis of Aza[n]helicenes (n = 4-7) via Photocyclodehydrochlorination of 1-Chloro-N-aryl-2-naphthamides

A series of aza[n]helicenes (n = 4-7) was synthesized using a photocyclodehydrochlorination of 1-chloro-N-aryl-2-naphthamides as a general synthetic procedure introducing the nitrogen atom to the third ring of the helicene framework. The effect of the nitrogen presence in the helicene skeleton on the physicochemical properties of the prepared aza[n]helicenes was studied and compared to those of the parent carbo-analogues. The insertion of a nitrogen atom into the outer edge of the helicene molecule has a severe impact on certain physicochemical properties such as optical rotation, electrostatic potentials, and intermolecular interactions. On the other hand, some other properties such as UV/vis, fluorescence, and phosphorescence spectra remained almost unaffected when compared to the parent carbohelicenes. A nitrogen atom can be also used for further derivatization, which can lead to further modification of helicene properties, as manifested here in the fluorescence changes induced by protonation.

Lulworthinone: In Vitro Mode of Action Investigation of an Antibacterial Dimeric Naphthopyrone Isolated from a Marine Fungus

Treatment options for infections caused by antimicrobial-resistant bacteria are rendered ineffective, and drug alternatives are needed—either from new chemical classes or drugs with new modes of action. Historically, natural products have been important contributors to drug discovery. In a recent study, the dimeric naphthopyrone lulworthinone produced by an obligate marine fungus in the family Lulworthiaceae was discovered. The observed potent antibacterial activity against Gram-positive bacteria, including several clinical methicillin-resistant Staphylococcus aureus (MRSA) isolates, prompted this follow-up mode of action investigation. This paper aimed to characterize the antibacterial mode of action (MOA) of lulworthinone by combining in vitro assays, NMR experiments and microscopy. The results point to a MOA targeting the bacterial membrane, leading to improper cell division. Treatment with lulworthinone induced an upregulation of genes responding to cell envelope stress in Bacillus subtilis. Analysis of the membrane integrity and membrane potential indicated that lulworthinone targets the bacterial membrane without destroying it. This was supported by NMR experiments using artificial lipid bilayers. Fluorescence microscopy revealed that lulworthinone affects cell morphology and impedes the localization of the cell division protein FtsZ. Surface plasmon resonance and dynamic light scattering assays showed that this activity is linked with the compound‘s ability to form colloidal aggregates. Antibacterial agents acting at cell membranes are of special interest, as the development of bacterial resistance to such compounds is deemed more difficult to occur.

The Effect of Deoxyfluorination on Intermolecular Interactions in the Crystal Structures of 1,6-Anhydro-2,3-epimino-hexopyranoses

The effect of substitution on intermolecular interactions was investigated in a series of 1,6-anhydro-2,3-epimino-hexopyranoses. The study focused on the qualitative evaluation of intermolecular interactions using DFT calculations and the comparison of molecular arrangements in the crystal lattice. Altogether, ten crystal structures were compared, including two structures of C4-deoxygenated, four C4-deoxyfluorinated and four parent epimino pyranoses. It was found that the substitution of the original hydroxy group by hydrogen or fluorine leads to a weakening of the intermolecular interaction by approximately 4 kcal/mol. The strength of the intermolecular interactions was found to be in the following descending order: hydrogen bonding of hydroxy groups, hydrogen bonding of the amino group, interactions with fluorine and weak electrostatic interactions. The intermolecular interactions that involved fluorine atom were rather weak; however, they were often supported by other weak interactions. The fluorine atom was not able to substitute the role of the hydroxy group in molecular packing and the fluorine atoms interacted only weakly with the hydrogen atoms located at electropositive regions of the carbohydrate molecules. However, the fluorine interaction was not restricted to a single molecule but was spread over at least three other molecules. This feature is a base for similar molecule arrangements in the structures of related compounds, as we found for the C4-F_ax and C4-F_eq epimines presented here.

Synthesis of Aza[n]phenacenes (n = 4-6) via Photocyclodehydrochlorination of 2-Chloro-N-aryl-1-naphthamides

A novel methodology for the synthesis of aza[n]phenacenes was successfully developed utilizing photocyclodehydrochlorination reaction of 2-chloro-N-aryl-1-naphthamides. In these key intermediates, the factors influencing the photoreaction were studied. The target aza[n]phenacenes were obtained by triflation or chlorination from prepared phenanthridinones, followed by hydrogenation. The introduction of a nitrogen atom into a phenacene skeleton induced changes in the physicochemical properties. The important properties of prepared aza[n]phenacenes (n = 4-6) were studied experimentally and by density functional theory calculations and were compared to those of their carbo analogues. Furthermore, some important features of the crystalline aza[n]phenacenes were investigated, including intermolecular interaction in the crystal lattice and the increased solubility or decreased melting points.

Supernova: A Deoxyribozyme that Catalyzes a Chemiluminescent Reaction

Functional DNA molecules are useful components in nanotechnology and synthetic biology. To expand the toolkit of functional DNA parts, in this study we used artificial evolution to identify a glowing deoxyribozyme called Supernova. This deoxyribozyme transfers a phosphate from a 1,2-dioxetane substrate to its 5' hydroxyl group, which triggers a chemiluminescent reaction and a flash of blue light. An engineered version of Supernova is only catalytically active in the presence of an oligonucleotide complementary to its 3' end, demonstrating that light production can be coupled to ligand binding. We anticipate that Supernova will be useful in a wide variety of applications, including as a signaling component in allosterically regulated sensors and in logic gates of molecular computers.

The biosynthesis of phospholipids is linked to the cell cycle in a model eukaryote

The structural challenges faced by eukaryotic cells through the cell cycle are key for understanding cell viability and proliferation. We tested the hypothesis that the biosynthesis of structural lipids is linked to the cell cycle. If true, this would suggest that the cell's structure is important for progress through and perhaps even control of the cell cycle. Lipidomics (31P NMR and MS), proteomics (Western immunoblotting) and transcriptomics (RT-qPCR) techniques were used to profile the lipid fraction and characterise aspects of its metabolism at seven stages of the cell cycle of the model eukaryote, Desmodesmus quadricauda. We found considerable, transient increases in the abundance of phosphatidylethanolamine during the G1 phase (+35%, ethanolamine phosphate cytidylyltransferase increased 2·5×) and phosphatidylglycerol (+100%, phosphatidylglycerol synthase increased 22×) over the G1/pre-replication phase boundary. The relative abundance of phosphatidylcholine fell by ~35% during the G1. N-Methyl transferases for the conversion of phosphatidylethanolamine into phosphatidylcholine were not found in the de novo transcriptome profile, though a choline phosphate transferase was found, suggesting that the Kennedy pathway is the principal route for the synthesis of PC. The fatty acid profiles of the four most abundant lipids suggested that these lipids were not generally converted between one another. This study shows for the first time that there are considerable changes in the biosynthesis of the three most abundant phospholipid classes in the normal cell cycle of D. quadricauda, by margins large enough to elicit changes to the physical properties of membranes.

Flavin-Helicene Amphiphilic Hybrids: Synthesis, Characterization, and Preparation of Surface-Supported Films

This work reports on the preparation and structural characterization of flavo[7]helicene 1 (flavin-[7]helicene conjugate), which was subsequently characterized at the molecular level in either an aqueous environment or an organic phase, at the supramolecular level in the form of polymeric layers, and also embedded in a lipidic mesophase environment to study the resulting properties of such a hybrid relative to its parent molecules. The flavin benzo[g]pteridin-2,4-dione (isoalloxazine) was selected for conjugation because of its photoactivity and reversible redox behavior. Compound 1 was prepared from 2-nitroso[6]helicene and 6-methylamino-3-methyluracil, and characterized using common structural and spectroscopic tools: circular dichroism (CD), circularly polarized luminescence (CPL) spectroscopy, cyclic voltammetry (CV), and DFT quantum calculations. In addition, a methodology that allows the loading of 1 enantiomers into an internally nanostructured lipid (1-monoolein) matrix was developed.

Cholesterol-containing lipid nanodiscs promote an α-synuclein binding mode that accelerates oligomerization

Dysregulation of the biosynthesis of cholesterol and other lipids has been implicated in many neurological diseases, including Parkinson's disease. Misfolding of α-synuclein (α-Syn), the main actor in Parkinson's disease, is associated with changes in a lipid environment. However, the exact molecular mechanisms underlying cholesterol effect on α-Syn binding to lipids as well as α-Syn oligomerization and fibrillation remain elusive, as does the relative importance of cholesterol compared to other factors. We probed the interactions and fibrillation behaviour of α-Syn using styrene-maleic acid nanodiscs, containing zwitterionic and anionic lipid model systems with and without cholesterol. Surface plasmon resonance and thioflavin T fluorescence assays were employed to monitor α-Syn binding, as well as fibrillation in the absence and presence of membrane models. 1 H-15 N-correlated NMR was used to monitor the fold of α-Syn in response to nanodisc binding, determining individual residue apparent affinities for the nanodisc-contained bilayers. The addition of cholesterol inhibited α-Syn interaction with lipid bilayers and, however, significantly promoted α-Syn fibrillation, with a more than a 20-fold reduction of lag times before fibrillation onset. When α-Syn bilayer interactions were analysed at an individual residue level by solution-state NMR, we observed two different effects of cholesterol. In nanodiscs made of DOPC, the addition of cholesterol modulated the NAC part of α-Syn, leading to stronger interaction of this region with the lipid bilayer. In contrast, in the nanodiscs comprising DOPC, DOPE and DOPG, the NAC part was mostly unaffected by the presence of cholesterol, while the binding of the N and the C termini was both inhibited.

Recent Advances in Functionalizations of Helicene Backbone

Helicenes, chiral members of the family of polyaromatic hydrocarbons, have been increasingly used in a variety of applications in recent years. Despite their intriguing properties, wider utilization is hindered by difficult functionalization of its skeleton, which would provide access to finely tuned derivatives of desired properties. Herein, the recent advancements in the field of helicene functionalization are discussed with an emphasis on different types of transformations, their versatility, and regioselectivity.

Plasma-derived exosome-like vesicles are enriched in lyso-phospholipids and pass the blood-brain barrier

Exosomes are vesicles involved in intercellular communication. Their membrane structure and core content is largely dependent on the cell of origin. Exosomes have been investigated both for their biological roles and their possible use as disease biomarkers and drug carriers. These potential technological applications require the rigorous characterization of exosomal blood brain barrier permeability and a description of their lipid bilayer composition. To achieve these goals, we have established a 3D static blood brain barrier system based on existing systems for liposomes and a complementary LC-MS/MS and ³¹P nuclear magnetic resonance methodology for the analysis of purified human plasma-derived exosome-like vesicles. Results show that the isolated vesicles pass the blood brain barrier and are taken up in endothelial cells. The compositional analysis revealed that the isolated vesicles are enriched in lyso phospholipids and do not contain phosphatidylserine. These findings deviate significantly from the composition of exosomes originating from cell culture, and may reflect active removal by macrophages that respond to exposed phosphahtidylserine.

Bioactive Metabolites of Marine Origin Have Unusual Effects on Model Membrane Systems

Marine sponges and soft corals have yielded novel compounds with antineoplastic and antimicrobial activities. Their mechanisms of action are poorly understood, and in most cases, little relevant experimental evidence is available on this topic. In the present study, we investigated whether agelasine D (compound 1) and three agelasine analogs (compound 2–4) as well as malonganenone J (compound 5), affect the physical properties of a simple lipid model system, consisting of dioleoylphospahtidylcholine and dioleoylphosphatidylethanolamine. The data indicated that all the tested compounds increased stored curvature elastic stress, and therefore, tend to deform the bilayer which occurs without a reduction in the packing stress of the hexagonal phase. Furthermore, lower concentrations (1%) appear to have a more pronounced effect than higher ones (5–10%). For compounds 4 and 5, this effect is also reflected in phospholipid headgroup mobility assessed using ³¹P chemical shift anisotropy (CSA) values of the lamellar phases. Among the compounds tested, compound 4 stands out with respect to its effects on the membrane model systems, which matches its efficacy against a broad spectrum of pathogens. Future work that aims to increase the pharmacological usefulness of these compounds could benefit from taking into account the compound effects on the fluid lamellar phase at low concentrations.

Photochemical Functionalization of Helicenes

Herein, a visible-light photochemical approach for practical helicene functionalization at very mild reaction conditions is described. The photochemical reactions allow for the regiospecific and innate late-stage functionalization of helicenes and are easily executed either through the activation of C(sp2 )-Br bonds in helicenes using K2 CO3 as inorganic base or direct C(sp2 )-H helicene bond functionalization under oxidative photoredox reaction conditions. Overall, using these transformations six different functional groups are introduced to the helicene scaffold through C-C and four different C-heteroatom bond-forming reactions.

Fast and Quantitative Phospholipidomic Analysis of SH-SY5Y Neuroblastoma Cell Cultures Using Liquid Chromatography-Tandem Mass Spectrometry and 31P Nuclear Magnetic Resonance

Global lipid analysis still lags behind proteomics with respect to the availability of databases, experimental protocols, and specialized software. Determining the lipidome of cellular model systems in common use is of particular importance, especially when research questions involve lipids directly. In Parkinson's disease research, there is a growing awareness for the role of the biological membrane, where individual lipids may contribute to provoking α-synuclein oligomerisation and fibrillation. We present an analysis of the whole cell and plasma membrane lipid isolates of a neuroblastoma cell line, SH-SY5Y, a commonly used model system for research on this and other neurodegenerative diseases. We have used two complementary lipidomics methods. The relative quantities of PC, PE, SMs, CL, PI, PG, and PS were determined by ³¹P NMR. Fatty acid chain composition and their relative abundances within each phospholipid group were evaluated by liquid chromatography-tandem mass spectrometry. For this part of the analysis, we have developed and made available a set of Matlab scripts, LipMat. Our approach allowed us to observe several deviations of lipid abundances when compared to published reports regarding phospholipid analysis of cell cultures or brain matter. The most striking was the high abundance of PC (54.7 ± 1.9%) and low abundance of PE (17.8 ± 4.8%) and SMs (2.7 ± 1.2%). In addition, the observed abundance of PS was smaller than expected (4.7 ± 2.7%), similar to the observed abundance of PG (4.5 ± 1.8%). The observed fatty acid chain distribution was similar to the whole brain content with some notable differences: a higher abundance of 16:1 PC FA (17.4 ± 3.4% in PC whole cell content), lower abundance of 22:6 PE FA (15.9 ± 2.2% in plasma membrane fraction), and a complete lack of 22:6 PS FA.

Microgel Bioreactors for Cancer Cell Targeting by pH-Dependent Generation of Radicals

The lack of specificity of traditional cytostatics and increasing resistance of cancer cells represent important challenges in cancer therapy. One of the characteristics of cancer cells is their intrinsic oxidative stress caused by higher metabolic activity, mitochondrial malfunction, and oncogene stimulation. This feature can be exploited in the pursuit of more selective cancer therapy, as there is increasing evidence that cancer cells are more sensitive to elevated concentrations of reactive oxygen species than normal cells. In this study, we demonstrate a new concept for cancer cell targeting by in situ production of radicals under physiological conditions. The biologically active radicals are produced in the milieu of cancer cells by enzymatic conversion from an inactive precursor, 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)diammonium salt, by using miniature bioreactors represented by cell-sized microgels containing immobilized laccase. We utilize the pH-dependent activity of laccase to generate radicals only at a lower pH (5.7-6.1) that is characteristic of the tumor microenvironment. The composition of the microgels was optimized so as to allow sufficient substrate and radical diffusion, high enzyme activity, and stability under physiological conditions. The functionality of this system was evaluated on three cancer cell lines (HeLa, HT-29, and DLD1) and the cytotoxicity of in situ-produced radicals was successfully proven in all cases. These results demonstrate that cancer cell targeting by in situ-generated radicals using miniature enzymatic reactors may represent an alternative to traditional cytostatics. In particular, the pH-dependence of radical generation and their short-lived nature can ensure localized functionality in the tumor microenvironment and thereby reduce systemic side-effects.

Enantioselective complexation of 1-phenylethanol with chiral compounds bearing urea moiety

A detailed study of diastereomeric complexes of chiral ureido-1,1'-binaphthalene derivatives with chiral 1-phenylethanol showed that a derivative bearing only one urea unit makes five times more stable complex with (S)-enantiomer than with (R)-enantiomer of the alcohol. This phenomenon could be used in chiral discrimination processes. The influence of individual parts of the structure on the complexation properties is shown. The probable structure of diastereomeric complexes based on experimental results and computational methods is proposed.

2-Bromo[6]helicene as a Key Intermediate for [6]Helicene Functionalization

The synthesis of 2-bromo[6]helicene was revised and improved up to 51% yield. Its reactivity was thoroughly investigated, and a library of 17 different carbon, boron, nitrogen, phosphorus, oxygen and sulfur substituted derivatives was prepared. The racemization barrier for 2-bromo[6]helicene was determined, and the usage of enantiomers in the synthesis of optically pure helicenes was rationalized. The three most energy-demanding reactions using enantiomerically pure 2-bromo[6]helicene were tested in order to confirm the predicted enantiomeric excess.

Evidence that Listeria innocua modulates its membrane's stored curvature elastic stress, but not fluidity, through the cell cycle

This paper reports that the abundances of endogenous cardiolipin and phosphatidylethanolamine halve during elongation of the Gram-positive bacterium Listeria innocua. The lyotropic phase behaviour of model lipid systems that describe these modulations in lipid composition indicate that the average stored curvature elastic stress of the membrane is reduced on elongation of the cell, while the fluidity appears to be maintained. These findings suggest that phospholipid metabolism is linked to the cell cycle and that changes in membrane composition can facilitate passage to the succeding stage of the cell cycle. This therefore suggests a means by which bacteria can manage the physical properties of their membranes through the cell cycle.

Detection of misfolded protein aggregates from a clinical perspective

Neurodegenerative Protein Misfolding Diseases (PMDs), such as Alzheimer's (AD), Parkinson's (PD) and prion diseases, are generally difficult to diagnose before irreversible damage to the central nervous system damage has occurred. Detection of the misfolded proteins that ultimately lead to these conditions offers a means for providing early detection and diagnosis of this class of disease. In this review, we discuss recent developments surrounding protein misfolding diseases with emphasis on the cytotoxic oligomers implicated in their aetiology. We also discuss the relationship of misfolded proteins with biological membranes. Finally, we discuss how far techniques for providing early diagnoses for PMDs have advanced and describe promising clinical approaches. We conclude that antibodies with specificity towards oligomeric species of AD and PD and lectins with specificity for particular glycosylation, show promise. However, it is not clear which approach may yield a reliable clinical test first. Relevance for patients: Individuals suffering from protein misfolding diseases will likely benefit form earlier, less- or even non-invasive diagnosis techniques. The current state and possible future directions for these are subject of this review.

A novel flotation technique for the separation of nonadherent micro-organisms from a substrate

An understanding of adherence ability is crucial in many areas, for example, in research on biofilms, evaluation of probiotics or in biotechnology. In all these analyses, the reproducible washing is very important in the prevention of false results. During washing, the force, direction of the flow, position of the pipette tip, number of washing cycles, type of washing solution and the way of removing the washing solution can be sources of inappropriate stress to attached cells. To overcome these problems, we here propose the use of high mass density solutions as flotation agents. As the density of bacteria is lower than that of the flotation solutions, nonattached or weakly attached bacteria are moved to the surface due to hydrostatic force. Caesium chloride, ammonium nitrate and sodium diatrizoate solutions, which are commonly used as FAs, were compared with a standard method of rinsing. Several concentrations of agents were used to investigate the optimal concentration and influence of hydrostatic pressure on adhered micro-organisms. We show that flotation is a rapid method for distinguishing between adhered and weakly attached or loosed cells with reproducible results. Due to its range of possible mass density concentration, the best FA was shown to be caesium chloride.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first study that suggests using flotation agents to separate planktonic from adhered bacteria. When a high-density solution is used, buoyancy of bacteria ensures their segregation in the solution. Flotation agents could be used instead of washing procedure, which is inaccurate and hardly reproducible. High-density flotation agents could be used for more precise evaluation of bacterial adherence in many assays, such as research of biofilms or evaluation of probiotics.