In Vitro Biocompatibility and Endothelial Permeability of Branched Polyglycidols Generated by Ring-Opening Polymerization of Glycidol with B(C6F5)3 under Dry and Wet Conditions

Polyglycidol or polyglycerol (PG), a polyether widely used in biomedical applications, has not been extensively studied in its branched cyclic form (bcPG), despite extensive research on hyperbranched PG (HPG). This study explores the biomedical promise of bcPG, particularly its ability to cross the blood-brain barrier (BBB). We evaluate in vitro biocompatibility, endothelial permeability, and formation of branched linear PG (blPG) as topological impurities in the presence of water. Small angle X-ray scattering in solution revealed a fractal dimension of approximately two for bcPG and the mixture bc+blPG, suggesting random branching. Comparisons of cytotoxicity and endothelial permeability between bcPG, bc+blPG, and HPG in a BBB model using hCMEC/D3 cells showed different biocompatibility profiles and higher endothelial permeability for HPG. bcPG showed a tendency to accumulate around cell nuclei, in contrast to the behavior of HPG. This study contributes to the understanding of the influence of polymer topology on biological behavior.

A poly-proline II helix in YadA from Yersinia enterocolitica serotype O:9 facilitates heparin binding through electrostatic interactions

Poly-proline II helices are secondary structure motifs frequently found in ligand-binding sites. They exhibit increased flexibility and solvent exposure compared to the strongly hydrogen-bonded α-helices or β-strands and can therefore easily be misinterpreted as completely unstructured regions with an extremely high rotational freedom. Here, we show that the adhesin YadA of Yersinia enterocolitica serotype O:9 contains a poly-proline II helix interaction motif in the N-terminal region. The motif is involved in the interaction of YadAO:9 with heparin, a host glycosaminoglycan. We show that the basic residues within the N-terminal motif of YadA are required for electrostatic interactions with the sulfate groups of heparin. Biophysical methods including CD spectroscopy, solution-state NMR and SAXS all independently support the presence of a poly-proline helix allowing YadAO:9 binding to the rigid heparin. Lastly, we show that host cells deficient in sulfation of heparin and heparan sulfate are not targeted by YadAO:9 -mediated adhesion. We speculate that the YadAO:9 -heparin interaction plays an important and highly strain-specific role in the pathogenicity of Yersinia enterocolitica serotype O:9.

Accelerating Lipid Flip-Flop at Low Concentrations: A General Mechanism for Membrane Binding Peptides

We report a physicochemical investigation of the lipid transport properties of model lipid membranes in the presence of the antimicrobial peptide indolicidin through comparisons of experimental SANS/SAXS scattering techniques to fully atomistic molecular dynamics simulations. In agreement with the experiment, we show that upon peripheral binding of the peptides, even at low concentrations, lipid flip-flop dynamics is greatly accelerated. Computer modeling elucidates the interplay between structural changes and lipid dynamics induced by peptides and proposes a mechanism for the mode of action of antimicrobial peptides, assessing the major role of entropy for the catalysis of the flipping events. The mechanism introduced here is universal for all peptides with preferential peripheral binding to the membrane as it does not depend on the specific amino acid sequence.

Real-Time Monitoring of Multitarget Antimicrobial Mechanisms of Peptoids Using Label-Free Imaging with Optical Diffraction Tomography

Antimicrobial peptides (AMPs) are promising therapeutics in the fight against multidrug-resistant bacteria. As a mimic of AMPs, peptoids with N-substituted glycine backbone have been utilized for antimicrobials with resistance against proteolytic degradation. Antimicrobial peptoids are known to kill bacteria by membrane disruption; however, the nonspecific aggregation of intracellular contents is also suggested as an important bactericidal mechanism. Here,structure-activity relationship (SAR) of a library of indole side chain-containing peptoids resulting in peptoid 29 as a hit compound is investigated. Then, quantitative morphological analyses of live bacteria treated with AMPs and peptoid 29 in a label-free manner using optical diffraction tomography (ODT) are performed. It is unambiguously demonstrated that both membrane disruption and intracellular biomass flocculation are primary mechanisms of bacterial killing by monitoring real-time morphological changes of bacteria. These multitarget mechanisms and rapid action can be a merit for the discovery of a resistance-breaking novel antibiotic drug.

Stability of Nanopeptides: Structure and Molecular Exchange of Self-assembled Peptide Fibers

Often nanostructures formed by self-assembly of small molecules based on hydrophobic interactions are rather unstable, causing morphological changes or even dissolution when exposed to changes in aqueous media. In contrast, peptides offer precise control of the nanostructure through a range of molecular interactions where physical stability can be engineered in and, to a certain extent, decoupled from size via rational design. Here, we investigate a family of peptides that form beta-sheet nanofibers and demonstrate a remarkable physical stability even after attachment of poly(ethylene glycol). We employed small-angle neutron/X-ray scattering, circular dichroism spectroscopy, and molecular dynamics simulation techniques to investigate the detailed nanostructure, stability, and molecular exchange. The results for the most stable sequence did not reveal any structural alterations or unimer exchange for temperatures up to 85 °C in the biologically relevant pH range. Only under severe mechanical perturbation (i.e., tip sonication) would the fibers break up, which is reflected in a very high activation barrier for unimer exchange of ∼320 kJ/mol extracted from simulations. The results give important insight into the relation between molecular structure and stability of peptide nanostructure that is important for, e.g., biomedical applications.

Micelle kinetics of photoswitchable surfactants: Self-assembly pathways and relaxation mechanisms

HYPOTHESIS

A key question in the kinetics of surfactant self-assembly is whether exchange of unimers or fusion/fission of entire micelles is the dominant pathway. In this study, an isomerizable surfactant is used to explore fundamental out-of-equilibrium kinetics and mechanisms for growth and dissolution of micelles.

EXPERIMENTS

The kinetics of cationic surfactant 4-butyl-4'-(3-trimethylammoniumpropoxy)-phenylazobenzene was studied using molecular dynamics simulations. The fusion and exchange processes were investigated using umbrella sampling. Equilibrium states were validated by comparison with small-angle X-ray scattering data. The photo-isomerization event was simulated by modifying the torsion potential of the photo-responsive group to emulate the trans-to-cis transition.

FINDINGS

Micelle growth is dominated by unimer exchange processes, whereas, depending on the conditions, dissolution can occur both through fission and unimer expulsion. Fusion barriers increase steeply with the aggregation number making this an unlikely pathway to equilibrium for micelles of sizes that fit with the experimental data. The barriers for unimer expulsion remain constant and are much lower for unimer insertion, making exchange more likely at high aggregation. When simulating photo-conversion events, both fission and a large degree of unimer expulsion can occur depending on the extent of the out-of-equilibrium stress that is put on the system.

Pathways of Membrane Solubilization: A Structural Study of Model Lipid Vesicles Exposed to Classical Detergents

Understanding the pathways of solubilization of lipid membranes is of high importance for their use in biotechnology and industrial applications. Although lipid vesicle solubilization by classical detergents has been widely investigated, there are few systematic structural and kinetic studies where different detergents are compared under varying conditions. This study used small-angle X-ray scattering to determine the structures of lipid/detergent aggregates at different ratios and temperatures and studied the solubilization in time using the stopped-flow technique. Membranes composed of either of two zwitterionic lipids, DMPC or DPPC, and their interactions with three different detergents, sodium dodecyl sulfate (SDS), n-dodecyl-beta-maltoside (DDM), and Triton X-100 (TX-100), were tested. The detergent TX-100 can cause the formation of collapsed vesicles with a rippled bilayer structure that is highly resistant to TX-100 insertion at low temperatures, while at higher temperatures, it partitions and leads to the restructuring of vesicles. DDM also causes this restructuring into multilamellar structures at subsolubilizing concentrations. In contrast, partitioning of SDS does not alter the vesicle structure below the saturation limit. Solubilization is more efficient in the gel phase for TX-100 but only if the cohesive energy of the bilayer does not prevent sufficient partitioning of the detergent. DDM and SDS show less temperature dependence compared to TX-100. Kinetic measurements reveal that solubilization of DPPC largely occurs through a slow extraction of lipids, whereas DMPC solubilization is dominated by fast and burst-like solubilization of the vesicles. The final structures obtained seem to preferentially be discoidal micelles where the detergent can distribute in excess along the rim of the disc, although we do observe the formation of worm- and rodlike micelles in the case of solubilization of DDM. Our results are in line with the suggested theory that bilayer rigidity is the main factor influencing which aggregate is formed.

Beyond the standard model of solubilization: Non-ionic surfactants induce collapse of lipid vesicles into rippled bilamellar nanodiscs

HYPOTHESIS

Although solubilization of lipid membranes has been studied extensively, questions remain regarding the structural pathways and metastable structures involved. This study investigated whether the non-ionic detergent Triton X-100 follows the classical solubilization pathway or if intermediate nanostructures are formed.

EXPERIMENTS

Small angle X-ray and neutron scattering (SAXS/SANS) was used in combination with transmission electron cryo-microscopy and cryo-tomography to deduce the structure of mixtures of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) vesicles and Triton X-100. Time-resolved SAXS and dynamic light scattering were used to investigate the kinetics of the process.

FINDINGS

Upon addition of moderate detergent amounts at low temperatures, the lipid vesicles implode into ordered rippled bilamellar disc structures. The bilayers arrange in a ripple phase to accommodate packing constraints caused by inserted TX-100 molecules. The collapse is suggested to occur through a combination of water structure destabilization by detergents flipping across the membrane and osmotic pressure causing interbilayer attraction internally. The subsequently induced ripples then stabilize the aggregates and prevent solubilization, supported by the observation that negatively charged vesicles undergo a different pathway upon TX-100 addition, forming large bicelles. The findings demonstrate the richness in assembly pathways of simple lipids and detergents and stimulate considerations for the use of certain detergents in membrane solubilization.

A trimeric coiled-coil motif binds bacterial lipopolysaccharides with picomolar affinity

α-helical coiled-coils are ubiquitous protein structures in all living organisms. For decades, modified coiled-coils sequences have been used in biotechnology, vaccine development, and biochemical research to induce protein oligomerization, and form self-assembled protein scaffolds. A prominent model for the versatility of coiled-coil sequences is a peptide derived from the yeast transcription factor, GCN4. In this work, we show that its trimeric variant, GCN4-pII, binds bacterial lipopolysaccharides (LPS) from different bacterial species with picomolar affinity. LPS molecules are highly immunogenic, toxic glycolipids that comprise the outer leaflet of the outer membrane of Gram-negative bacteria. Using scattering techniques and electron microscopy, we show how GCN4-pII breaks down LPS micelles in solution. Our findings suggest that the GCN4-pII peptide and derivatives thereof could be used for novel LPS detection and removal solutions with high relevance to the production and quality control of biopharmaceuticals and other biomedical products, where even minuscule amounts of residual LPS can be lethal.

The association of loneliness and social isolation with healthcare utilization in Denmark

Objectives

The present prospective cohort study investigated the association of loneliness and social isolation (SI) with healthcare utilization (HCU) in the general population over time.

Methods

Data from the 2013 Danish “How are you?’ survey (n = 29,472) were combined with individual-level register data from the National Danish Patient Registry and the Danish National Health Service Registry over a 6-year follow-up period (2013-2018). Negative binomial regression analyses were performed while adjusting for baseline demographics and chronic disease.

Results

Loneliness measured at baseline was significantly associated with more GP contacts (incident-rate ratio (IRR) = 1.03, 95% confidence interval (CI) [1.02, 1.04]), more emergency treatments (IRR = 1.06, 95% CI [1.03, 1.10]), more emergency admissions (IRR = 1.06, 95% CI [1.03, 1.06]), and hospital admission days (IRR=1.05, 95% CI [1.00, 1.11]) across the 6-year follow-up period. No significant associations were found between social isolation and HCU with one minor exception, in which SI was associated with fewer planned outpatient treatments (IRR = .97, 95% CI [.94, .99]).

Conclusions

Our findings suggest that loneliness is a risk factor for certain types of HCU, independent of social isolation, baseline demographics, and chronic disease.

Key messages

Self-Assembly of Antimicrobial Peptoids Impacts Their Biological Effects on ESKAPE Bacterial Pathogens

Antimicrobial peptides (AMPs) are promising pharmaceutical candidates for the prevention and treatment of infections caused by multidrug-resistant ESKAPE pathogens, which are responsible for the majority of hospital-acquired infections. Clinical translation of AMPs has been limited, in part by apparent toxicity on systemic dosing and by instability arising from susceptibility to proteolysis. Peptoids (sequence-specific oligo-N-substituted glycines) resist proteolytic digestion and thus are of value as AMP mimics. Only a few natural AMPs such as LL-37 and polymyxin self-assemble in solution; whether antimicrobial peptoids mimic these properties has been unknown. Here, we examine the antibacterial efficacy and dynamic self-assembly in aqueous media of eight peptoid mimics of cationic AMPs designed to self-assemble and two nonassembling controls. These amphipathic peptoids self-assembled in different ways, as determined by small-angle X-ray scattering; some adopt helical bundles, while others form core-shell ellipsoidal or worm-like micelles. Interestingly, many of these peptoid assemblies show promising antibacterial, antibiofilm activity in vitro in media, under host-mimicking conditions and antiabscess activity in vivo. While self-assembly correlated overall with antibacterial efficacy, this correlation was imperfect. Certain self-assembled morphologies seem better-suited for antibacterial activity. In particular, a peptoid exhibiting a high fraction of long, worm-like micelles showed reduced antibacterial, antibiofilm, and antiabscess activity against ESKAPE pathogens compared with peptoids that form ellipsoidal or bundled assemblies. This is the first report of self-assembling peptoid antibacterials with activity against in vivo biofilm-like infections relevant to clinical medicine.

Molecular Transport and Growth of Lipid Vesicles Exposed to Antimicrobial Peptides

It is well-known that lipids constituting the cytoplasmic membrane undergo continuous reorganization to maintain the appropriate composition important for the integrity of the cell. The transport of lipids is controlled by mainly membrane proteins, but also spontaneous lipid transport between leaflets, lipid "flip-flop", occurs. These processes do not only occur spontaneously under equilibrium, but also promote structural rearrangements, morphological transitions, and growth processes. It has previously been shown that intravesicular lipid "flip-flop" and intervesicular lipid exchange under equilibrium can be deduced indirectly from contrast variation time-resolved small-angle neutron scattering (TR-SANS) where the molecules are "tagged" using hydrogen/deuterium (H/D) substitution. In this work, we show that this technique can be extended to simultaneously detect changes in the growth and the lipid "flip-flop" and exchange rates induced by a peptide additive on lipid vesicles consisting of DMPC (1,2-dimyristoyl-sn-glycero-3-phosphocholine), d-DMPC (1,2-dimyristoyl-d54-sn-glycero-3-phosphocholine), DMPG (1,2-dimyristoyl-sn-glycero-3-phospho-(1'-rac-glycerol)), and small amounts of DMPE-PEG (1,2-dimyristoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000]). Changes in the overall size were independently monitored using dynamic light scattering (DLS). We find that the antimicrobial peptide, indolicidin, accelerates lipid transport and additionally induces limited vesicular growth. Moreover, in TR-SANS experiments using partially labeled lipid mixtures to separately study the kinetics of the lipid components, we show that, whereas peptide addition affects both lipids similarly, DMPG exhibits faster kinetics. We find that vesicular growth is mainly associated with peptide-mediated lipid reorganization that only slightly affects the overall exchange kinetics. This is confirmed by a TR-SANS experiment of vesicles preincubated with peptide showing that after pre-equilibration the kinetics are only slightly slower.

Transition kinetics of mixed lipid:photosurfactant assemblies studied by time-resolved small angle X-ray scattering

HYPOTHESIS

Photoswitchable surfactants are used in the design of many light-responsive colloids and/or self-assemblies. Photo-isomerization enables to control molecular equilibrium, and triggers transient reorganizations with possibly out-of-equilibrium intermediate states that have been overlooked. Here, we address this question by an in depth structural investigation of intermediate lipid-surfactant assemblies that occur during fast isothermal photo-triggered transition in lipid:surfactant mixtures.

EXPERIMENTS

The structural parameters of mixed assemblies of azobenzene-containing cationic surfactant (AzoTMA) and dioleoylphosphatidylcholine (DOPC) lipids were studied by light scattering and time-resolved small angle X-ray scattering. Structural and compositional information about the assemblies and unimers in bulk were determined at the photostationary states, as well as at intermediate kinetic states formed during UV or blue light illumination.

FINDINGS

DOPC:AzoTMA systems form mixed assemblies representative of phospholipid:cationic surfactant mixtures, that evolve from spheroid, to rod-like micelles, and vesicles with increasing DOPC fraction. Transient assemblies detected during the photo-triggered kinetics are similar to the ones found in stationary states. But changes of AzoTMA unimers in bulk can be considerably faster than mass reorganizations of the mixed assemblies, suggesting that out-of-equilibrium conditions are transiently reached. Mass reorganization of the surfactant-enriched assemblies is much faster than in the lipid enriched ones, providing insight into the role of lipids in a slow reorganization of the assemblies.

Lifecourse partnership breakups or years lived alone and low grade inflammation in middle-aged adults

Background

Divorce and living alone are associated with several adverse health outcomes. There is however very limited knowledge on the potential effects of exposure across the life course. The aim of this study is to investigate whether accumulated number of divorces/partnership breakups or years lived alone across 26 years of adult life, is associated with levels of low grade inflammation and if vulnerability with regards to gender or educational level can be identified.

Methods

4,835 participants from Copenhagen Aging and Midlife Biobank (CAMB) aged 48-62 were included. Accumulated number of partnership breakups and years living alone, were retrieved from a national standardized annual register. Inflammatory markers, Interleukin-6 (IL-6) and high sensitivity C-Reactive Protein (hsCRP), were measured in plasma samples. Multivariate linear regression analyses were adjusted for age, educational level, early major life events, BMI, chronic diseases, medicinal intake that affects inflammation, acute inflammation, and personality scores (neuroticism, agreeableness, conscientiousness).

Results

For men, two or more partnership breakups as well as living alone for 7+ years was associated with significantly higher levels of and inflammatory markers, i.e. 12-17% higher level of hsCRP and IL6 compared to the reference groups (no break-ups/0-1 years living alone) p-values <0.0001-0.024. No associations were found for women, and no joint effect of partnership breakups and educational level was found for either gender.

Conclusions

The findings suggest a strong association between accumulated number of partnership breakups or years lived alone across 26 year of adult life and low grade inflammation for middle-aged men but not for women. No specific vulnerability among the lower was identified. The findings points towards the importance of developing tailored preventive initiatives to males experiencing several partner-break-ups or who lives alone for many years.

Key messages

Two or more partnership breakups or 7+ years lived alone across 26 year of adult life is associated with increased low grade inflammation for middle-aged men but not for women. No increased vulnerability among the low educated was identified.

Associations of loneliness and social isolation with physical and mental health among adolescents and young adults

AIMS

The present study investigates whether loneliness and social isolation are associated with poor physical and mental health among adolescents and young adults, and whether age and gender play a role in the associations of loneliness and social isolation with mental and physical health.

METHODS

This study used cross-sectional self-report data from the 2017 Danish Health and Morbidity Surveys titled 'How are you?' (N = 19,890, M = 22.6 years).

RESULTS

Logistic regression analyses showed that loneliness and social isolation were independently associated with poor physical and mental health. Loneliness was associated with increased odds of asthma, migraine, osteoarthritis, rheumatoid arthritis, hypertension, slipped disc/back pain, tinnitus, long-term mental illness, depressive symptomatology, anxiety symptomatology and alcohol problems. Social isolation was associated with decreased odds of having migraine, osteoarthritis and alcohol problems, and an increased risk of long-term mental illness and depressive symptomatology. Small age and gender differences were detected.

CONCLUSIONS

In adolescents and young adults, loneliness and social isolation were associated with poor mental health and loneliness with poor physical health. These findings highlight the need for targeted prevention and intervention initiatives to alleviate loneliness and social isolation.

Understanding the Structural Pathways for Lipid Nanodisc Formation: How Styrene Maleic Acid Copolymers Induce Membrane Fracture and Disc Formation

Lipid nanodiscs formed by mixtures of styrene maleic acid (SMA) copolymers and lipid membranes are important tools for studying membrane proteins in many biotechnological applications. However, molecular interactions leading up to their formation are not well understood. Here, we elucidate the nanodisc formation pathways for SMA/lipid vesicle mixtures using small-angle X-ray scattering (SAXS) that allows detailed in situ nanostructural information. SMA copolymer that is initially aggregated in solution inserts its styrene units into the lipid bilayer hydrocarbon region, leading to fractures in the membrane. The initial copolymer-lipid interactions observed in the vesicles are also present in the formed discs, with excess copolymer distributed along the normal of the bilayer. The size and SMA distribution in the resulting discs strongly depend on the temperature, lipid/copolymer ratio, and lipid type. We find that the solubilization limit increases for membranes above the melting point, suggesting that defects in gel-like lipid membranes play a significant role in membrane fracturing and nanodisc formation. These findings provide unique insights into the formation of nanodiscs as well as into the microscopic mechanism of solubilization, which plays an important role in many applications and products ranging from household goods to biotechnology and medicine.

Impact of antimicrobial peptides on E. coli-mimicking lipid model membranes: correlating structural and dynamic effects using scattering methods

Using X-rays and neutrons we address the effect of AMPs on structure and dynamics of lipids in bacterial model membranes.

Spherical Micelles with Nonspherical Cores: Effect of Chain Packing on the Micellar Shape

Self-assembly of amphiphilic polymers into micelles is an archetypical example of a "self-confined" system due to the formation of micellar cores with dimensions of a few nanometers. In this work, we investigate the chain packing and resulting shape of C n -PEOx micelles with semicrystalline cores using small/wide-angle X-ray scattering (SAXS/WAXS), contrast-variation small-angle neutron scattering (SANS), and nuclear magnetic resonance spectroscopy (NMR). Interestingly, the n-alkyl chains adopt a rotator-like conformation and pack into prolate ellipses (axial ratio ϵ ≈ 0.5) in the "crystalline" region and abruptly arrange into a more spheroidal shape (ϵ ≈ 0.7) above the melting point. We attribute the distorted spherical shape above the melting point to thermal fluctuations and intrinsic rigidity of the n-alkyl blocks. We also find evidence for a thin dehydrated PEO layer (≤1 nm) close to the micellar core. The results provide substantial insight into the interplay between crystallinity and molecular packing in confinement and the resulting overall micellar shape.

How Detergents Dissolve Polymeric Micelles: Kinetic Pathways of Hybrid Micelle Formation in SDS and Block Copolymer Mixtures

Mixtures of amphiphilic polymers and surfactants are used in a wide range of applications, e.g., pharmaceuticals, detergents, cosmetics, and drug delivery systems. Still, many questions remain on how the structure and, in particular, the kinetics of block copolymer micelles are affected in the presence of surfactants and what controls the solubilization kinetics. In this work, we have studied the stability and solubilization kinetics of block copolymer micelles upon the addition of the surfactant sodium dodecyl sulfate (SDS) using small-angle X-ray/neutron scattering. The ability of the surfactant to dissolve polymer micelles or form mixed micelles has been investigated using two types of amphiphilic polymers, poly(ethylene-alt-propylene)-poly(ethylene oxide) (PEP1-PEO20) and n-alkyl-functionalized PEO (C28-PEO5). The exchange kinetics of C28-PEO5 micelles are in the order of hours, while PEP1-PEO20 micelles are known to be frozen on a practical timescale. In this work, we show that the addition of SDS to PEP1-PEO20 provides virtually no solubilization, even after an extended period of time. However, upon adding SDS to C28-PEO5 micelles, we observe micellar dissolution and formation of mixed micelles occurring on the timescale of hours. Using a coexistence model of mixed and neat micelles, the SAXS data were analyzed to provide detailed structural parameters over time. First, we observe a fast fragmentation/fission step followed by a slow reorganization process. The latter process is essentially independent of concentration at low volume fraction but is greatly accelerated at larger concentrations. This might indicate a crossover from a predominance of molecular exchange to fusion/fission processes.

Supramolecular Packing Drives Morphological Transitions of Charged Surfactant Micelles

The shape and size of self-assembled structures upon local organization of their molecular building blocks are hard to predict in the presence of long-range interactions. Combining small-angle X-ray/neutron scattering data, theoretical modelling, and computer simulations, sodium dodecyl sulfate (SDS), over a broad range of concentrations and ionic strengths, was investigated. Computer simulations indicate that micellar shape changes are associated with different binding of the counterions. By employing a toy model based on point charges on a surface, and comparing it to experiments and simulations, it is demonstrated that the observed morphological changes are caused by symmetry breaking of the irreducible building blocks, with the formation of transient surfactant dimers mediated by the counterions that promote the stabilization of cylindrical instead of spherical micelles. The present model is of general applicability and can be extended to all systems controlled by the presence of mobile charges.

Helicity Modulation Improves the Selectivity of Antimicrobial Peptoids

The modulation of conformational flexibility in antimicrobial peptides (AMPs) has been investigated as a strategy to improve their efficacy against bacterial pathogens while reducing their toxicity. Here, we synthesized a library of helicity-modulated antimicrobial peptoids by the position-specific incorporation of helix-inducing monomers. The peptoids displayed minimal variations in hydrophobicity, which permitted the specific assessment of the effect of conformational differences on antimicrobial activity and selectivity. Among the moderately helical peptoids, the most dramatic increase in selectivity was observed in peptoid 17, providing more than a 20-fold increase compared to fully helical peptoid 1. Peptoid 17 had potent broad-spectrum antimicrobial activity that included clinically isolated multi-drug-resistant pathogens. Compared to pexiganan AMP, 17 showed superior metabolic stability, which could potentially reduce the dosage needed, alleviating toxicity. Dye-uptake assays and high-resolution imaging revealed that the antimicrobial activity of 17 was, as with many AMPs, mainly due to membrane disruption. However, the high selectivity of 17 reflected its unique conformational characteristics, with differential interactions between bacterial and erythrocyte membranes. Our results suggest a way to distinguish different membrane compositions solely by helicity modulation, thereby improving the selectivity toward bacterial cells with the maintenance of potent and broad-spectrum activity.

Lipid membrane interactions of self-assembling antimicrobial nanofibers: effect of PEGylation

Supramolecular assembly and PEGylation (attachment of a polyethylene glycol polymer chain) of peptides can be an effective strategy to develop antimicrobial peptides with increased stability, antimicrobial efficacy and hemocompatibility. However, how the self-assembly properties and PEGylation affect their lipid membrane interaction is still an unanswered question. In this work, we use state-of-the-art small angle X-ray and neutron scattering (SAXS/SANS) together with neutron reflectometry (NR) to study the membrane interaction of a series of multidomain peptides, with and without PEGylation, known to self-assemble into nanofibers. Our approach allows us to study both how the structure of the peptide and the membrane are affected by the peptide-lipid interactions. When comparing self-assembled peptides with monomeric peptides that are not able to undergo assembly due to shorter chain length, we found that the nanofibers interact more strongly with the membrane. They were found to insert into the core of the membrane as well as to absorb as intact fibres on the surface. Based on the presented results, PEGylation of the multidomain peptides leads to a slight net decrease in the membrane interaction, while the distribution of the peptide at the interface is similar to the non-PEGylated peptides. Based on the structural information, we showed that nanofibers were partially disrupted upon interaction with phospholipid membranes. This is in contrast with the considerable physical stability of the peptide in solution, which is desirable for an extended in vivo circulation time.

Halogenation as a tool to tune antimicrobial activity of peptoids

Antimicrobial peptides have attracted considerable interest as potential new class of antibiotics against multi-drug resistant bacteria. However, their therapeutic potential is limited, in part due to susceptibility towards enzymatic degradation and low bioavailability. Peptoids (oligomers of N-substituted glycines) demonstrate proteolytic stability and better bioavailability than corresponding peptides while in many cases retaining antibacterial activity. In this study, we synthesized a library of 36 peptoids containing fluorine, chlorine, bromine and iodine atoms, which vary by length and level of halogen substitution in position 4 of the phenyl rings. As we observed a clear correlation between halogenation of an inactive model peptoid and its increased antimicrobial activity, we designed chlorinated and brominated analogues of a known peptoid and its shorter counterpart. Short brominated analogues displayed up to 32-fold increase of the activity against S. aureus and 16- to 64-fold against E. coli and P. aeruginosa alongside reduced cytotoxicity. The biological effect of halogens seems to be linked to the relative hydrophobicity and self-assembly properties of the compounds. By small angle X-ray scattering (SAXS) we have demontrated how the self-assembled structures are dependent on the size of the halogen, degree of substitution and length of the peptoid, and correlated these features to their activity.

Loneliness, social isolation, and chronic disease outcomes

Background

Research suggests that loneliness and social isolation are serious public health concerns. However, our knowledge of the associations of loneliness and social isolation with specific chronic diseases is limited. The present prospective cohort study investigated (a) the longitudinal associations of loneliness and social isolation with four chronic diseases (cardiovascular disease [CVD], chronic obstructive pulmonary disease [COPD], diabetes mellitus Type 2 [T2D], and cancer), (b) the synergistic association of loneliness and social isolation with chronic disease, and (c) baseline psychological and behavioral explanatory factors.

Methods

Self-reported data from the 2013 Danish “How are you?” survey (N = 24,607) were combined with individual-level data from the National Danish Patient Registry on diagnoses in a 5 year follow-up period (2013-2018).

Results

Cox proportional hazard regression analyses showed that loneliness and social isolation were independently associated with CVD (loneliness: adjusted hazard ratio (AHR) = 1.20, 95% confidence interval [CI; 1.03, 1.40]; SI: AHR = 1.23, 95% CI [1.04, 146]) and T2D (loneliness: AHR =1.90, 95% CI [1.42, 2.55]; SI: AHR = 1.59, 95% CI [1.15, 2.21]). No significant associations were found between loneliness or social isolation and COPD and cancer, respectively. Likewise, loneliness and social isolation did not demonstrate a synergistic effect on chronic disease. Multiple mediation analysis indicated that loneliness and social isolation had an indirect effect on CVD and T2D through both baseline psychological and behavioral factors.

Conclusions

Loneliness and social isolation were independently associated with a diagnosis of CVD and T2D within a 5 year follow-up period. The associations of loneliness and social isolation with CVD and T2D were fully explained by baseline psychological and behavioral factors.

Key messages

Individuals exposed to loneliness and social isolation constitute vulnerable groups in risk of chronic disease. Psychological and behavioural factors explain the associations with chronic disease.

A qualitative study on resident engagement in a community-based health promotion intervention

Emerging evidence points towards lower quality of life, more fragile social relations and suboptimal health behaviour and health status of residents living in social housing areas characterized by ethnic diversity and socioeconomic disadvantage. Residents from social housing areas are less likely to engage in health promotion interventions compared to the rest of society. Community-based health promotion interventions developed in collaboration with the target group and adjusted to local context can affect the acceptance of and engagement in such interventions. However, few studies have investigated the potential of community-based interventions in social housing areas. This study explores resident perspectives on engagement in a community-based health promotion intervention focusing on enhancing social relations. Engagement was the key foundation for the designing and implementation of the intervention by the use of graphic facilitation. The intervention consisted of social outings to different sights and historical landmarks in Denmark. The study builds on qualitative methods including participant observations combined with pre- and post-intervention interviews with a selected group of residents (n = 9). Data were thematically analysed with a focus on participation in an everyday life context and by concepts of othering and territorial stigmatization. Engagement in the intervention was motivated by a need for establishing and enhancing social relations, and exploring the world outside the housing area. However, barriers including cultural and language differences among residents and competing contextual factors challenged engagement. We conclude that participatory community-based interventions have a potential to enhance social relations in social housing areas. Nevertheless, it is necessary to understand the motives and barriers to ensure feasible and relevant health promotion interventions and future engagement among residents living in social housing areas.

Social relations and self-rated health in a multi-ethnic social housing area undergoing demolition

Background

During the coming years, selected social housing areas in Denmark will undergo large structural changes as part of a political agenda. Previous studies on the effects of such interventions are inconclusive. Residential areas are important for the development of social relations and health. The aim of this study was to explore the associations between social relations and self-rated health (SRH) and the interaction with country of origin in an ethnically diverse social housing area undergoing demolition, and compare results with the municipality.

Methods

Data include multilingual interviewer driven surveys with residents aged 45+ years before demolition began in 2018 (N = 209) and during the demolition in 2019 (N = 132), and a health survey on municipality level (N = 1638). Information on social relations include contact frequency with and support from family, friends and neighbors. SRH was dichotomized into high/low. Descriptive and multivariate logistic regression analyses adjusted for age, sex and Western/non-Western origin are presented.

Results

In cross-sectional analyses from 2018, low contact frequency and low support increased the risk of low SRH, OR = 1.44 (0.63-3.29) and OR = 1.23 (0.62-2.48), especially when also having non-Western origin compared to having high contact frequency or support and Western origin, OR = 6.27 (1.80-21.84) and OR = 4.43 (1.68-11.69), respectively. The same association was seen in 2019 and on municipality level.

Low contact frequency in 2018 was associated with higher risk of developing or maintaining low SRH in 2019 compared to the group with high contact frequency in 2018 in longitudinal analyses, OR = 3.04 (0.91-10.91).

Conclusions

Poor social relations increased the risk of low SRH, especially when also having non-Western origin. Having poor social relations before the demolition was associated with an increased risk of developing or maintaining low SRH during the demolition in an ethnically diverse social housing area.

Key messages

Having low contact frequency before area demolition in a social housing area in Denmark increased the risk of developing or maintaining low self-rated health after demolition had begun. Having poor social relations and non-Western origin is associated with a strong increased risk of low self-rated health in a deprived ethnic diverse social housing area in Denmark.

A difference-in-difference analysis comparing a control and an intervention social housing area

Often an intervention is applied in an area (e.g. community, municipality) without it being an experiment and without a control group, this can be categorized as a natural experiment. Such a situation offers the opportunity to exploit exposure contrasts between areas regarding the specific intervention for evaluation. In the present study, we will employ the difference-in-difference approach to evaluate the natural experiment (the structural intervention) comparing measures of health and social factors retrieved from registers in the two social housing areas before and after the intervention. A 'natural experiment' study comparing individual and aggregated level differences in register-based information on health and social variables across time including the entire study period is included in the research project. The population includes all residents with an address in the study area and the control area at any point during the years 2015-2025 (∼3,000 residents in each area). All residents are linked to the Danish social and health registers by the unique personal identification number, which makes it possible to follow all permanent and former residents over time. Hereby we plan to study if the structural changes (the structural intervention, the 'natural experiment') give rise to differences in health (such as use of general practitioner, hospitalizations, use of selected medications) and social factors (e.g. divorces, income levels, unemployment) compared to the control area. The control area is representing a similar social housing area in the same municipality, which will not undergo structural changes until 2023. Findings will be evaluated drawing upon knowledge gained from the entire study from surveys and qualitative interviews as well experiences from the interventions. In this presentation, we wish to discuss how best to include the knowledge based on other methodologies in the register-based analyses.

Loneliness, social isolation and healthcare utilisation in the general population

Background

The present prospective cohort study investigated the association of loneliness and social isolation with healthcare utilisation in the general population over time. We also investigated the synergistic effect of loneliness and social isolation on healthcare utilisation.

Methods

Data from the 2013 Danish “How are you?' survey (n = 29,472) were combined with individual-level register data from the National Danish Patient Registry and the Danish National Health Service Registry in a 6-year follow-up period (2013-2018). Negative binomial regression analyses were performed while adjusting for baseline demographics, chronic disease, and healthcare utilisation during the follow-up period.

Results

Loneliness was significantly associated with number of GP visits (incident-rate ratio (IRR) = 1.06, 95% confidence interval (CI) [1.01, 1.13]), emergency admissions (IRR = 1.19, 95% CI [1.03, 1.37]) and number of hospital admission days (IRR = 1.32, 95% CI [1.08, 1.62]). No significant associations were found between social isolation and healthcare utilisation with one minor exception, in which social isolation was associated with less planned admissions (IRR = .88, 95% CI [.78, .99]). Finally, loneliness and social isolation demonstrated a synergistic effect on number of visits to the GP (IRR = .87, 95% CI [.78, .98]) and number of hospital admission days (IRR = .67, 95% CI [.45, .98]).

Conclusions

Our findings suggest that loneliness is a risk factor for primary and secondary healthcare utilisation, independently of social isolation, baseline demographics, chronic disease, and healthcare utilisation during the follow-up period.

Key messages

Loneliness is an independent risk factor for healthcare utilisation in the general population. Social isolation is not associated with healthcare utilisation in the general population.

What possibilities and barriers for community engagement does graphical facilitation establish?

Participatory approaches are appropriate to apply in interventions aiming at improving health and wellbeing in the everyday life of people living in deprived areas. However, more research is needed on how participation is staged, what negotiations of power are possible and to what extent the applied methods for engagement are accessible to a less affluent spectrum of residents. We apply an interdisciplinary approach to allow theoretical reflections on the applied strategy of participation. The intervention employs the use of physical materials through the performance of drawing to make participation less dependent of language and writing skills and hereby more equal. With this participatory intervention study, we aim to empower residents to increase their ability to act on their own health, i.e. social relations and life quality. We apply graphical facilitation by using physical drawing materials to explore how this method can give voice to the residents by providing them the opportunity to tell their story - from where they came to where they hope to go. The main component in the study is four participatory workshops in spring 2020: a) two focusing on teaching of basic drawing skills; b) one where the residents individually draw their own life story; c) one where the residents draw their shared vision of their community. This intervention study aims to contribute to health promotion by exploring generic methods to engage residents in deprived areas. The intended outcome is to empower residents by giving them a means of communication transferable to other settings in everyday life.

Experiences and challenges in collecting survey data in an ethnically diverse social housing area

Socio-economically disadvantaged groups are characterised by a higher burden of disease than the background population. Paradoxically, they are often underrepresented in health research. Failing to include socio-economically disadvantaged groups in research impairs the ability to address the social mechanisms creating health disparities. The study describes how we have tried to accommodate identified challenges from the literature in conducting a questionnaire survey in a socio-economically deprived and ethnically diverse social housing area, and which new challenges we identified. The survey is planned before, during and after the structural changes take place. Through innovative approaches, we sought to accommodate identified barriers to reaching participants. The questionnaire was translated from Danish to the seven most prevalent languages in the area, based on data from the national register. A survey corps of native speaking interviewers went door-to-door to perform face-to-face interviews. To encourage participation, we used a recruitment strategy inspired by ethnographic data collection traditions, such as local presence, participation in local activities, and graphic facilitation on invitation letters. Wave 1 and 2 had a response rate of 35% (N = 209) and 22% (N = 132), respectively. 79 respondents participated in both waves. Despite our efforts to accommodate identified challenges such as language, illiteracy, and mistrust, the response rates are low. We identified new challenges in recruiting participants including participation fatigue, frustration with the restructure process, and a feeling of limited individual gain from participation. Many challenges are associated with conducting research among socio-economically disadvantaged groups. Documenting processes and learning from experiences are important steps in including groups with lower socio-economic status in health research in order to address the underlying social mechanisms creating health disparities.

Tale of Two Tails: Molecular Exchange Kinetics of Telechelic Polymer Micelles

Telechelic polymers contain two chain ends that are able to promote self-assembly into "flowerlike" or interconnected micellar structures. Here, we investigate the molecular exchange kinetics of such micelles using time-resolved small-angle neutron scattering. We show that the activation energies of monofunctional and telechelic chain exchange are identical. This demonstrates that the two chain ends are not simultaneously released in a single event. Instead, the results show that, contrary to regular micelles, the kinetics occurs in a multistep process involving a collision-induced single-molecule exchange mechanism where the exchange rate is directly proportional to the polymer concentration. We show that this novel mechanism can be quantitatively explained by a simple kinetic model.

Structure-Activity Study of an All-d Antimicrobial Octapeptide D2D

The increasing emergence of multi-drug resistant bacteria is a serious threat to public health worldwide. Antimicrobial peptides have attracted attention as potential antibiotics since they are present in all multicellular organisms and act as a first line of defence against invading pathogens. We have previously identified a small all-d antimicrobial octapeptide amide kk(1-nal)fk(1-nal)k(nle)-NH2 (D2D) with promising antimicrobial activity. In this work, we have performed a structure-activity relationship study of D2D based on 36 analogues aimed at discovering which elements are important for antimicrobial activity and toxicity. These modifications include an alanine scan, probing variation of hydrophobicity at lys5 and lys7, manipulation of amphipathicity, N-and C-termini deletions and lys-arg substitutions. We found that the hydrophobic residues in position 3 (1-nal), 4 (phe), 6 (1-nal) and 8 (nle) are important for antimicrobial activity and to a lesser extent cationic lysine residues in position 1, 2, 5 and 7. Our best analogue 5, showed MICs of 4 µg/mL against A. baumannii, E. coli, P. aeruginosa and S. aureus with a hemolytic activity of 47% against red blood cells. Furthermore, compound 5 kills bacteria in a concentration-dependent manner as shown by time-kill kinetics. Circular dichroism (CD) spectra of D2D and compounds 1-8 showed that they likely fold into α-helical secondary structure. Small angle x-ray scattering (SAXS) experiments showed that a random unstructured polymer-like chains model could explain D2D and compounds 1, 3, 4, 6 and 8. Solution structure of compound 5 can be described with a nanotube structure model, compound 7 can be described with a filament-like structure model, while compound 2 can be described with both models. Lipid interaction probed by small angle X-ray scattering (SAXS) showed that a higher amount of compound 5 (~50-60%) inserts into the bilayer compared to D2D (~30-50%). D2D still remains the lead compound, however compound 5 is an interesting antimicrobial peptide for further investigations due to its nanotube structure and minor improvement to antimicrobial activity compared to D2D.

A life course analysis of income and incident AMI - a Danish register based cohort study

Background

Social inequality in ischemic heart disease has been related to socioeconomic position in childhood, early and late adulthood. However, the impact of relative level of accumulated income periods across adult life course and the potential gender and age differences has not been investigated.

The aim was to investigate the association between relative level of accumulated income across the life course and Acute myocardial infarction (AMI) from age 60+ and to study if the associations differ by gender and exposure in different age groups (30-39 years, 40-49 years and 50-59 years).

Methods

All Danes born 1935-54 N = 1,235,139 were followed-up in registers for incident AMI (ICD8: 410, ICD10: I20, I21) from age 60+, (42,669 cases). The The Accumulated Proportional Deviation from Median Equivalized Income = APDMEI for each gender/age /calendar year strata was constructed and divided in quartiles. The analyses stratified by birth cohort included all Danes born in 1955-70 (alive and reached age 40) N = 1,144,264, 1945-64 (alive and reached age 50), N = 1,434,769, 1935-1954 (alive and reached age 60) N = 1,235,139 including outcomes in the following 10 year period. Cox’s proportional hazard models adjusted for educational level, ethnic background and birth cohort.

Results

Among men, those in the lowest APDMEI quartile had a HR 1.40 (1.35-1.45) of AMI compared to the highest quartile, second and third highest quartiles had HR of 1.24 (1.20-1.28) and 1.14 (1.10-1.18), respectively. Among women the lowest quartile had a HR of 1.78 (1.69-1.88), the second 1.45 (1.37-1.53) and the third 1.19 (1.13-1.26). The social gradient was similar across the different age-groups.

Conclusions

The risk of AMI increased with lower levels of relative accumulated income across the life course. While men generally had a higher risk of AMI, the social gradient was steeper in women. There was no indication of a specific sensitive age period for exposure to relative level of accumulated income.

Key messages

Accumulated low income is associated with higher AMI risk in both men and women, but with larger relative differences between high and low accumulated income in women. This study adds a new approach to the study of inequalities in AMI by integrating duration and extent of low income into a relative measure of accumulated income.

Economic hardship over twenty-two consecutive years of adult life and markers of early ageing

Background

The authors examined the associations between annual measures of economic hardship (EH) across 22 years of adulthood and objective measures of early ageing in a Danish late-middle aged population.

Methods

A linkage of longitudinal register data from Statistics Denmark covering the period 1987-2008 and cross-sectional survey data from the Copenhagen Ageing and Midlife Biobank collected in 2009-11 (N = 5,575). EH was defined as < 60% of the National median equivalized household disposable income and two exposures were calculated: 1) a categorical measure of total number if years in EH, and 2) trajectories of the probability of EH being low, declining, rising or high. Early ageing outcomes included four measures of physical capability, three inflammatory markers and one cognitive test. Associations were analyzed using linear regression models adjusted for sex, age, cohort, education, baseline income and long-term parental unemployment/financial problems.

Results

Four or more years in EH (reference=null years in EH) was related to poorer physical capability (chair rise: -1.49 counts/30 seconds [95% confidence interval (CI) -2.36, -0.61], hand grip strength: -1.22 kg [95% CI -2.38, -0.07], jump height: -1.67 cm [95% CI -2.44, -0.91] and balance: 18% [95% CI 9, 28]), poorer cognitive function (Intelligenz-Struktur-Test: -1.50 points [95% CI -2.89, -0.12]) and higher inflammatory levels (C-reactive protein: 22% [95% CI 4, 44], and Interleukin-6: 23% [95% CI 10, 39]). Comparing the four EH trajectories, people with a high vs. low probability of EH over time had poorer physical capability (chair rise: -1.70 counts/30 seconds [95% CI -3.38, -0.01], grip: -4.33 kg [95% CI -6.50, -2.16], jump: -1.68 cm [95% CI -3.12, -0.25], and balance: 31% [95% CI 12, 52]). No associations were observed with Tumor necrosis factor α.

Conclusions

This study suggests that sustained EH across adulthood may lead to early ageing.

Key messages

Sustained economic hardship in adulthood may lead to early ageing. Being in economic hardship for a few years is not associated with early ageing.

Structure and thermodynamics of mixed polymeric micelles with crystalline cores: tuning properties via co-assembly

We investigate micelles formed by mixtures of n-alkyl-poly(ethylene oxide) block copolymers, Cn-PEO, with different alkyl block lengths in aqueous solution. This model system has previously been used to shed light on the interplay between exchange kinetics and crystallinity in self-assembling systems [König et al., Phys. Rev. Lett., 2019, 122, 078001]. Now we report on the structure and thermodynamics of these micelles by combining results from small-angle X-ray scattering, differential scanning calorimetry and volumetric measurements. We show that mixed micelles are formed despite the fact that length-mismatched n-alkanes of similar weights in bulk tend to demix below the crystallization temperature. Instead, the system exhibits similar properties as single-component micelles but with a modulated melting region. Interestingly, the melting point depression due to self-confinement within the micellar core can be approximately described by a generalized Gibbs-Thomson equation, similar to single-component micelles [Zinn et al. Phys. Rev. Lett., 2014, 113, 238305]. Furthermore, we find a novel scaling law for these micelles where, at least for larger n, the aggregation number scales with the third power of the length of the hydrophobic block, Nagg ∝ n3. Possibly, there might be a cross-over from the conventional Nagg ∝ n2 behaviour around n ≈ 19. However, the reason for such a transition as well as the strong n dependence remains a challenge and requires more theoretical work.

Time-resolved small-angle neutron scattering as a probe for the dynamics of lipid exchange between human lipoproteins and naturally derived membranes

Atherosclerosis is the main killer in the western world. Today’s clinical markers include the total level of cholesterol and high-/low-density lipoproteins, which often fails to accurately predict the disease. The relationship between the lipid exchange capacity and lipoprotein structure should explain the extent by which they release or accept lipid cargo and should relate to the risk for developing atherosclerosis. Here, small-angle neutron scattering and tailored deuteration have been used to follow the molecular lipid exchange between human lipoprotein particles and cellular membrane mimics made of natural, “neutron invisible” phosphatidylcholines. We show that lipid exchange occurs via two different processes that include lipid transfer via collision and upon direct particle tethering to the membrane, and that high-density lipoprotein excels at exchanging the human-like unsaturated phosphatidylcholine. By mapping the specific lipid content and level of glycation/oxidation, the mode of action of specific lipoproteins can now be deciphered. This information can prove important for the development of improved diagnostic tools and in the treatment of atherosclerosis.

Lewis and AB0 blood group-phenotypes in periodontitis, cardiovascular disease, obesity and stroke

The AB0 blood group has been linked to ischaemic heart disease, stroke, and periodontal disease, while the Lewis blood group has been linked to ischaemic heart disease and obesity, all of which have been associated with periodontitis. AB0 or Lewis blood group phenotype may therefore constitute common hereditary components predisposing to these disorders. In this study, we investigated if blood group phenotype associated with periodontitis in a subpopulation consisting of 702 participants from a Danish cross-sectional cohort and, secondarily, attempted to confirm their association with hypertension, ischaemic heart disease, stroke, and obesity. No significant association between blood group phenotype and periodontitis was detected, nor were previously reported associations between blood group phenotype and hypertension, ischaemic heart disease, stroke, and obesity confirmed. This may, at least partly, be attributed to differences in study type, outcome definitions, cohort sizes, and population attributable factors. However, our results suggested a strong association between self-reported stroke and the Lewis (a−b−) phenotype (P = 0.0002, OR: 22.28; CI 95: 4.72–131.63).

Cooperativity during Melting and Molecular Exchange in Micelles with Crystalline Cores

Molecular exchange processes are important equilibration and transport mechanisms in both synthetic and biological self-assembled systems such as micelles, vesicles, and membranes. Still, these processes are not entirely understood, in particular the effect of crystallinity and the interplay between cooperative melting processes and chain exchange. Here we focus on a set of simple polymer micelles formed by binary mixtures of poly(ethylene oxide)-mono-n-alkyl-ethers (C_{n}-PEO5) which allows the melting point to be tuned over a wide range. We show that the melting transition is cooperative in the confined 4-5 nm micellar core, whereas the exchange process is widely decoupled and unimeric in nature. As confirmed by differential scanning calorimetry, the total activation energy for ejecting a molecule out of the micellar core below the melting point is the sum of the enthalpy of fusion and the corresponding activation energy in the melt state. This suggests that a "local, single-chain melting process" preludes the molecular diffusion out of the micelle during chain exchange.

Striking Effect of Polymer End-Group on C60 Nanoparticle Formation by High Shear Vibrational Milling with Alkyne-Functionalized Poly(2-oxazoline)s

Buckminsterfullerene (C₆₀) has a large potential for biomedical applications. However, the main challenge for the realization of its biomedical application potential is to overcome its extremely low water solubility. One approach is the coformulation with biocompatible water-soluble polymers, such as poly(2-oxazoline)s (PAOx), to form water-soluble C₆₀ nanoparticles (NPs). However, uniform and defined NPs have only been obtained via a thin film hydration method or using cyclodextrin-functionalized PAOx. Here, we report the mechanochemical preparation of defined and stable C₆₀:PAOx NPs by the introduction of a simple alkyne group as a polymer end-group. The presence of this alkyne bond is proven to be crucial in the mechanochemical synthesis of stable, defined sub-100 nm C₆₀:PAOx NPs, with high C₆₀ content up to 8.9 wt %.

Grip Work Measurement with the Jamar Dynamometer: Validation of a Simple Equation for Clinical Use

OBJECTIVES

Previously, we developed and validated an easy test to measure muscle fatigability during sustained maximal handgrip contraction in older persons using a Martin Vigorimeter device. This study aimed at validating the equation to estimate grip work (GW) during sustained maximal handgrip contraction, by monitoring continuously the grip strength (GS) decay using a Jamar Dynamometer-like (JD) device.

DESIGN

Cross sectional, explorative study.

SETTING

Data collection took place at The National Research Centre for the Working Environment in Copenhagen, Denmark.

PARTICIPANTS

962 subjects, belonging to a subgroup of the Copenhagen Aging and Midlife Biobank, were enrolled.

METHODS

GS was recorded continuously during sustained maximal contraction until it dropped to 50% of its maximum and fatigue resistance (FR, time to fatigue) was noted. GW, area under the force-time curve, was compared to its estimate which was calculated as GWestimated=GSmax*0.75*FR.

RESULTS

Excellent correlation was found between GWestimated and GWmeasured (R²=0.98 p<0.001). The equation slightly overestimated GW by 6.04 kg*s (95% CI[-0.08, 12.15]) with a coefficient of variation method error of 6%.

CONCLUSION

GW estimation is a valid parameter reflecting muscle work output during a sustained maximal grip effort in healthy middle-aged community-dwelling persons when using a JD. GW estimation is a promising outcome parameter in comprehensive geriatric assessment and its validation for commonly used instruments in geriatric practice will increase its clinical implementation.

Resolving the structural interactions between antimicrobial peptides and lipid membranes using small-angle scattering methods: the case of indolicidin

Using small angle X-ray and neutron scattering (SAXS/SANS) and detailed theoretical modelling we have elucidated the structure of the antimicrobial peptide, indolicidin, and the interaction with model lipid membranes of different anionic lipid compositions mimicking typical charge densities found in the cytoplasmic membrane of bacteria. First, we show that indolicidin displays a predominantly disordered, random chain conformation in solution with a small fraction (≈1%) of fiber-like nanostructures that are not dissolved at higher temperatures. The peptide is shown to strongly interact with the membranes at all charge densities without significantly perturbing the lipid bilayer structure. Instead, the results show that indolicidin inserts into the outer leaflet of the lipid vesicles causing a reduced local order of the lipid packing. This result is supported by an observed change in the melting point of the lipids upon addition of the peptide, as seen by differential scanning calorimetry experiments. The peptide does not to our observation affect the thickness of the membrane or form distinct structural pores in the membrane at physiologically relevant concentrations as has been previously suggested as an important mode of action. Finally, using sophisticated contrast variation SANS, we show that the peptide does not affect the random lateral distribution of anionic lipids in the membrane. Together, these results demonstrate that the structural aspects of the mode of action of antimicrobial peptides can be elucidated in detail using SAS techniques with liposomes as model systems.

Injectable synthetic hydrogel for bone regeneration: Physicochemical characterisation of a high and a low pH gelling system

Hybrid poly(ethylene glycol)-co-peptide hydrogels are a versatile platform for bone regeneration. For the use as injectable scaffolds, a good understanding of reaction kinetics and physical properties is vital. However, these factors have not yet been comprehensively illuminated. We show that gelation time can be effectively controlled by pH without affecting the elasticity of the formed hydrogels. Maleimide functionalised PEG gels at lower pH and produces more densely cross-linked networks than vinylsulfone functionalised PEG. Both form non-ideal networks. The elastic moduli on the order of a few kPa are in good agreement with the structural characterisation. Primary human osteoblasts cultured in proximity to bulk gels were not adversely affected in vitro. The results demonstrate that hybrid PEG-peptide hydrogels can be tailored to the requirements of in situ gelation. Attributed to their increased structural properties and a higher tolerance towards low pH, maleimide functionalised hydrogels might provide a better alternative for injectable applications.