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Multidrug resistance (MDR) is a rising threat to global health because the number of essential antibiotics used for treating MDR infections is increasingly compromised. In this work we report a group of new amphiphilic peptides (AMPs) derived from the well-studied G 3 (G(IIKK) 3 I-NH 2 ) to fight infections from Gram-positive bacteria including susceptible Staphylococcus aureus and methicillin-resistant Staphylococcus aureus (MRSA), focusing on membrane interactions. Time-dependent killing experiments revealed that substitutions of II by WW (GWK), II by FF (GFK) and KK by RR (GIR) resulted in improved bactericidal efficiencies compared to G 3 (GIK) on both S. aureus and MRSA, with the order of GWK > GIR > GFK > GIK. Electronic microscopy imaging revealed structural disruptions of AMP binding to bacterial cell walls. Fluorescence assays including AMP binding to anionic lipoteichoic acids (LTA) in cell-free and cell systems indicated concentration and time-dependent membrane destabilization associated with bacterial killing. Furthermore, AMP's binding to anionic plasma membrane via similar fluorescence assays revealed a different extent of membrane depolarization and leakage. These observations were supported by the penetration of AMPs into the LTA barrier and the subsequent structural compromise to the cytoplasmic membrane as revealed from SANS (small angle neutron scattering). Both experiments and molecular dynamics (MD) simulations revealed that GWK and GIR could make the membrane more rigid but less effective in diffusive efficiency than GIK and GFK through forming intramembrane peptide nanoaggregates associated with hydrophobic mismatch and formation of fluidic and rigid patches. The reported peptide-aggregate-induced phase-separation emerged as a crucial factor in accelerated membrane disintegration and fast bacterial killing. This work has demonstrated the importance of membrane interactions to the development of more effective AMPs and the relevance of the approaches as reported in assisting this area of research., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Inc.)

Nonionic surfactant aerosols play a crucial role in many industries, but they can cause acute irritation to users' eyes during spraying. This cytotoxic process is associated with corneal cell necrosis causing cell membrane disruption. Industrial grade surfactants are typically polydisperse mixtures described by their nominal chemical structure but how the polydispersity affects their interactions with cell membrane, remains largely unexplored. A better understanding could benefit product formulations to maximise their efficiency whilst minimising their toxicity to the users. In this study, poly-oxyethylene glycol monododecyl ethers (C 12 E 4 , C 12 E 23 ) were used to form ideal binary surfactant mixtures. The cytotoxicities of mono and polydispersed surfactants towards human corneal epithelial cells were examined, followed by a series of biophysical characterisations of interactions between surfactants and model cell membranes. Notably, to probe the journey of individual C 12 E 4 and C 12 E 23 surfactant molecules across the cell membrane from a binary surfactant mixture, "two-colour" neutron reflection measurements were achieved via Hydrogen/Deuterium substitution. The relative distributions of C 12 E 4 and C 12 E 23 across cell membranes and their nanostructural conformations revealed a synergistic membrane-lytic ability initiated by surfactant mixing, with the more hydrophobic C 12 E 4 exhibiting stronger membrane binding potency than the hydrophilic C 12 E 23 . The exact molar ratio of C 12 E 4 against C 12 E 23 in the mixture determined how the mixed surfactant interacted with the cell membrane, and how the process directly impacted cytotoxicity and eye irritation. Thus, the cytotoxicity of polydisperse surfactants is not the same as monodisperse surfactant of the same average structure. This work provides a useful basis for the assessment of surfactant mixing by balancing their efficiency and toxicity., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: The current work is part of collaborative research carried out at Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences and the University of Manchester, with input from ISIS neutron spallation source and China Spallation Neutron Source. The funding support has been formally acknowledged. The authors have no conflict of interest., (Copyright © 2024 Elsevier Inc. All rights reserved.)

The co-assembly of different peptide chains usually leads to the formation of intricate architectures and sophisticated functions in biological systems. Although the co-assembly of stereoisomeric peptides represents a facile and flexible strategy for the synthesis of peptide-based nanomaterials with novel structures and potentially interesting properties, there is a lack of a general knowledge on how different isomers pack during assembly. Through the combined use of simulations and experimental observations, we report that heterochiral pairing is preferred to homochiral pairing at the molecular scale but self-sorting dictates beyond the molecular level for the mixtures of the short stereoisomeric β-sheet peptides I 3 K (Ile-Ile-Ile-Lys). Furthermore, we demonstrate that flat β-sheets and fibril morphology are always preferred to twisted ones during heterochiral pairing and subsequent assembly. However, the heterochiral pairing into flat morphology is not always at an equimolar ratio. Instead, a non-equimolar ratio (1:2) is observed for the mixing of homochiral L I 3 L K and heterochiral L I 3 D K, whose strand twisting degrees differ greatly. Such a study provides a paradigm for understanding the co-assembly of stereoisomeric peptides at the molecular scale and harnessing their blending for targeted nanostructures., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Background: Clinical treatments ofgastric infections using antibiotics suffer from the undesired killing of commensal bacteria and emergence of antibiotic resistance. It is desirable to develop pH-responsive antimicrobial peptides (AMPs) that kill pathogenic bacteria such as H. pyloriand resistant E. coli under acidic environment with minimal impact to commensal bacteria whilst not causing antibiotic resistance., Experiments: Using a combined approach of cell assays, molecular dynamics (MD) simulations and membrane models facilitating biophysical and biochemical measurements including small angle neutron scattering (SANS), we have characterized the pH-responsive physiochemical properties and antimicrobial performance of two amphiphilic AMPs, GIIKDIIKDIIKDI-NH 2 and GIIKKIIDDIIKKI-NH 2 (denoted as 3D and 2D, respectively), that were designed by selective substitutions of cationic residues of Lys (K) in the extensively studied AMP G(IIKK) 3 I-NH 2 with anionic residue Asp (D)., Findings: Whilst 2D kept non-ordered coils across the entire pH range studied, 3D displayed a range of secondary structures when pH was shifted from basic to acidic, with distinct self-assembly into nanofibers in aqueous environment. Further experimental and modeling studies revealed that the AMPs interacted differently with the inner and outer membranes of Gram-negative bacteria in a pH-responsive manner and that the structural features characterized by membrane leakage and intramembrane nanoaggregates revealed from fluorescence spectroscopy and SANS were well linked to antimicrobial actions. Different antimicrobial efficacies of 2D and 3D were underlined by the interplay between their ability to bind to the outer membrane lipid LPS (lipopolysaccharide), outer membrane permeability change and inner membrane depolarization and leakage. Furthermore, AMP's binding with the inner membrane under acidic condition caused both the dissipation of membrane potential (Δψ) and the continuous dissipation of transmembrane ΔpH, with Δψ and ΔpH being the key components of the proton motive force. Combinations of antibiotic (Minocycline) with the pH-responsive AMP generated the synergistic effects against Gram-negative bacteria only under acidic condition. These features are crucial to target applications to gastric infections, anti-acne and wound healing., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Crown Copyright © 2023. Published by Elsevier Inc. All rights reserved.)

Hypothesis: It is widely regarded that antimicrobial peptides (AMPs) kill bacteria by physically disrupting microbial membranes and causing cytoplasmic leakage, but it remains unclear how AMPs disrupt the outer membrane (OM) of Gram-negative bacteria (GNB) and then compromise the inner membrane. We hypothesise that different AMPs impose different structural disruptions, with direct implications to their antimicrobial efficacies., Experiments: The antimicrobial activities of three typical AMPs, including the designed short AMP, G 3 , and two natural AMPs, melittin and LL37, against E. coli and their haemolytic activities were studied. Lipopolysaccharide (LPS) and anionic di-palmitoyl phosphatidyl glycerol (DPPG) monolayer models were constructed to mimic the outer membrane and inner membrane leaflets of Gram-negative bacteria. The binding and penetration of AMPs to the model lipid monolayers were systematically studied by neutron reflection via multiple H/D contrast variations., Finding: G 3 has relatively high antimicrobial activity, low cytotoxicity, and high proteolytic stability, whilst melittin has significant haemolysis and LL37 has weaker antimicrobial activity. G 3 could rapidly lyse LPS and DPPG monolayers within 10-20 min. In contrast, melittin was highly active against the LPS membrane, but the dynamic process lasted up to 80 min, with excessive stacking in the OM. LL37 caused rather weak destruction to LPS and DPPG monolayers, leading to massive adsorption on the membrane surface without penetrating the lipid tail region. These findings demonstrate that the rationally designed AMP G 3 was well optimised to impose most effective destruction to bacterial membranes, consistent with its highest bactericidal activity. These different interfacial structural features associated with AMP binding shed light on the future development of active and biocompatible AMPs for infection and wound treatments., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

Hypothesis: Self-assembly of peptides is influenced by both molecular structure and external conditions, which dictate the delicate balance of different non-covalent interactions that driving the self-assembling process. The shifting of terminal charge residue is expected to influence the non-covalent interactions and their interplay, thereby affecting the morphologies of self-assemblies. Therefore, the morphology transition can be realized by shifting the position of the terminal charge residue., Experiments: The structure transition from thin nanofibers to giant nanotubes is realized by simply shifting the C-terminal lysine of ultrashort Ac-I 3 K-NH 2 to its N-terminus. The morphologies and detailed structure information of the self-assemblies formed by these two peptides are investigated systemically by a combination of different experimental techniques. The effect of terminal residue on the morphologies of the self-assemblies is well presented and the underlying mechanism is revealed., Findings: Giant nanotubes with a bilayer shell structure can be self-assembled by the ultrashort peptide Ac-KI 3 -NH 2 with the lysine residue close to the N-terminal. The Ac-KI 3 -NH 2 dimerization through intermolecular C-terminal H-bonding promotes the formation of a bola-form geometry, which is responsible for the wide nanotube assembly formation. The evolution process of Ac-KI 3 -NH 2 nanotubes follows the "growing width" model. Such a morphological transformation with the terminal lysine shift is applicable to other analogues and thus provides a facile approach for the self-assembly of wide peptide nanotubes, which can expand the library of good template structures for the prediction of peptide nanostructures., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Hypothesis: Nonionic surfactants are widely used as co-formulants in agrochemical sprays. During spraying, they may come into direct contact with humans and animals, causing irritation in different tissues. However, how the molecular structures of these surfactants affect their toxicity towards human eye and skin at the cellular level has not been well characterised., Experiment: In this study, the cytotoxicities of two sets of nonionic surfactants (alkyl ethoxylate, C n E m ) against human corneal and skin cell lines were examined, with one set composed of varied surfactant head length but fixed tail length (C 12 E 4-23 ) and the other set oppositely composed (C 10-16 E 6 ). The cell viability and morphology against different nonionic surfactants for varied exposure times were studied, followed by characterisation of their membrane-lytic ability., Finding: Nonionic surfactants with intermediate amphiphilicity killed cells rapidly due to their strong membrane-lytic power. Those with weak or strong hydrophobicity exhibited low cytotoxicity but had different modes of action depending on their hydrophobicity. Hydrophobic surfactants were found to adsorb on to cell membranes with no observed structural damage for 2 hr. Hydrophilic surfactants were also found to adsorb on to cell membranes but did cause mild structural changes. While the changes were not sufficient to elicit large cytoplasmic leakage over short periods of time, membrane associations did cause cell shrinkage which eventually resulted in cell death over longer exposure periods. These results revealed that the specific amphiphilic nature of nonionic surfactants played a crucial role in determining their cytotoxicity. This work provided a useful basis for the assessment of amphiphilicity of the nonionic surfactants used in agrochemical sprays by balancing their efficiency, toxicity and environmental impact., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

Hypothesis: Acyl-l-carnitines (C n LCs) are potentially important as biosurfactants in drug delivery and tissue engineering due to their good biocompatibility. However, little is currently known about the basic interfacial behavior underlying their technological applications. Following our previous characterization of their solution aggregation and adsorption at the air/water interface, this work examines how they adsorb at the hydrophilic solid/liquid interface., Experiments: As the SiO 2 /water interface has served as the model substrate for many interfacial adsorption studies, so it has been used in this work as the solid substrate to facilitate dynamic adsorption by spectroscopic ellipsometry (SE) and structural determination of the adsorbed layers by neutron reflection (NR) under different conditions at the SiO 2 /water interface from a group of C n LC (n = 12, 14, and 16)., Findings: C n LC surfactants are zwitterionic at neutral pH. They reached saturated adsorption above their critical micellar concentrations (CMCs) and formed a sandwich bilayer with a head-tail-head structure at the hydrophilic SiO 2 /water interface. The total thicknesses of the adsorbed layers at CMC were found to be 33 ± 2, 35 ± 2, and 37 ± 2 Å for C 12 LC, C 14 LC, and C 16 LC, respectively, with their inner and outer head layers remaining similar but the thickness of the interdigitated middle layer increasing with acyl chain length. As the solution becomes acidic, the carboxyl groups become protonated and the l-carnitine heads are net positively charged, resulting in increased repulsion between the head groups. In this situation, the C n LC surfactants are adsorbed as distinct aggregates to reduce repulsive interaction, resulting in reduced surfactant volume fraction and layer thickness. However, a high ionic strength can screen the repulsive interaction and enhance the adsorbed amount, effectively diminishing the impact of pH. This information provides a useful basis for exploring the technological applications of C n LCs involving a solid substrate., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

Hypothesis: Nonionic alkyl ethoxylate surfactants are widely used in agrochemicals to facilitate the permeation of systemic herbicides and fungicides across the plant waxy film. Industrial grade surfactants are often highly mixed and how the mixing affects their interactions with pesticides and wax films remains largely unexplored. A better understanding could enable design of mixed nonionic surfactants for herbicides and fungicides to maximize their efficiency and reduce wastage whilst controlling their impact on plant wax films., Experiment: In this study, nonionic surfactants with general structure n-oxyethylene glycol monododecyl ether (C 12 E n ) were used to form surfactant mixtures with the same average ethoxylate numbers but different hydrophilic-lipophilic balance (HLB) values. Their mixed micellar systems were then used to solubilize a herbicide diuron (DN) and a fungicide cyprodinil (CP), followed by plant wax solubilization upon contact with wax films. These processes were monitored by 1 H NMR and SANS., Finding: Pesticide solubilization made surfactant micelles effectively more hydrophobic but subsequent wax dissolution caused pesticide release and the restoration of the micellar amphiphilicity. Nonionic surfactants with lower HLBs form larger nanoaggregates, show enhanced wettability, and have better ability to solubilize and permeate pesticides across the wax film, but may cause significant damage to plant growth. These observations help explain why herbicides applied on weeds would benefit from surfactants with lower HLB values while fungicides require surfactants with HLBs to balance between delivery efficiency and potential phytotoxicity risks., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022. Published by Elsevier Inc.)

Hypothesis: l-carnitines in our body systems can be readily converted into acyl-l-carnitines which have a prominent place in cellular energy generation by supporting the transport of long-chain fatty acids into mitochondria. As biocompatible surfactants, acyl-l-carnitines have potential to be useful in technical, personal care and healthcare applications. However, the lack of understanding of the effects of their molecular structures on their physical properties has constrained their potential use., Experiments: This work reports the study of the influence of the acyl chain lengths of acyl-l-carnitines (C n LC) on solubility, surface adsorption and aggregation. Critical micellar concentrations (CMCs) of C n LC were determined by surface tension measurements. Neutron reflection (NR) was used to further examine the structure and composition of the adsorbed C n LC layer. The structural changes of the micellar aggregates under different concentrations of C n LC, pH and ionic strength were determined by dynamic light scattering (DLS) and small angle neutron scattering (SANS)., Findings: C 12 LC is fully soluble over a wide temperature and concentration range. There is however a strong decline of solubility with increasing acyl chain length. The adsorption and aggregation behavior of C 14 LC was therefore studied at 30 °C and C 16 LC at 45 °C. The solubility boundaries displayed distinct hysteresis with respect to heating and cooling. The CMCs of C 12 LC, C 14 LC and C 16 LC at pH 7 were 1.1 ± 0.1, 0.10 ± 0.02 and 0.010 ± 0.005 mM, respectively, with the limiting values of the area per molecule at the CMC being 45.4 ± 2, 47.5 ± 2 and 48.8 ± 2 Å 2 and the thicknesses of the adsorbed C n LC layers at the air/water interface increasing from 21.5 ± 2 to 22.6 ± 2 to 24.2 ± 2 Å, respectively. All three surfactants formed core-shell spherical micelles with comparable dimensional parameters apart from an increase in core radius with acyl chain length. This study outlines the effects of acyl chain length on the physicochemical properties of C n LCs under different environmental conditions, serving as a useful basis for developing their potential applications., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: [The current work is part of fundamental collaborative research carried out at the University of Manchester, with input from Lonza and ISIS Neutron Facility at STFC. The funding support has been formally acknowledged. The authors have no conflict of interest]., (Copyright © 2021. Published by Elsevier Inc.)

Hypothesis: l-carnitine plays a crucial role in the cellular production of energy by transporting fatty acids into mitochondria. Acylated l-carnitines are amphiphilic and if appropriate physical properties were demonstrated, they could replace many currently used surfactants with improved biocompatibility and health benefits., Experiments: This work evaluated the surface adsorption of lauroyl-l-carnitine (C 12 LC) and its aggregation behavior. The size and shape of the aggregates of C 12 LC surfactant were studied at different temperatures, concentrations, pH and ionic strength by dynamic light scattering (DLS) and small-angle neutron scattering (SANS). Surface tension measurements were carried out to determine the critical micellar concentration (CMC) of C 12 LC. Combining with the Gibbs equation, the surface excess at different concentrations could be determined. Neutron reflection (NR) was used to determine the structure of the adsorbed layer at the air/water interface with the help of isotopic contrast variations., Findings: At pH 7, the limiting area per molecule (A CMC ) of the zwitterionic C 12 LC adsorbed layer at the air/water interface was found to be 46 Å 2 from surface tension and neutron reflection, smaller than the values of C 12 PC, C 12 E 5 , DTAB, C 12 C 4 betaine and C 12 C 8 betaine but close to that of SDS. A pronounced surface tension minimum at pH 2 at the low ionic strength was linked to a minimum value of area per molecule of about 30 Å 2 , indicating the competitive adsorption from traces of lauric acid produced by hydrolysis of C 12 LC. As the concentration increased, area per molecule reached a plateau of 37-39 Å 2 , indicating the dissolution of the more surface-active lauric acid into the micelles of C 12 LC. DLS and SANS showed that the size and shape of micelles had little response to temperature, concentration, ionic strength or pH. The SANS profiles measured under 3 isotopic contrasts could be well fitted by the core-shell model, giving a spherical core radius of 15.7 Å and a shell thickness of 10.5 Å. The decrease of pH led to more protonated carboxyl groups and more positively charged micelles, but the micellar structures remained unchanged, in spite of their stronger interaction. These features make C 12 LC potentially attractive as a solubilizing agent., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021. Published by Elsevier Inc.)

Hypothesis: Surfactants have been widely used as adjuvants in agri-sprays to enhance the solubility of pesticides in foliar spray deposits and their mobility through leaf cuticles. Previously, we have characterised pesticide solubilisation in nonionic surfactant micelles, but what happens when pesticides become solubilised in anionic, cationic and zwitterionic and their mixtures with nonionic surfactants remain poorly characterised., Experiments: To facilitate characterisations by SANS and NMR, we used nonionic surfactant hexaethylene glycol monododecyl ether (C 12 E 6 ), anionic sodium dodecylsulphate (SDS), cationic dodecyltrimethylammonium bromide (DTAB) and zwitterionic dodecylphosphocholine (C 12 PC) as model adjuvant systems to solubilise 3 pesticides, Cyprodinil (CP), Azoxystrobin (AZ) and Difenoconazole (DF), representing different structural features. The investigation focused on the influence of solubilisates in driving changes to the micellar nanostructures in the absence or presence of electrolytes. NMR and NOESY were applied to investigate the solubility and location of each pesticide in the micelles. SANS was used to reveal subtle changes to the micellar structures due to pesticide solubilisation with and without electrolytes., Findings: Unlike nonionic surfactants, the ionic and zwitterionic surfactant micellar structures remain unchanged upon pesticide solubilisation. Electrolytes slightly elongate the ionic surfactant micelles but have no effect on nonionic and zwitterionic surfactants. Pesticide solubilisation could alter the structures of the binary mixtures of ionic/zwitterionic and ionic/nonionic micelles by causing elongation, shell shrinkage and dehydration, with the exact alteration being determined by the molar ratio in the mixture., Competing Interests: Declaration of Competing Interest None., (Copyright © 2020. Published by Elsevier Inc.)

In spite of extensive research, it remains a formidable challenge to control the dimension of the nanostructures self-assembled from short designed peptides. In this work, we show that peptide bolaamphiphiles form monolayer wall nanotubes, facilitated by the interplay between the side chain structure and hydrophobicity of the central residues. The peptide KI 4 K self-assembles into nanotubes with a width of ~ 100 nm, but changes in the molecular structure of amino acid side chains could hugely impact the nanostructures formed. The three variants of KI 4 K, via the substitution of aromatic amino acids (F, Y, and Dopa) for the I residue closest to the C-terminus, could substantially reduce nanotube diameters, indicating a significant steric hindrance of the benzene rings on the lateral packing of β-sheets. However, the introduction of hydroxyl groups on the benzene rings alleviates the steric effect, with nanotube diameter increasing in the order of KI 3 FK, KI 3 YK, and KI 3 DopaK, suggesting the formation of side chain H-bonds between β-sheets in addition to hydrophobic contacts. Because the self-assembly process of KI 3 DopaK nanotubes is slow, key intermediates and their structural details are well characterized. With increasing incubation time, monolayered twisted ribbons and helical ribbons grow into mature KI 3 DopaK nanotubes via the pitch closing route., Competing Interests: Declaration of Competing Interest The authors have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Hypothesis: Surfactants are widely used in agri-sprays to improve pesticide efficiency, but the mechanism underlying their interactions with the surface wax film on plants remains poorly understood. To facilitate physical characterisations, we have reconstituted wheat cuticular wax films onto an optically flat silicon substrate with and without octadecyltrimethoxysilane modification to control surface hydrophobicity., Experiments: Imaging techniques including scanning electron microscopy (SEM) unravelled morphological features of the reconstituted wax films similar to those on leaves, showing little impact from the different substrates used. Neutron reflection (NR) established that reconstituted wax films were comprised of an underlying wax film decorated with top surface wax protrusions, a common feature irrespective of substrate hydrophobicity and highly consistent with what was observed from natural wax films. NR measurements, with the help of isotopic H/D substitutions to modify the scattering contributions of the wax and solvent, revealed different wax regimes within the wax films, illustrating the impact of surface hydrophilicity on the nanostructures within the wax films., Findings: It was observed from both spectroscopic ellipsometry and NR measurements that wax films formed on the hydrophobic substrate were more robust and durable against attack by nonionic surfactant C 12 E 6 solubilised with pesticide Cyprodinil (CP) than films coated on the bare hydrophilic silica. Thus, the former could be a more feasible model for studying the wax-surfactant-pesticide interactions., Competing Interests: Declaration of Interest Statement The current work is part of fundamental collaborative research carried out at the University of Manchester, with input from Syngenta and ISIS Neutron Facility at STFC. The funding support has been formally acknowledged. The authors have no conflict of interest., (Copyright © 2020. Published by Elsevier Inc.)

Hypothesis: Nonionic surfactants are used as adjuvants in agri-sprays to stabilise pesticides, but what happens when pesticide-loaded micelles are brought into direct contact with plant leaves? As pesticide solubilisation dehydrates the micellar shell and increases the effective hydrophobicity of the surfactant, we hypothesise that these micelles would uptake plant waxes and alter the amount of pesticide solubilized as a result of the re-equilibrating process., Experiments: The solubility of the pesticide cyprodinil (CP) and its effect on the shape of hexaethylene glycol monododecyl ether (C 12 E 6 ) micelles were studied using changes in cloud point, nuclear magnetic resonance (NMR), cryogenic transmission electron microscopy (Cryo-TEM) and small-angle neutron scattering (SANS). Similarly, the solubility of wheat leaf waxes was examined, as was the effect of adding leaf waxes to pre-dissolved cyprodinil in micellar C 12 E 6 ., Findings: Wax solubilisation caused pesticide release and shell hydration, and shortened the length of the cylindrical micelles of the CP loaded C 12 E 6 . Temperature increase led to a significant rise in the amount of the dissolved waxes, increased pesticide release, increased micellar length, and caused shrinkage and dehydration of the shell. This study indicates that agrochemical sprays are capable of dissolving leaf waxes, and may trigger pesticide release from surfactant micelles upon contact with plant surfaces., (Copyright © 2019. Published by Elsevier Inc.)

Nonionic surfactants have been widely used in agri-sprays to enhance the solubility and mobility of pesticides, but what happens when pesticides become solubilized into surfactant micelles remains poorly characterized. To facilitate physical characterisations, we used the nonionic surfactant hexaethylene glycol monododecyl ether (C 12 E 6 ) as a model system to solubilize 4 pesticides including Cyprodinil (CP), Diuron (DN), Azoxystrobin (AZ) and Difenoconazole (DF). The investigation focused on the influence of solubilizate and temperature in driving changes to the micellar nanostructures. Dynamic light scattering (DLS), cryogenic transmission electron microscopy (Cryo-TEM) and small-angle neutron scattering (SANS) measurements were used to reveal changes to the micellar structure before and after pesticide solubilisation. Nuclear magnetic resonance (NMR) was also applied to investigate the solubility and location of each pesticide in the micelles. Pesticides clearly altered the micellar structure, by increasing the aggregation number and micellar lengths, whilst shrinking and dehydrating the shells, leading to a consequent decrease in the dispersion cloud points. Increases in temperature affected micellar structures in a similar way. Thus, temperature increases and the solubilisation of pesticides can both make the surfactant effectively more hydrophobic, altering the micellar nanostructures and shifting the pesticide location within the micelles. These changes subsequently implicate how pesticides are delivered into plants through the natural wax films., (Copyright © 2019. Published by Elsevier Inc.)

Many short cationic peptides are amphiphilic and are often termed antimicrobial peptides (AMPs) as they can kill various microorganisms. These AMPs have largely been discovered from nature, but over the past two decades many biomimetic and de novo designed AMPs have been reported, offering a huge variety of attractive properties for further exploitation. Under the current global endeavour of fighting against antimicrobial resistance, it is useful to introduce AMPs to the biointerface research community and compare their modes of action with conventional antibiotics. Because natural AMPs often have long sequences and other biological functions implicated, they can't be used as antimicrobial agents. However, rational AMP design helps eliminate their shortcomings and more importantly, optimise their structure-function relationship. This review will first introduce the key approaches recently utilised in structural design of AMPs and then introduce the main lipid membrane models such as spread lipid monolayers and vesicles together with the characterisation techniques adopted in early AMP design and development. These studies are crucial towards understanding key factors affecting their efficacy and toxicity. Thus, various interfacial measurements facilitated by different forms of lipid monolayers and bilayers provide valuable support to the selective responses of AMPs to different cell types used in bactericidal assays and cytotoxicity tests, emphasising the link between molecular models and cell models. A number of clinical trials of AMPs have been either under way or completed, demonstrating the huge potential of AMPs in a range of applications., (Copyright © 2018. Published by Elsevier Inc.)