The development of neutron reflectivity for the study of surfaces and interfaces will be reviewed. The early stages of the development, the associated uncertainties, and the key breakthroughs associated with its application will be charted. Emphasis will be placed upon the importance of the ability to manipulate the refractive index by deuterium labelling, and the impact of this on our...
Recent development of antimicrobial peptides (AMPs) has focused on the rational design of short sequences with less than 20 amino acids due to their relatively low synthesis costs and ease of correlating structure-function relationship. However, there remain gaps in our understanding of how these short cationic AMPs interact with bacterial outer and inner membranes and how these interactions...
This work focuses on understanding interactions of polyphenolic compounds with model membrane systems. We selected a simple bacterial membrane model, a simple epithelial membrane model, and a complex epithelial membrane model (DOPC/DOPG (7:3), DOPC/DOPS (8:2), and DOPC/DOPS/Chol/SM (5:2:2:1) respectively). The interactions of these bilayers with three polyphenols, (-)-EGCg, Tellimagrandin I...
Maintaining the integrity of cellular lipid membranes is critical for proper functioning of cells. Many natural toxins have evolved to damage lipid membranes by forming pores. The mechanisms by which these pores are formed have been intensively studied in recent years because pore-forming proteins have a prominent role in microbial pathogenesis and the immune system. Biophysical and structural...
Antimicrobial peptides (AMPs) offer an alternative to currently used antibiotics. Because AMPs kill microbes by physically disrupting their membranes, the deactivation processes are usually faster and less likely to develop resistance. However, there are still many hurdles to be overcome before AMPs could be developed into medicinal uses. Current research challenges lie in understanding how to...
The genetic material of viruses is typically protected in an icosahedral capsid, which is primarily assembled from multiple subunits of the same protein in a spontaneous self-assembly process. Similar highly efficient assembly processes are ubiquitous in biological systems, and viral capsids in particular present a unique platform to exploit for therapeutic advances in the targeted cellular...
Nonionic surfactants are widely added into commercial pesticide formulation to help enhance pesticide solubilisation, increase droplet coverage on plant surface and transport active ingredients across plant “skin”, the wax film. However, our current knowledge of these interactions at the molecular level still remains very limited. As a result, little is known about how these interactions...
Early models of the gram-negative bacterial membrane tended to focus on replicating the negative charge of the system. This approach was rather simplistic and didn’t consider either the overall structural or molecular complexity of the membrane. In recent years, while the structural complexity is still challenging, progress has been made at increasing the molecular complexity of model...
Surface-sensitive scattering of x-rays or neutrons has long been used to characterize the molecular scale properties of lipid monolayers and bilayers at aqueous surfaces and interfaces,[1,2] but has not been in the standard toolbox for structural biology due to several limitations. Most seriously, the intrinsic resolution of reflectometry in its application to biological membranes is far less...
Our research focuses on developing platforms for studying complex proteinaceous machineries at the solid liquid interface. In this talk I will discuss our advances in the incorporation of active proteinaceous machineries within planar lipid bilayers. How through the use of floating supported bilayers we can tune the distance of these complexes from the surface through solution electrolyte...
The insertion of peptides and proteins into cell membranes is crucial for a huge range of biological functions and has been widely studied. However, real biological membranes are subject to continuous attack by oxidants, changing their chemical composition, structure and biophysical properties. We have used neutron reflection as a tool to study how oxidation changes the structure of both...
The metabolism of fats including lipids and cholesterol involves the production, in the liver, of lipid carrying particles known as lipoproteins. Lipoproteins are nanoemulsion-like particles composed of fats and proteins (named apolipoproteins). The complexity of lipoproteins is great, with different compositions not only in terms of the amounts of the fat and proteic components, but also on...
Epidemic thunderstorm asthma triggered by the unique combination of grass pollens and thunderstorm activity affects a large population within a local vicinity.$^1$ The inhalation of a high load of respirable aeroallergen proteins released under the influence of a storm has been associated with asthma exacerbation.$^2$ Particularly, the biophysical interactions of such allergens with the lung...
Resolving structural and functional aspects of interactions between proteins and membranes requires experiments on membranes which mimic cellular characteristics as closely as possible. In this respect, previous methods which tethered or bound the membrane to a subjacent substrate showed significant deficiency. However, the so-called free-floating bilayer (FFB) model membrane system promises...
KRas4B is a membrane-anchored signaling protein and a primary target in cancer research. Predictions from molecular dynamics simulations have shaped our mechanistic understanding of KRas signaling but disagree with recent experimental results from neutron reflectometry [1]. Therefore, we implemented restrained and bias-free molecular simulations for a quantitative comparison with NR and...
Rising antimicrobial resistance represents an ongoing global challenge. Antimicrobial peptides have shown promise in overcoming some of the limitations of traditional small molecule antimicrobials, where resistance can be typically easily acquired, yet can still be targeted by secreted proteases, typically display high cytotoxicity against mammalian cells and are synthetically expensive to...
Gram-negative bacteria are surrounded by a protective outer membrane with phospholipids in its inner leaflet and lipopolysaccharides (LPS) in its outer leaflet. The outer membrane is also populated with many β-barrel outer-membrane proteins (OMPs), some of which have been shown to cluster into supramolecular assemblies. Using atomic force microscopy on living bacteria, we have shown that the...
[1]Investigating model influence on the analytical resolution of neutron
reflectometry
Neutron reflectometry is an invaluable tool for the study of biological samples due to its sensitivity to atomic nuclei and their penetrative capabilities [2] [3] [4]. The resolution of the technique as de-fined by the diffraction limit is at about 10 Å. However, evidence from literature would suggest...
One of the most abundant proteins in gram-negative bacterial membrane is outer membrane protein F (OmpF). In recent years the mechanisms of OmpF interaction with antimicrobial agents and other membrane components were actively investigated [1-4]. This research demonstrated that OmpF has a substantial potential in the number of biotechnology applications such as vaccines and biosensor...
When I belatedly started using neutrons in my career my research interests included the Gram negative outer membrane (OM) and surface bound proteins. Both leant well to NR research and since then I have been helped by supportive colleagues to answer some fundamental questions about my research areas. These include the structure of the OM, its dynamics and interactions with proteins and...
2022 marks the 90th anniversary of the Nobel prize awarded to Irwin Langmuir for his seminal work on surface chemistry, which remains to this day a central pillar of interface science. An example of his lasting legacy are the insoluble monolayers that bear his name and their many applications in biological membrane research. Langmuir monolayers represent versatile building blocks to assemble...
Antimicrobial peptides (AMPs) are characterized as small, cationic peptides which, as the name suggests, show antimicrobial properties; something that has received considerable attention in recent years. These peptides can, according to structure, be classified into four different groups: extended AMPs, -hairpin or loops, -sheet, and amphipathic -helical [1-2]. In this work the focus is...
Biophysical and structural studies of peptide-lipid interactions, peptide topology and dynamics have changed our view how antimicrobial peptides insert and interact with membranes. Clearly, both the peptides and the lipids are highly dynamic, change and mutually adapt their conformation, membrane penetration and detailed morphology on a local and a global level. As a consequence, the peptides...
Programmed cell death (apoptosis) is essential for human life. In its intrinsic apoptotic pathway opposing members of the B-cell lymphoma 2 (Bcl-2) protein family control the permeability of the mitochondrial outer membrane (MOM) and any release of apoptotic factors. Any imbalance can cause disorders including cancer, where often upregulation of cell protecting (anti-apoptotic) Bcl-2 members...
Classical molecular dynamics (MD) provides atomic level detail on the structure and dynamics of biological molecules, as well as allowing in silico experiments on the system of interest. In particular, MD has been applied to biological membranes where historically there has been a lack of high resolution experimental probes. There are now increasing efforts to combine the level of detail...
Reflectivity data is traditionally analysed using simple, layered approximations of the interface. Whilst these give a guide to the structure, fine details of the interface are often unresolved. Over the past 20 years, there has been a move to using more sophisticated models, using information from atomistic simulations to construct more refined descriptions of the interface. We have recently...
The resolution revolution in cryo electron microscopy, led by the introduction of direct electron detectors, has let to unprecedent gains in structural biology. However, despite advances in data collection and image processing, single particle cryoEM of small proteins, in particular small membrane proteins remains a challenge.
The Membrane Protein Laboratory at Diamond Light Source is funded...
Neutron reflectometry (NR) is an ideal tool for studying biological membrane models, and many different models, mimicking bacterial and mammalian cells have been developed in recent years. Often, the focus of such NR studies is on the interaction of various molecules, e.g. proteins, polymers, peptides etc with the membrane model. Another interesting use of such models is the characterisation...
