pH DEPENDENCE OF LIPID MEDIATED AMR IN MODEL STAPHYLOCOCCAL PLASMA MEMBRANES
R. Rehal, P.R. J. Gaffney, A.T. M. Hubbard, R.D. Barker & R.D. Harvey
The role of LPG in resistance to human epithelial defences in S. aureus and the continued evolution of this opportunistic pathogen’s virulence are investigated using synthetic biomimetic mono- and bilayer models of methicillin resistant S. aureus based on its lipid composition in both pH 7.4 (28% LPG) and pH 5.5 (51% LPG) cultures.
TOWARDS BIOMIMICS OF CELL MEMBRANES: STRUCTURAL EFFECT OF PIP3 ON LIPID BILAYERS
A. Luchini, A.N.O. Nzulumikea, T.K. Lind, T. Nylander, R. Barker, L. Arleth, K. Mortensen & M. Cárdenas
Phosphoinositide (PIP) lipids are anionic phospholipids playing a fundamental role for the activity of several transmembrane and soluble proteins. This study reveals the (thus far unexplored) structure of PIP-containing membranes, combining QCM-D, AFM & neutron reflectometry. Results support PIP3 tendency to interact with the bilayer lipid head groups.
IN-SITU DYNAMIC SUB-SURFACE IMAGING OF MULTI-COMPONENT ELECTRODEPOSITED FILMS
A.R. Hillman, R. Barker, R.M. Dalgliesh, V.C. Ferreira, E.J.R. Palin, R.M. Sapstead, E.L. Smith, N.-J. Steinke, K.S. Ryder & A.D. Ballantyne
Control of the electrodeposition of metal films & coatings is critical to many high technology & manufacturing industries, delivering functionality as anti-corrosion & anti-wear coatings, electronic device interconnects & energy storage. Here we demonstrate a combined QCM & neutron reflectivity approach to probe the deposition of these coatings in real-time.
INFLUENCE OF SURFACTANT STRUCTURE ON
π-CONJUGATED POLYMER NANOPARTICLES
L. Urbano, L.A. Clifton, H.K. Ku, H.Kendall-Troughton, K.-K.A. Vandera, B.F.E. Matarèse, T. Abelha, P. Li, T.A. Desai, C.A. Dreiss, R.D. Barker, M.A. Green, LA. Dailey & R.D. Harvey
π-Conjugated polymer nanoparticles (CPNs) are of interest as photoluminescent agents for diagnostics and bioimaging. To determine whether the choice of surfactant can improve CPN properties and prevent protein adsorption, five nonionic polyethylene glycol alkyl ether surfactants were used to produce CPNs from three representative π-conjugated polymers.
TIME-RESOLVED ELECTROCHEMICAL DEPOSITION OF Ag & Cu FROM DEEP EUTECTIC SOLVENTS
A.D. Ballantyne, R. Barker, R.M. Dalgliesh, V.C. Ferreira, A.R. Hillman, E.J.R. Palin, R. Sapstead, E.L. Smith, N.-J. Steinke & K.S. Ryder
Real-time analysis of electrodeposited metal films using neutron reflectivity methods is demonstrated here for the first time with comparison of approaches to data analysis. These data show that the different electrochemical growth methodologies exhibit different trends in thickness, roughness and solvation, which can be followed in real-time.
EFFECT OF BILAYER CHARGE ON LIPOPROTEIN LIPID EXCHANGE
K. Browning, T.K. Lind, S. Maric, R. Barker, M. Cárdenas & M. Malmsten
High & low density lipoproteins are of particular interest in relation to atherosclerosis, due to their respective protective and harmful effects. Here is the biophysical molecular mechanisms underlying this are investigated, to identify factors (particularly membrane charge density) determining lipid deposition and exchange at the membrane interface.
NANO-IN-NANO APPROACH FOR IMMOBILIZING ENZYMES BASED ON BLOCK COPOLYMERS
F. Auriemma, C. De Rosa, A. Malafronte, R. Di Girolamo, C. Santillo, Y. Gerelli, G. Fragneto, R. Barker, V. Pavone, O. Maglio & A. Lombardi
Here we demonstrate block copolymers self-assembly, used to prepare nanostructured thin films with well-defined architecture containing pores of tailorable size delimited by walls with tailorable degree of hydrophilicity, designed for immobilization of enzymes.
NEUTRON REFLECTIVITY & PERFORMANCE OF POLYAMIDE NANOFILMS IN WATER DESALINATION
F. Foglia, S. Karan, M. Nania, Z. Jiang, A.E. Porter, R. Barker, A.G. Livingston & J.T. Cabral
Polyamide membranes synthesized by the interfacial polymerisation of phenylenediamine and trimesoyl chloride, varying conditions systematically were characterised structurally and their performance in reverse osmosis water desalination benchmarked. This gives insight into the film formation mechanisms & correlates reaction conditions to performance.
STRUCTURAL VARIATIONS IN HYBRID CELLULOSE NANOCRYSTAL / GIBBSITE MULTILAYERED FILMS
C. Martin, R.D. Barker, E.B. Watkins, F. Dubreuil, E.D. Cranston, L. Heux & B. Jean
Cellulose nanocrystals (CNCs) are promising biosourced building blocks for the production of high performance materials. Here we demonstrate the formation of hybrid composite films from CNCs & charged inorganic gibbsite nanoplatelets. The degree of structural control over this new class of films is much greater than any others previously reported.
MEMBRANE ASSOCIATION OF MBP PORTRAYS FORMATION OF MYELIN MAJOR DENSE LINE
A. Raasakka, S. Ruskamo, J. Kowal, R. Barker, A. Baumann, A. Martel, J.Tuusa, M. Myllykoski, J. Bürck, A.S. Ulrich, H. Stahlberg & P. Kursula Scientific Reports (2017) 7:4974
Myelin basic protein (MBP) is an abundant myelin protein involved in demyelinating diseases, such as multiple sclerosis. Here we employed biophysical methods to investigate the role of MBP in the formation of membrane stacks from a single leaflet to the full major dense line and use this as a model to start understanding demyelinating conditions.
MECHANISM OF ACTION OF A QUINOLINE-BASED ANTIMICROBIAL ON BACTERIAL MEMBRANES
A.T.M. Hubbard, R.D. Barker, R.P. Rehal, K.-K.A. Vandera, R.D. Harvey & A.R.M. Coates
HT61 is a quinoline-derived antimicrobial, which exhibits bactericidal potency against MRSA and has been proposed as an adjunct for other antimicrobials in the face of increasing AMR. In this study we examine HT61’s effect on the permeability of Staph. aureus membranes and whether this putative activity can be attributed to an interaction with lipid bilayers.
GRAVIMETRIC & DENSITY PROFILING WITH SURFACE ACOUSTIC WAVES & NEUTRON REFLECTIVITY
D.T.W. Toolan, R.D. Barker, T. Gough, P.D. Topham, J.R. Howse & A. Glidle
This is the 1st ever demonstration combining neutron reflectivity measurements, that probe changes in the density profile of thin films as they absorb material, combined with a Love wave based gravimetric assay that measures the mass of absorbed material. This paper explores the limitations, potential & future applications of this novel approach.
EXCHANGE IN STYRENE MALEIC ACID LIPID PARTICLE (SMALP) NANODISC SYSTEMS
G. Hazell, T. Arnold, R.D. Barker, L.A. Clifton, N.-J. Steinke, C. Tognoloni & K.J. Edler
SMALPs are self-assembled discoidal structures composed of a polymer belt and a lipid bilayer, capable of encapsulating membrane proteins directly from the cell membrane. Here we show the exchange of lipids between SMALPs and lipid monolayers adsorbed at either solid or air−liquid interfaces, an important implication for the potential uses of nanodiscs.
BIOPHYSICAL STUDY OF RESIN ACID EFFECTS ON LIPID MEMBRANE STRUCTURE & PROPERTIES
V. Jagalski, R. Barker, D. Topgaard, T. Günther Pomorski, B. Hamberger & M. Cárdenas
Hydrophobic resin acids (RAs) are synthesized by conifer trees as part of their defense mechanisms. One of the functions of RAs in plant defense is suggested to be the perturbation of the cellular membrane. In this study, we unravel the molecular interactions of 3 closely related RAs, correlating their physical chemical properties & toxicity with membrane effects.
LIPIDATION EFFECT ON SURFACE ADSORPTION & ASSOCIATED FIBRILLATION OF INSULIN
S.F. Hedegaard, M. Cárdenas, R. Barker, L. Jorgensen & M. van de Weert
We investigate the effect of a 14-carbon fatty acid modification on the adsorption behavior of human insulin to a hydrophobic solid surface. The subsequent fibrillation development under highly acidic conditions and elevated temperature was time resolved and compared to the fibrillation of human insulin using AFM, QCM-D & neutron reflectivity.
DISCERNING THE STRUCTURE OF FIBRINOGEN ADSORBED AT THE STAINLESS STEEL INTERFACE
M.H. Wood, K.L. Browning, R.D. Barker & S.W. Clarke
Neutron reflectometry has been successfully used to study adsorption on a stainless steel surface by depositing a thin steel film on silicon. The protein was found to form an irreversibly bound layer at low conc., with max. protein conc. at ~20 Å from the surface. Evidence for a further diffuse reversibly-bound layer forming at higher concs. was seen.
THE EFFECT OF UREA & TAURINE AS PENETRATION ENHANCERS ON STRATUM CORNEUM LIPID MODELS
J. Mueller, J.S.L. Oliveira, R. Barker, M. Trapp, A. Schroeter, G. Brezesinski & R.H. Neubert
To optimize transdermal application of drugs, the barrier function of the skin, especially the stratum corneum (SC), needs to be reduced reversibly by penetration enhancers like urea or taurine are applied. This study investigates if this enhancement is caused by an interaction with the SC lipid matrix or related to effects within the corneocytes.
NEUTRON REFLECTIVITY AS A TOOL FOR PHYSICS-BASED STUDIES OF MODEL BACTERIAL MEMBRANES
R. Barker, L.E. McKinley & S. Titmuss
Controlled composition bilayers can now be constructed, facilitating studies ranging from characterising fundamental physical interactions, to accurate mimetics for the inner & outer membranes of Gram-negative bacteria. The principles of neutron reflectivity and its use to provide structural information at sub-molecular length scales from these models is discussed.
THE INFLUENCE OF ROUGH LPS STRUCTURE ON INTERACTIONS WITH ANTIMICROBIAL PEPTIDES
G. Bello, A. Bodin, M.J. Lawrence, D. Barlow, A.J. Mason, R.D. Barker & R. D. Harvey
The influence of Escherichia coli rough lipopolysaccharide chemotype on the membrane activity of the mammalian antimicrobial peptides (AMPs) human cathelicidin (LL37) and bovine lactoferricin (LFb) was studied on bilayers using a suite of biophysical techniques. Evidence for the molecular origins of the AMPs different biological activities is explored.
IMPROVED ALGORITHM FOR REDUCING NEUTRON REFLECTIVITY DATA WITH DIVERGENT BEAMS
R. Cubitt, T. Saerbeck, R.A. Campbell, R. Barker & P. Gutfreund
Reflectometry is a powerful technique for determining physical quantities of stratified media. However, experimentally neutron reflectometry suffers from the relatively feeble brilliance of the sources compared with those of X-rays. Here we present a method for substantial gains in statistical quality, equivalent to a significant flux increase, alongside improved resolution.
GRAFTED BIOMEMBRANES CONTAINING MEMBRANE PROTEINS - LEUCINE TRANSPORTER CASESTUDY
V. Jagalski, R.D. Barker, M.B. Thygesen, K. Gotfryd, M.B. Krüger, L. Shi, S. Maric, N. Bovet, M. Moulin, M. Haertlein, T.G. Pomorski, C.J. Loland & M. Cárdenas
We present a new method for the capture and study of membrane proteins by binding the sodium dependent amino acid transporter on NTA/PEG functionalised gold sensors. We characterise the LeuT structure in the adsorbed film by magnetic contrast neutron reflection using the predicted model from molecular dynamic simulations. Bridging between MD & NR.
NANODISC FILMS FOR MEMBRANE PROTEIN STUDIES BY NEUTRON REFLECTION
N. Bertram, T. Laursen, R. Barker, K. Bavishi, B.L. Møller & M. Cárdenas
Nanodisc films are a promising approach to study the equilibrium conformation of membrane bound proteins in native-like environment. Here we compare nanodisc formation for NADPH-dependent cytochrome P450 oxidoreductase (POR) using two different sizes of scaffold proteins. The results indicate that the smaller discs are better for NR studies.
IS OSMOTIC PRESSURE RELEVANT IN THE DIRECT CONFINEMENT OF A POLYMER BRUSH?
S.B. Abbott, W.M. de Vos, L.L.E. Mears, B. Cattoz, M.W.A. Skoda, R. Barker, R.M. Richardson & S.W. Prescott
The structures of polymer brushes under confinement were measured using a combination of neutron reflectivity and a surface force type apparatus. These experimental results are compared against a theoretical model based on numerical self-consistent field (nSCF) theory as well as to osmotic, SFA, and AFM data. Significant differences were found and discussed.
INTERACTION OF MORINGA OLEIFERA SEED PROTEIN WITH MINERAL SURFACE & SURFACTANTS
H.M. Kwaambwa, M.S. Hellsing, A.R. Rennie & R. Barker
Neutron reflection was used to determine the structure and composition of interfacial layers adsorbed at the solid/liquid interface of purified protein from seeds of Moringa Oleifera to a sapphire interface & the effects of addition of the anionic SDS and the cationic surfactant CTAB. The different responses could be used in water separation technologies.
ANALYSIS OF BIOSURFACES BY NEUTRON REFLECTOMETRY: FROM SIMPLE TO COMPLEX
A. Junghans, E.B. Watkins, R.D. Barker, S. Singh, M.J. Waltman, H.L. Smith, L. Pocivavsek & J. Majewski
Over the past two decades, Neutron Reflectometry has evolved to become a key tool in the characterization of biological and biomimetic thin films. In this report, we highlight some of our recent accomplishments in utilising NR to study highly complex systems, including in-situ experiments. Particularly the application of electrochemistry to biological membranes.
PAPERS FROM BEFORE 2015 COMING SOON...
R.D. Barker et al.
These will be added when Rob has a few spare minutes!!
Until then, our complete list of publications can be found on ResearchGate.