Jonathan P. Bramble

Biotemplated magnetic nanoparticle arrays

Immobilized biomineralizing protein Mms6 templates the formation of uniform magnetite nanoparticles in situ when selectively patterned onto a surface. Magnetic force microscopy shows that the stable magnetite particles maintain their magnetic orientation at room temperature, and may be exchange coupled. This precision-mixed biomimetic/soft-lithography methodology offers great potential for the future of nanodevice fabrication.

Arp2/3 complex activity in filopodia of spreading cells

BackgroundCells use filopodia to explore their environment and to form new adhesion contacts for motility and spreading. The Arp2/3 complex has been implicated in lamellipodial actin assembly as a major nucleator of new actin filaments in branched networks. The interplay between filopodial and lamellipodial protrusions is an area of much interest as it is thought to be a key determinant of how cells make motility choices.ResultsWe find that Arp2/3 complex localises to dynamic puncta in filopodia as well as lamellipodia of spreading cells. Arp2/3 complex spots do not appear to depend on local adhesion or on microtubules for their localisation but their inclusion in filopodia or lamellipodia depends on the activity of the small GTPase Rac1. Arp2/3 complex spots in filopodia are capable of incorporating monomeric actin, suggesting the presence of available filament barbed ends for polymerisation. Arp2/3 complex in filopodia co-localises with lamellipodial proteins such as capping protein and cortactin. The dynamics of Arp2/3 complex puncta suggests that they are moving bi-directionally along the length of filopodia and that they may be regions of lamellipodial activity within the filopodia.ConclusionWe suggest that filopodia of spreading cells have regions of lamellipodial activity and that this activity affects the morphology and movement of filopodia. Our work has implications for how we understand the interplay between lamellipodia and filopodia and for how actin networks are generated spatially in cells.

Innovation through imitation: biomimetic, bioinspired and biokleptic research

While biomimetic research is becoming increasingly popular the term is being used for a broader range of research and it is becoming more difficult for researchers to understand and define. In this opinion article we discuss how biomimetic research overlaps with and differs from the complementary fields of biotechnology, biokleptic and bioinspired research as we attempt to describe each area with definitions, examples and discussion. What makes research biomimetic, bioinspired or biokleptic is put under scrutiny as we ask: can different components, parts and processes of an experiment be categorised separately? What is the difference between a biological and synthetic system/component? Is the scientist or biology in control? The answers to which aim to untangle the subtleties of the biomimetics field.

Self-assembled MmsF proteinosomes control magnetite nanoparticle formation in vitro

Significance Magnetotactic bacteria produce morphologically precise magnetite nanoparticles within organelles termed “magnetosomes.” Biomineralization proteins tightly regulate crystallization of these nanoparticles. A master protein regulator of particle morphology in vivo, magnetosome membrane specific F (MmsF), has recently been discovered. In this study, we purified MmsF and two homologous proteins from Magnetospirillum magneticum strain AMB-1. MmsF imposes strict control over the formation of magnetite nanoparticles when added to chemical precipitation reactions, whereas the highly similar homologues produce alternative iron oxides with less desirable magnetic properties. Remarkably, these intrinsic membrane proteins with three membrane-spanning regions are water-soluble and self-assemble in vitro into nanoscale “proteinosomes.” We speculate that self-assembly exists in vivo and might be required for the activity of the protein. Magnetotactic bacteria synthesize highly uniform intracellular magnetite nanoparticles through the action of several key biomineralization proteins. These proteins are present in a unique lipid-bound organelle (the magnetosome) that functions as a nanosized reactor in which the particle is formed. A master regulator protein of nanoparticle formation, magnetosome membrane specific F (MmsF), was recently discovered. This predicted integral membrane protein is essential for controlling the monodispersity of the nanoparticles in Magnetospirillum magneticum strain AMB-1. Two MmsF homologs sharing over 60% sequence identity, but showing no apparent impact on particle formation, were also identified in the same organism. We have cloned, expressed, and used these three purified proteins as additives in synthetic magnetite precipitation reactions. Remarkably, these predominantly α-helical membrane spanning proteins are unusually highly stable and water-soluble because they self-assemble into spherical aggregates with an average diameter of 36 nm. The MmsF assembly appears to be responsible for a profound level of control over particle size and iron oxide (magnetite) homogeneity in chemical precipitation reactions, consistent with its indicated role in vivo. The assemblies of its two homologous proteins produce imprecise various iron oxide materials, which is a striking difference for proteins that are so similar to MmsF both in sequence and hierarchical structure. These findings show MmsF is a significant, previously undiscovered, protein additive for precision magnetite nanoparticle production. Furthermore, the self-assembly of these proteins into discrete, soluble, and functional “proteinosome” structures could lead to advances in fields ranging from membrane protein production to drug delivery applications.

Nanomagnetic Arrays Formed with the Biomineralization Protein Mms6

Many Modern Technologies, such as High Density Data Storage, Require Monodispersed Magnetic Nanoparticles (MNPs), which Have a Consistent Magnetic Behavior, Specifically Immobilized onto a Patterned Surface. Current Methods for Synthesizing Uniform Mnps Require High Temperatures and Harsh Chemicals, which Is Not Environmentally Friendly. Also, the Particles Are Expensive to Make and Expensive to Pattern Using Conventional Lithography Methods. Magnetic Bacteria Are Able to Synthesize Consistent Mnps in Vivo Using Biomineralization Proteins inside Magnetosome Vesicles to Control Particle Size and Shape and Make Single Domain Mnps. Mms6 Is a Biomineralization Protein that Is Able to Template Cubo-Octahedral MNP Formation in Vitro. it Is Thought the N-Terminus Helps Integrate the Protein into the Magnetosome Membrane, and the C-Terminus Interacts with Magnetite during Nucleation and/or MNP Growth. by Selectively Attaching Mms6 to a Patterned Self Assembled Monolayer via the N-Terminus, Patterns of Uniform Magnetite Mnps Are Templated in Situ. this Also Requires Careful Selection of the Mineralization Solution Used to Mineralize the Patterned Mms6. here we Evaluate some Low Temperature (room Temperature to < 100°C) Methods of Magnetite Formation to Produce Monodispersed Magnetite Mnps onto Immobilized Mms6. Room Temperature Co-Precipitation (RTCP) Was Found to Be Unsuitable, as the Magnetite Does Not Form on the Immobilized Mms6, but Appears to Form Rapidly as Base Is Added. Partial Oxidation of Ferrous Hydroxide (POFH) Was Found to Be Able to Form Consistent Magnetite Mnps on the Immobilized Mms6, as the Reactants Gradually Mature to Form Magnetite over a few Hours (at 80°C) or a few Days (room Temperature). by Carefully Controlling the Type of Base Used, the Ratio of the Reactants and the Temperature and Duration of the POFH Mineralization Reaction, this System Was Optimized to Produce Consistent Mnps (340 ± 54 Nm, Coercivity 109 Oe) on the Immobilized Mms6, with Scarcely any Mineralization on the Anti-Biofouling Background. the Mnps Are Ferrimagnetic, and Appear to Be Exchange Coupled across Multiple Particles in MFM Measurements. the Specificity of this Method towards Precise Magnetite Mineralization under Relatively Mild Conditions May Be Adapted to Nanoscale Patterning of Multiple Biotemplated Materials, by Using other Biomineralization Proteins or Peptides. this Would Allow the Fabrication of Cheaper, More Environmentally Friendly Components for Devices of the Future.

Controlling Liquid Crystal Alignment Using Photocleavable Cyanobiphenyl Self-Assembled Monolayers

We report on the development of novel cyano-biphenyl-based thiolate self-assembled monolayers designed to promote homeotropic alignment of calamitic liquid crystals. The molecules developed contain an ortho-nitrobenzyl protected carboxylic acid group that on irradiation by soft UV (365 nm) is cleaved to yield carboxylic acid groups exposed at the surface that promote planar alignment. Using a combination of wetting, X-ray photoelectron spectroscopy, Fourier transform-infrared reflection absorption spectroscopy, and ellipsometry we show that high photolysis yields (>90%) can be achieved and that the patterned SAMs are suitable for the controlled alignment of calamitic liquid crystals. This study further shows that such photo-patterned SAMs can be used to control the formation of focal conic domains (FCDs) in the smectic-A phase in terms of positioning and size confinement on surfaces.

Biomimetic Synthesis of Materials for Technology

In a world with ever decreasing natural reserves, researchers are striving to find sustainable methods of producing components for technology. Bioinspired, biokleptic and biomimetic materials can be used to form a wide range of technologically relevant materials under environmentally friendly conditions. Here we investigate a range of biotemplated and bioinspired materials that can be used to develop components for devices, such as optics, photonics, photovoltaics, circuits and data storage.

Nematic liquid crystal alignment on chemical patterns

Patterned Self‐Assembled Monolayers (SAMs) promoting both homeotropic and planar degenerate alignment of 6CB and 9CB in their nematic phase were created using microcontact printing of functionalized organothiols on gold films. The effects of a range of different pattern geometries and sizes were investigated, including stripes, circles and checkerboards. Evanescent wave ellipsometry was used to study the orientation of the liquid crystal (LC) on these patterned surfaces during the isotropic‐nematic phase transition. Pretransitional growth of a homeotropic layer was observed on 1 µm homeotropic aligning stripes, followed by a homeotropic monodomain state prior to the bulk phase transition. Accompanying Monte Carlo simulations of LCs aligned on nanoscale‐patterned surfaces were also performed. These simulations also showed the presence of the homeotropic monodomain state prior to the transition.

Ferrous Iron Binding Key to Mms6 Magnetite Biomineralisation: A Mechanistic Study to Understand Magnetite Formation Using pH Titration and NMR Spectroscopy.

Abstract Formation of magnetite nanocrystals by magnetotactic bacteria is controlled by specific proteins which regulate the particles’ nucleation and growth. One such protein is Mms6. This small, amphiphilic protein can self‐assemble and bind ferric ions to aid in magnetite formation. To understand the role of Mms6 during in vitro iron oxide precipitation we have performed in situ pH titrations. We find Mms6 has little effect during ferric salt precipitation, but exerts greatest influence during the incorporation of ferrous ions and conversion of this salt to mixed‐valence iron minerals, suggesting Mms6 has a hitherto unrecorded ferrous iron interacting property which promotes the formation of magnetite in ferrous‐rich solutions. We show ferrous binding to the DEEVE motif within the C‐terminal region of Mms6 by NMR spectroscopy, and model these binding events using molecular simulations. We conclude that Mms6 functions as a magnetite nucleating protein under conditions where ferrous ions predominate.

Observations of focal conic domains in smectic liquid crystals aligned on patterned self‐assembled monolayers

Patterned Self‐Assembled Monolayers (SAMs) promoting both homeotropic and planar degenerate alignment of nCBs in their smectic‐A phase were created using microcontact printing of functionalized organothiols on gold films. By patterning the surface with homeotropic and planar aligning SAMs, the location and formation of the focal conic domains (FCDs) can be controlled. Polarizing microscopy was used to study the formation of FCDs in circle, stripe and checkerboard pattern geometries. Fluorescent confocal microscopy (FCM) was used for the first time to measure the eccentricity of FCDs that form along a stripe pattern.