Contact us: s.mann@bristol.ac.uk

Titles and Abstracts of Recent Talks

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Professor Stephen Mann FRS,
School of Chemistry
University of Bristol
Bristol
BS8 1TS, UK

Tel: 0044 (0)117-9289935
s.mann@bristol.ac.uk

Material Futures: Towards Synthetic Cellularity via Protocell Design and Construction 

The design and construction of compartmentalized materials ensembles for modelling complex biological systems, exploring the origin of life, and advancing future living technologies is attracting considerable interest in a wide range of research communities. In this talk, I will review some recent experiments undertaken in my laboratory that provide steps towards synthetic cellularity using bioinspired materials chemistry principles and techniques. I will discuss four new protocell models based on; (i) nanoparticle self-assembly (colloidosomes) [1], (ii) interfacial assembly of protein-polymer nanoconjugates (proteinosomes) [2], (iii) micro-droplet formation (coacervation) [3,4], and hybrids of the above [5]. I will use these new model systems to discuss pathways towards chemical cognition, modulated reactivity, basic signalling pathways and non-equilibrium activation in compartmentalized artificial micro-ensembles.

References:

[1]. Li M et al., Membrane-gated permeability in self-activated inorganic protocells. Nature Chem., 5, 529-536 (2013).

[2]. Huang X, et al., Interfacial assembly of protein-polymer nano-conjugates into stimulus-responsive biomimetic protocells. Nature Commun. 4, 2239 (2013) DOI: 10.1038/ncomms 3239, 1-9 (2013).

[3] Koga, S., et al., Peptide–nucleotide microdroplets as a step towards a membrane-free protocell model. Nature Chem. 3, 720-724 (2011).

[4] Yin Y, et al., Non-equilibrium behaviour in coacervate-based protocells under electric field-induced excitation. Nature Commun. 7, 10658, 1-7 (2016); DOI:10.1038/ncomms10658 1-7 (2016).

[5] Tang T-Y D, et al., Fatty acid membrane assembly on coacervate micro-droplets as a step towards a hybrid protocell model. Nature Chem. 6, 527- 533 (2014).

ETH, Zurich (2016)


Soft Matter Chemistry at the Proto-life/Synthetic Biology Interface

The fundamental understanding of living systems as an integrated network of functional compartments and components serves as a powerful paradigm in the bio-inspired synthesis and design of novel soft structures and processes. Such an approach not only provides an expanding platform of new materials for specific applications, but also inspires advances in soft matter chemistry at the interface of synthetic biology and protocell modelling. In this talk, I review some recent studies undertaken in my laboratory that address the interface between proto-life research and synthetic biology. Two themes will be considered. Firstly, can proteins with biomimetic potential maintain their structure and function in the absence of water (or any other solvent) whilst retained in the liquid state? And secondly, can protocell models be constructed based on bioinspired materials design and construction? Specifically, I will describe our current studies on the first known examples of solvent-less liquid proteins, including studies on the dioxygen binding and temperature-dependent chain unfolding properties of liquid myoglobin. Then I will discuss our recent investigations on artificial protocells that are derived from organic self-assembly, nanoparticle-based membrane assembly or membrane-free condensed microdroplets, and illustrate respectively how such structures can be used to accommodate primitive cytoskeletal-like hydrogels, as bio-inorganic nanoparticle-based reactors for enzyme catalysis and in vitro gene expression, or as a plausible micro-droplet model of pre-biotic organization.


New paradigms at the proto-life/synthetic biology interface

The advent of life from pre-biotic origins remains a deep and possibly inexplicable scientific mystery. Nevertheless, the logic of living cells offers potential insights into an unknown proto-biological world that can be used to stimulate novel advances in living technologies, artificial life and systems chemistry. In this talk, I will review some recent studies undertaken in our laboratory that provide alternative paradigms at the interface between proto-life research and synthetic biology. Two themes will be addressed (somewhat obliquely!). Firstly, can proteins maintain their structure and function in the absence of water (or any other solvent) whilst retained in the liquid state? And secondly, can protocell models be constructed without an enclosing organic membrane? Specifically, I will describe our current studies on the first known examples of solvent-less liquid proteins, including studies on the dioxygen binding and temperature-dependent chain unfolding properties of liquid myoglobin. Then I will discuss our recent investigations on artificial protocells that are derived from inorganic or membrane-free compartmentalization, and illustrate respectively how such structures can be used as bio-inorganic reactors for enzyme catalysis and in vitro gene expression, or as a plausible model of pre-biotic organization.


Synthesis, emergence and new properties of hybrid nanoscale objects

Organized-matter chemistry is concerned with the synthesis, characterization and application of complex materials that exhibit order on length scales from the molecular to macroscopic. Recently, new strategies have been developed for the integration of organic self-organization and inorganic assembly such that hybrid nanoscale objects and nanostructures can be constructed by equilibrium (bottom-up templating) or non-equilibrium processes (synergistic emergence) [1]. These principles will be illustrated using several examples of our most recent work including the co-assembly of block copolymer/titania [2] or polymer/silica nanowires [3], synthesis of metallic nanowires arrays within cross-linked protein crystals [4], reconstitutive co-assembly of graphene/DNA nano-hybrids [5] and the unprecedented formation of solventless liquid proteins at room temperature [6,7].


Biomineral-inspired Synthesis and Self-assembly of Nanoparticle Arrays and Nanostructured Materials.

Organized-matter chemistry is concerned with the synthesis, characterization and application of complex materials that exhibit order on length scales from the molecular to macroscopic. Recently, new strategies have been developed for the synthesis of organized inorganic nanostructures based on biomolecular templates, facilitated self-assembly of nanoparticle building blocks, and mesoscale transformations in complex fluids. A key aspect of this approach is the integration of organic self-organization and inorganic assembly such that hybrid materials are constructed by direct or synergistic templating. This principle will be illustrated using several examples of our most recent work including the synthesis and assembly of mesostructured silica in lipid helicoids and tobacco mosaic virus liquid crystals, DNA-driven self assembly of gold nanorods, and the synthesis of linear chains of nanoparticles and nanofilament arrays in water-in-oil microemulsions.

Supramolecular templating of organized inorganic matter Organized-matter chemistry is concerned with the synthesis, characterization and application of complex materials that exhibit order on length scales from the molecular to macroscopic. This talk will present an overview of several recent strategies in which the synthesis of organized inorganic nanostructures is controlled by organic supramolecular structures. A key aspect of this approach is the integration of organic self-organization and inorganic assembly such that hybrid materials are constructed by direct or synergistic templating. This principle will be illustrated using several examples of our most recent work including the synthesis and assembly of mesostructured silica in lipid helicoids and tobacco mosaic virus liquid crystals, DNA-driven self assembly of gold nanorods, and the surfactant-mediated synthesis of linear chains of nanoparticles and nanofilament arrays in water-in-oil microemulsions.


Synthesis and Design of Biomimetic Inorganic Materials and Nanostructures.

The study of biominerals, such as bones, shells and teeth, is providing new ideas and inspirations for materials chemistry. This lecture describes recent approaches to the “morphosynthesis” of inorganic materials, colloids and nanostructures with complex form and functionalized architecture. A key aspect of this approach is the integration of organic self-organization and inorganic assembly such that hybrid materials are constructed by template-directed processes. This principle will be illustrated using several examples of our recent work, including the synthesis and assembly of mesostructured silica in lipid helicoids, metallic nanowires in tobacco mosaic virus particles, formation of microporous calcium carbonate colloids in foams and emulsion droplets, and the synthesis of linear chains of nanoparticles and complex nanofilament arrays in water-in-oil microemulsions.


Nanotechnology in the test-tube

The assembly and organization of small-scale structures is a key challenge in nanotechnology. Current approaches tend to be based on sophisticated physical methods, such as the high resolution patterning of surfaces for controlled deposition of metallic nanoparticles and thin films. In contrast, chemical methods for the spontaneous formation of nanostructures with higher-order architectures have only recently been investigated. This short talk presents some new ideas and experiments concerned with the direct coupling of chemical synthesis and self-assembly to produce organized arrays of inorganic nano-crystals and nano-wires. The reactions take place in nano-sized water droplets that are surrounded by a shell of surfactant molecules and dispersed in oil as a stable emulsion. Aqueous salts, such as barium chloride and sodium sulfate, are encapsulated separately within the droplets, which are then mixed together to induce barium sulfate nucleation within the confined reaction space. By changing the chemical conditions, the system can be directed along various reaction pathways due to modifications in the strength of interactions between the surfactant molecules and the growing crystal surface. Weak interactions result in discrete nanoparticles, whereas intermediate binding gives rise to the spontaneous assembly of linear chains of regularly stacked nano-crystals interspaced with surfactant molecules. In contrast, very strong interactions inhibit crystallization such that amorphous barium sulfate nanoparticles are nucleated within the water droplets. These particles are unstable and slowly transform into crystalline barium sulfate within a few hours. Remarkably, this process produces unusual life-like microstructures, such as coiled nanofilament bundles, twisted helicoids and hierarchically stacked cones, due to competing forces arising from the reorganization of surface-bound surfactant molecules in association with inorganic crystallization. Our results indicate that the emergence of complexity and long-range organization in nanostructures can be achieved by time- and scale-dependent coupling of interactive components, and suggests that chemical routes will play an important role in the development of new materials and devices in nanotechnology.


Sol-gel Synthesis of Organized Matter.

The study of biological silicification in unicellular organisms such as diatoms and radiolaria, is providing new ideas and inspirations for the synthesis of organized inorganic matter. This lecture describes recent approaches to the “synthesis-with-construction” of silica-based materials with structural and morphological organization across a range of length scales. Several themes are addressed. These include the template-directed synthesis of covalently linked organosilicate hybrid clays with lamellar structure, and of ordered mesoporous MCM-41-type hybrid materials. The former are produced by reaction of organosiloxanes in the presence of inorganic templates (mono-octahedral Mg/OH/O brucite layers), whereas the latter are synthesized by co-condensation of siloxanes and organo-siloxanes in the presence of cylindrical micellar templates consisting of long chain surfactant molecules. In addition, the use of larger templates, such as ordered arrays of bacterial cellular filaments, in the formation of ordered macrostructures of amorphous silica or mesoporous silica, is described. Finally, a new method for synthesizing silica with microskeletal architecture is discussed. The approach employs condensation reactions in compartmentalized liquids as a means of generating organized patterns of inorganic matter.


Biomimetic Synthesis of Complex Inorganic Materials.

The study of biominerals, such as bones, shells and teeth, is providing new ideas and inspirations for materials chemistry. This lecture describes recent approaches to the “synthesis-with-construction” of inorganic materials with complex form and organized architecture. The key concepts to be discussed include, self-assembly and preorganization, molecular and spatial templating, length scale patterning, and morphosynthesis using organized reaction media. These will be illustrated by reference to recent work on;

  • the use of the iron storage protein, ferritin, to prepare dispersed nanocolloids with magnetic and semiconducting properties,
  • the self- and coassembly of surfactant micelles with cylindrical microstructures for the template-directed synthesis and patterning of iron oxides, gold nanoparticles and mesoporous silica,
  • the fabrication of bacterial superstructures to pattern CdS nanocrystalline superlattices and ordered macroporous silicas
  • the exploitation of compartmentalized liquids, such as reverse micelles and microemulsions for the synthesis of complex micro-skeletal forms of materials such as calcium carbonate, calcium phosphate and transition metal oxides

 


The Chemistry of Form

The emergence of complex form in living and non-living systems remains a deep question for scientists attempting to understand the origins and development of shape and structure. In recent years, biologists and physicists, respectively, have made significant advances in explaining fundamental problems in fields such as morphogenesis and pattern formation. Chemists, on the other hand, are only just beginning to contemplate the possibility of preparing man-made materials with life-like form. This review traces a route to the direct synthesis of inorganic structures with biomimetic form, beginning from an understanding of crystal morphology and biomineralization. The equilibrium form of crystals can be modified by surface-active additives but only within limits dictated by the symmetry of the unit cell. In contrast, biological minerals, such as shells, bones and teeth, are distinguished by a complexity of form that bears little resemblance to the underlying order of their inorganic crystals. By understanding the constructional processes that give rise to the inorganic structures of life it should be possible to develop a chemistry of form in the laboratory. For example, complex small-scale inorganic architectures are produced at room temperature by undertaking precipitation reactions in self-assembled organic media, such as surfactant micelles, block copolymer aggregates and microemulsion droplets. Unusual inorganic forms emerge when these reaction fields are subjected to instability thresholds and synthesis and self-assembly can be coupled to produce materials with higher-order organization. Like their biological counterparts, these hard inorganic structures represent new forms of organized matter which originate from soft chemistry.


Biomimetic Materials Chemistry: From Magnetic Proteins to Skeletons in the Beaker.

The study of biominerals, such as bones, shells and teeth, is providing new ideas and inspirations for materials and colloidal chemistry. This lecture describes recent approaches to the “synthesis-with-construction” of inorganic materials with organized architectures. Several themes are addressed. Firstly, the use of the iron storage protein, ferritin, to prepare dispersed nanocolloids with magnetic and semiconducting properties is described. Secondly, surfactant micelles with cylindrical microstructures have been utilised in the template-directed synthesis and patterning of iron oxides, gold nanoparticles and mesoporous silica. Ordered macroporous silicas can be prepared by using bacterial superstructures to template longer length scales in inorganic deposition. Finally, bicontinuous microemulsions have been exploited in the “inorganic morphosynthesis” of complex micro-skeletal forms of either calcium carbonate or calcium phosphate. These materials, which resemble biomineral architectures, originate from self-organized transitory reaction environments that are replicated in the inorganic materials by rapid crystallization processes.


Learning about Surface Design from Biomimetics.

A central idea in biomineralization is that the nucleation, growth and patterning of inorganic structures are controlled by interfacial interactions between mineral and protein/lipid surfaces. The study of inorganic-organic interfaces is therefore an important aspect of biomimetic materials chemistry which seeks to develop new synthetic routes to functional materials that are organized on various length scales from the nano- to macroscopic. This lecture illustrates the potential importance of electrostatic, stereochemical and geometric complementarity in oriented crystal nucleation under compressed Langmuir monolayers, and how some of these interactions can be used in the direct or synergistic templating of complex three-dimensional structures such as helical silica-lipid composites and silica-surfactant mesophases. New approaches, involving (i) biomolecular (antigen) coupling of gold nanoparticles via surface-adsorbed antibodies, (ii) synthesis and self-assembly of nanoparticle superstructures via hydrophobic-driven surface interactions in complex fluids, and (iii) emergent self-organization of calcium phosphate-block co-polymer nested colloids, are also described.


Inorganic Morphosynthesis in Self-organized Reaction Environments.

Organized-matter chemistry is concerned with the synthesis, characterization and application of complex materials that exhibit order on length scales from the molecular to macroscopic. Recently, biomimetic strategies have been developed for the synthesis of organized inorganic-based structures. A key aspect of this approach is the integration of organic self-assembly and inorganic reaction chemistry such that hybrid materials are constructed either by direct or synergistic templating. This lecture illustrates how organic mesophases and complex fluids – for example, lyotropic liquid crystals, lipid helices, viroid tubes, polymer micelles, microemulsions, foams – can be used for the one-step synthesis of inorganic (silica, iron oxide, BaSO4, Ca phosphate, CaCO3 etc.) architectures with unusual morphological form (morphosynthesis). In particular, the lecture focuses on the emergence of organized colloidal superstructures, such as nested calcium phosphate-block copolymer micelles (collaborative work with Prof. M. Antonietti, Berlin) and linear chains of barium chromate nanoparticles assembled from AOT microemulsions. A mechanism in which confinement of the incipient inorganic phase transforms the metastable micellar structures into adaptive inorganic-organic structures is discussed.


Nanotectonics: Coupled Synthesis and Self-assembly of Nanoparticle-based Higher-order Structures.

Recently, new strategies have been developed for the synthesis of organized inorganic nanostructures using nanoparticle-based building blocks (nanotectonics). A key aspect of this approach is the integration of organic self-organization and nanoparticle assembly such that hybrid materials are constructed by direct or synergistic templating. This principle will be illustrated using several examples of our recent work including the control of nanoparticle assembly by biological superstructures, such as supercellular bacterial threads and 2-D porous protein crystals, and via interparticle conjugation using biomolecular-based surface recognition. The lecture will also focus on the coupled synthesis and self-assembly of higher-order nanoparticle-based structures, such as linear chains and nanofilament arrays of BaSO4 and BaCrO4 crystallites, in complex fluids (microemulsions).


Holey Silica! – from Interior Design to Nanotectonics.

Organized-matter chemistry is concerned with the synthesis, characterization and application of complex materials that exhibit structural and compositional order on length scales from the molecular to macroscopic. Porous materials such as mesoscopically ordered silicas, represent an important class of organized matter that originates from synthetic strategies involving template-directed self-assembly. In general, this strategy is based on structural and morphological replication of organic architectures and although usually limited to the mesoscopic scale, in principle there is no reason why the method should not be extended to longer length scales and to systems involving multiplex templating. To illustrate this, examples of porous silicas prepared using liquid crystals of tobacco mosaic virus (TMV), sponge-like organic matrices of biomineralized cuttlebone, organic crystal fibres, and threads of bacterial superstructures fibres will be briefly presented in the lecture. A complementary approach to porous architectures involves the use of nanoparticle-based building blocks (nanotectonics), which are positioned and assembled within the void spaces of ordered organic templates. Clearly, if the nanoparticles have structured porous interiors then these can be incorporated into the walls of the higher-order assembly to produce hierarchical materials. For this reason, we have recently synthesized nanoparticles with various types of porous interiors zeolite (silicalite), MCM-41, and a new structure consisting of radially arranged linear channels and used these building blocks in association with various templates, such as bacterial superstructures, latex beads, and sponge-like polymer gels. Aspects of this work will be reviewed in the lecture.

Material Futures: Towards Synthetic Cellularity via Protocell Design and Construction 

The design and construction of compartmentalized materials ensembles for modelling complex biological systems, exploring the origin of life, and advancing future living technologies is attracting considerable interest in a wide range of research communities. In this talk, I will review some recent experiments undertaken in my laboratory that provide steps towards synthetic cellularity using bioinspired materials chemistry principles and techniques. I will discuss four new protocell models based on; (i) nanoparticle self-assembly (colloidosomes) [1], (ii) interfacial assembly of protein-polymer nanoconjugates (proteinosomes) [2], (iii) micro-droplet formation (coacervation) [3,4], and hybrids of the above [5]. I will use these new model systems to discuss pathways towards chemical cognition, modulated reactivity, basic signalling pathways and non-equilibrium activation in compartmentalized artificial micro-ensembles.

References:

[1]. Li M et al., Membrane-gated permeability in self-activated inorganic protocells. Nature Chem., 5, 529-536 (2013).[2]. Huang X, et al., Interfacial assembly of protein-polymer nano-conjugates into stimulus-responsive biomimetic protocells. Nature Commun. 4, 2239 (2013) DOI: 10.1038/ncomms 3239, 1-9 (2013).[3]. Koga, S., et al., Peptide–nucleotide microdroplets as a step towards a membrane-free protocell model. Nature Chem. 3, 720-724 (2011).[4] Yin Y, et al., Non-equilibrium behaviour in coacervate-based protocells under electric field-induced excitation. Nature Commun. 7, 10658, 1-7 (2016); DOI:10.1038/ncomms10658 1-7 (2016).[5] Tang T-Y D, et al., Fatty acid membrane assembly on coacervate micro-droplets as a step towards a hybrid protocell model. Nature Chem. 6, 527- 533 (2014).

ETH, Zurich (2016)