Nano-enabled synthetic biology: A cell mimic based sensing platform for exploiting biochemical networks

Exploring and understanding how the smallest scale features of a cell affect biochemical reactions has always been a challenge. Nanoscale fabrication advancements have allowed scientists to create small volume reaction containers that resemble the physical scale of cell membranes. Engineers seek to use biological design principles to manipulate information and import new functionality to such synthetic devices, which in turn, play a crucial role in allowing them to explore the effects of physical transport and extreme conditions of temperature and pH on reaction systems. Engineered reaction containers can be physically and chemically defined to control the flux of molecules of different sizes and charge. The design and testing of such a container is described here. It has a volume of 19 pL and has defined slits of 10-200 nm. The device successfully contains DNA and protein molecules and has been used to conduct and analyze enzyme reactions under different substrate concentrations and a continuous cell-free protein synthesis. The effect of DNA concentration and slit size on protein yield is also discussed. Glucose oxidase and horseradish peroxidase were loaded in the small volume container and fed with a solution containing glucose and Amplex Red™ to produce Resorufin. Fluorescent microscopy was used to monitor the reaction, which was carried out under microfluidic control. Enzyme kinetics were characterized and compared with conventional scale results. Continuous cell free protein synthesis in arrays of nanoporous, picoliter volume containers has also been achieved. A multiscale fabrication process allows for the monolithic integration of the containers and an addressable microfluidic network. Synthesis of enhanced green fluorescent protein (eGFP) in the nanoporous containers continues beyond 24 hours and yields more than twice the amount of protein, on a per volume basis, than conventional scale batch reactions. These picoliter, nanoporous containers provide new ways for quick determination of enzyme kinetics and continuous protein synthesis in microfluidic systems. They can be used in a wide variety of applications such as drug discovery, clinical diagnostics and high-throughput screening

Encryption and steganography of synthetic gene circuits

Artificial gene circuits represent intellectual property that under some circumstances may need to be obfuscated to prevent discovery by third parties. Here the authors use encryption by overlapping recombinase sites and steganography by the introduction of superfluous components, to obscure circuit topology

Enzyme reactions in nanoporous, picoliter volume containers

Advancements in nanoscale fabrication allow creation of small-volume reaction containers that can facilitate the screening and characterization of enzymes. A porous, ∼19 pL volume vessel has been used in this work to carry out enzyme reactions under varying substrate concentrations. Assessment of small-molecule and green fluorescent protein diffusion from the vessels indicates that pore sizes on the order of 10 nm can be obtained, allowing capture of proteins and diffusive exchange of small molecules. Glucose oxidase and horseradish peroxidase can be contained in these structures and diffusively fed with a solution containing glucose and the fluorogenic substrate amplex red through the engineered nanoscale pore structure. Fluorescent microscopy was used to monitor the reaction, which was carried out under microfluidic control. Kinetic characteristics of the enzyme (K m and V max) were evaluated and compared with results from conventional scale reactions. These picoliter, nanoporous containers can facilitate quick determination of enzyme kinetics in microfluidic systems without the requirement of surface tethering and can be used for applications in drug discovery, clinical diagnostics, and high-throughput screening

Oligomeric remodelling by molecular glues revealed using native mass spectrometry and mass photometry

Molecular glues stabilize interactions between E3 ligases and novel substrates to promote substrate degradation, thereby facilitating the inhibition of traditionally undruggable protein targets. However, most known molecular glues have been discovered fortuitously or are based on well-established chemical scaffolds. Efficient approaches for discovering and characterising the effects of molecular glues on protein interactions are required to accelerate the discovery of novel agents. Here, we demonstrate that native mass spectrometry and mass photometry can provide unique insights into the physical mechanism of molecular glues, revealing previously unknown effects of such small molecules on the oligomeric organization of E3 ligases. When compared to well-established solution phase assays, native mass spectrometry provides accurate quantitative descriptions of molecular glue potency and efficacy while also enabling the binding specificity of E3 ligases to be determined in a single, rapid measurement. Such mechanistic insights should accelerate the rational development of molecular glues to afford powerful therapeutic agents

Cell free translation in engineered picoliter volume containers

Engineers seek to use biological design principles to manipulate information and import new functionality to synthetic devices. Such devices inspired by natural systems could, in turn, play a crucial role in allowing biologists to explore the effects of physical transport and extreme conditions of temperature and pH on reaction systems. For example, engineered reaction containers can be physically and chemically defined to control the flux of molecules of different sizes and charge. The design and testing of such a container is described here. It has a volume of 19pL with defined slits of 200nm. The device successfully contained DNA and protein molecules and is evaluated for carrying out cell-free protein synthesis. The effect of DNA concentration and slit size on protein yield is discussed

Development and fabrication of nanoporous silicon-based bioreactors within a microfluidic chip

Multi-scale lithography and cryogenic deep reactive ion etching techniques were used to create ensembles of nanoporous, picolitre volume, reaction vessels within a microfluidic system. The fabrication of these vessels is described and how this process can be used to tailor vessel porosity by controlling the width of slits that constitute the vessel pores is demonstrated. Control of pore size allows the containment of nucleic acids and enzymes that are the foundation of biochemical reaction systems, while allowing smaller reaction constituents to traverse the container membrane and continuously supply the reaction. In this work, a 5.4 kb DNA plasmid was retained within the reaction vessels and labeled under microfluidic control with ethidium bromide as an initial proof-of-principle. Subsequently, a coupled enzyme reaction, in which glucose oxidase (GOX) and horseradish peroxidase (HRP) were contained and fed with a substrate solution of glucose and Amplex Red™ to produce fluorescent resorufin, was carried out under microfluidic control and monitored using fluorescent microscopy. The fabrication techniques presented are broadly applicable and can be adapted to produce devices in which a variety of high aspect ratio, nanoporous silicon structures can be integrated within a microfluidic network. The devices shown here are amenable to being scaled in number and organized to implement more complex reaction systems for applications in sensing and actuation as well as fundamental studies of biological reaction systems

Biosynthetic production and evaluation of knotted peptide topology and characteristics.

Knotted peptides present a wealth of structurally diverse, biologically-active molecules, with the inhibi-tor cystine knot or knottin folds among the most prevalent. Many of these natural products interact with extracellular targets such as voltage-gated ion channels with exquisite selectivity and potency, making them intriguing therapeutic modalities. However, such compounds are often produced by exotic organisms in low concentrations, making structure determination and biological characterization challenging. Heterologous expression in bacterial hosts could potential-ly solve these issues by making scalable production of these compounds accessible - though this methodology would rely on correct in vivo disulfide formation and folding in the absence of native oxidative folding pathways that are pre-sent in the original organisms. We screened expression constructs for a heterologously biosynthesized knotted peptide to determine the most influential parameters for successful disulfide folding using NMR spectroscopic fingerprinting to validate the topological structure of folded products. To better understand this emerging modality of peptides, we performed pharmacokinetic characterization which indicate the interlocking disulfide structure minimizes liabilities of linear peptide sequences and has a profound influence on these molecules’ behavior in vivo. We then developed an assay to study the solution folding of toxin residues in real time, providing a method for studying the complex folding process these molecules undergo during maturation

Surface charge-and space-dependent transport of proteins in crowded environments of nanotailored posts

The reaction and diffusion of molecules across barriers and through crowded environments is integral to biological system function and to separation technologies. Ordered, microfabricated post arrays are a promising route to creating synthetic barriers with controlled chemical and physical characteristics. They can be used to create crowded environments, to mimic aspects of cellular membranes, and to serve as engineered replacements of polymer-based separation media. Here, the translational diffusion of fluorescein isothiocyante and various forms of green fluorescent protein (GFP), including supercharged variants, are examined in a siliconbased post array environment. The technique of fluorescence recovery after photobleaching (FRAP) is combined with analytical approximations and numerical simulations to assess the relative effects of reaction and diffusion on molecular transport, respectively. FRAP experiments were conducted for 64 different cases where the molecular species, the density of the posts, and the chemical surface charge of the posts were varied. In all cases, the dense packing of the posts hindered the diffusive transport of the fluorescent species. The supercharged GFPs strongly interacted with oppositely charged surfaces. With similar molecular and surface charges, transport is primarily limited by hindered diffusion. For conventional, enhanced GFP in a positively charged surface environment, transport was limited by the coupled action of hindered diffusion and surface interaction with the posts. Quantification of the size-, space-, time-, and charge-dependent translational diffusion in the post array environments can provide insight into natural processes and guide the design and development of selective membrane systems

Understanding Flavin-Dependent Halogenase Reactivity via Substrate Activity Profiling

The activity of four native FDHs and four engineered FDH variants on 93 low-molecular-weight arenes was used to generate FDH substrate activity profiles. These profiles provided insights into how substrate class, functional group substitution, electronic activation, and binding affect FDH activity and selectivity. The enzymes studied could halogenate a far greater range of substrates than have been previously recognized, but significant differences in their substrate specificity and selectivity were observed. Trends between the electronic activation of each site on a substrate and halogenation conversion at that site were established, and these data, combined with docking simulations, suggest that substrate binding can override electronic activation even on compounds differing appreciably from native substrates. These findings provide a useful framework for understanding and exploiting FDH reactivity for organic synthesis