Molecular Dynamics Simulations Reveal a Dielectric-Responsive Coronal Structure in Protein–Polymer Surfactant Hybrid Nanoconstructs

Partitioning of an Enzyme-Polymer Surfactant Nanocomplex into Lipid-Rich Cellular Compartments Drives In Situ Hydrolysis of Organophosphates

Most organophosphates (OPs) are hydrophobic, and after exposure, can sequester into lipophilic regions within the body, such as adipose tissue, resulting in long term chronic effects. Consequently, there is an urgent need for therapeutic agents that can decontaminate OPs in these hydrophobic regions. Accordingly, an enzyme-polymer surfactant nanocomplex is designed and tested comprising chemically supercharged phosphotriesterase (Agrobacterium radiobacter; arPTE) electrostatically conjugated to amphiphilic polymer surfactant chains ([cat.arPTE][S-]). Experimentally-derived structural data are combined with molecular dynamics (MD) simulations to provide atomic level detail on conformational ensembles of the nanocomplex using dielectric constants relevant to aqueous and lipidic microenvironments. These show the formation of a compact admicelle pseudophase surfactant corona under aqueous conditions, which reconfigures to yield an extended conformation at a low dielectric constant, providing insight into the mechanism underpinning cell membrane binding. Significantly, it demonstrated that [cat.arPTE][S-] spontaneously binds to human mesenchymal stem cell membranes (hMSCs), resulting in on-cell OP hydrolysis. Moreover, the nanoconstruct can endocytose and partition into the intracellular fatty vacuoles of adipocytes and hydrolyze sequestered OP.

Ionic Liquid Gating Induces Anomalous Permeation through Membrane Channel Proteins

Membrane channel proteins (MCPs) play key roles in matter transport through cell membranes and act as major targets for vaccines and drugs. For emerging ionic liquid (IL) drugs, a rational understanding of how ILs affect the structure and transport function of MCP is crucial to their design. In this work, GPU-accelerated microsecond-long molecular dynamics simulations were employed to investigate the modulating mechanism of ILs on MCP. Interestingly, ILs prefer to insert into the lipid bilayer and channel of aquaporin-2 (AQP2) but adsorb on the entrance of voltage-gated sodium channels (Nav). Molecular trajectory and free energy analysis reflect that ILs have a minimal impact on the structure of MCPs but significantly influence MCP functions. It demonstrates that ILs can decrease the overall energy barrier for water through AQP2 by 1.88 kcal/mol, whereas that for Na+ through Nav is increased by 1.70 kcal/mol. Consequently, the permeation rates of water and Na+ can be enhanced and reduced by at least 1 order of magnitude, respectively. Furthermore, an abnormal IL gating mechanism was proposed by combining the hydrophobic nature of MCP and confined water/ion coordination effects. More importantly, we performed experiments to confirm the influence of ILs on AQP2 in human cells and found that treatment with ILs significantly accelerated the changes in cell volume in response to altered external osmotic pressure. Overall, these quantitative results will not only deepen the understanding of IL-cell interactions but may also shed light on the rational design of drugs and disease diagnosis.

Polymerized and Colloidal Ionic Liquids─Syntheses and Applications

The breadth and importance of polymerized ionic liquids (PILs) are steadily expanding, and this review updates advances and trends in syntheses, properties, and applications over the past five to six years. We begin with an historical overview of the genesis and growth of the PIL field as a subset of materials science. The genesis of ionic liquids (ILs) over nano to meso length-scales exhibiting 0D, 1D, 2D, and 3D topologies defines colloidal ionic liquids, CILs, which compose a subclass of PILs and provide a synthetic bridge between IL monomers (ILMs) and micro to macro-scale PIL materials. The second focus of this review addresses design and syntheses of ILMs and their polymerization reactions to yield PILs and PIL-based materials. A burgeoning diversity of ILMs reflects increasing use of nonimidazolium nuclei and an expanding use of step-growth chemistries in synthesizing PIL materials. Radical chain polymerization remains a primary method of making PILs and reflects an increasing use of controlled polymerization methods. Step-growth chemistries used in creating some CILs utilize extensive cross-linking. This cross-linking is enabled by incorporating reactive functionalities in CILs and PILs, and some of these CILs and PILs may be viewed as exotic cross-linking agents. The third part of this update focuses upon some advances in key properties, including molecular weight, thermal properties, rheology, ion transport, self-healing, and stimuli-responsiveness. Glass transitions, critical solution temperatures, and liquidity are key thermal properties that tie to PIL rheology and viscoelasticity. These properties in turn modulate mechanical properties and ion transport, which are foundational in increasing applications of PILs. Cross-linking in gelation and ionogels and reversible step-growth chemistries are essential for self-healing PILs. Stimuli-responsiveness distinguishes PILs from many other classes of polymers, and it emphasizes the importance of segmentally controlling and tuning solvation in CILs and PILs. The fourth part of this review addresses development of applications, and the diverse scope of such applications supports the increasing importance of PILs in materials science. Adhesion applications are supported by ionogel properties, especially cross-linking and solvation tunable interactions with adjacent phases. Antimicrobial and antifouling applications are consequences of the cationic nature of PILs. Similarly, emulsion and dispersion applications rely on tunable solvation of functional groups and on how such groups interact with continuous phases and substrates. Catalysis is another significant application, and this is an historical tie between ILs and PILs. This component also provides a connection to diverse and porous carbon phases templated by PILs that are catalysts or serve as supports for catalysts. Devices, including sensors and actuators, also rely on solvation tuning and stimuli-responsiveness that include photo and electrochemical stimuli. We conclude our view of applications with 3D printing. The largest components of these applications are energy related and include developments for supercapacitors, batteries, fuel cells, and solar cells. We conclude with our vision of how PIL development will evolve over the next decade.

Molecular simulations explain the exceptional thermal stability, solvent tolerance and solubility of protein-polymer surfactant bioconjugates in ionic liquids

Proteins complexed electrostatically with polymer surfactants constitute a viscous liquid by themselves, called the solvent-free protein liquid (SFPL). A solution of SFPL in a room temperature ionic liquid (PS-IL) offers the protein hyperthermal stability, higher solubility and greater IL tolerance. A generic understanding of these protein-polymer systems is obtained herein through extensive atomistic molecular dynamics simulations of three different enzymes (lipase A, lysozyme and myoglobin) under various conditions. Along with increased intra-protein hydrogen bonding, the surfactant coating around the proteins imparts greater thermal stability, and also aids in screening protein-IL interactions, endowing them IL tolerance. The reduced surface polarity of the protein-polymer bioconjugate and hydrogen bonding between the ethylene glycol groups of the surfactant and the IL cation contribute to the facile solvation of the protein in its PS-IL form. The results presented here rationalize several experimental observations and will aid in the improved design of such hybrid materials for sustainable catalysis.

Insights into substrate behavior in a solvent-free protein liquid to rationalize its reduced catalytic rate

When proteins are engineered with a polymer surfactant coating on their surface, they can form a liquid phase by themselves, without the need for a solvent, such as, say, water. However, such solvent-free protein liquids (SFPL), despite their capability to function at temperatures above those in aqueous solutions, exhibit much reduced catalytic rates. A comprehensive understanding of the nature of substrates in such liquids is crucial to reason out the reduced catalytic activity of enzymes as SFPL media, and thus identify the means to improve the same. Employing atomistic molecular dynamics simulations of lipase A from Bacillus subtilis in its SFPL form, we demonstrate that at low concentrations, the substrate molecules are located mostly in the hydrophilic layer of the surfactant shell that ensheaths the enzyme; substrates in this SFPL are present in various conformations with similar propensities as in the aqueous solution. Slower translational diffusion and reorientational dynamics, as well as the reduced tendency of a substrate molecule to closely interact with the enzymes in the SFPL medium have been identified herein as the contributing factors for the reduced activity of enzymes in this hybrid liquid. At high concentrations of substrates corresponding to those used in in vitro experiments, the formation of an enzyme-substrate complex is observed. Microscopic insights reported here can aid in the choice of surfactants to improve the catalytic rate of enzymes in SFPL.

Potentialities of graphene and its allied derivatives to combat against SARS-CoV-2 infection

Graphene is a two-dimensional material with sp2 hybridization that has found its broad-spectrum potentialities in various domains like electronics, robotics, aeronautics, etc.; it has recently gained its utilities in the biomedical domain. The unique properties of graphene and its derivatives of graphene have helped them find their utilities in the biomedical domain. Additionally, the sudden outbreak of SARS-CoV-2 has immensely expanded the research field, which has also benefitted graphene and its derivatives. Currently, the world is facing a global pandemic due to the sudden outbreak of Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2), also known as COVID-19, from its major onset in Wuhan city, China, in December 2019. Presently, many new variants and mutants appear, which is more harmful than previous strains. However, researchers and scientists are focused on understanding the target structure of coronavirus, mechanism, causes and transmission mode, treatment, and alternatives to cure these diseases in this critical pandemic situation; many findings are achieved, but much more is unknown and pending to be explored. This review paper is dedicated to exploring the utilities of graphene and its derivatives in combating the SARS-CoV-2 by highlighting their mechanism and applications in the fabrication of biosensors, personal protection equipment (PPE) kits, 3-D printing, and antiviral coatings. Further, the paper also covers the cytotoxicity caused by graphene and its derivatives and highlights the graphene-based derivatives market aspects in biomedical domains. Thus, graphene and graphene-derived materials are our new hope in this pandemic time, and this review helps acquire broad knowledge about them.

Three-Dimensional Printable Enzymatically Active Plastics

Here, we describe a facile route to the synthesis of enzymatically active highly fabricable plastics, where the enzyme is an intrinsic component of the material. This is facilitated by the formation of an electrostatically stabilized enzyme-polymer surfactant nanoconstruct, which, after lyophilization and melting, affords stable macromolecular dispersions in a wide range of organic solvents. A selection of plastics can then be co-dissolved in the dispersions, which provides a route to bespoke 3D enzyme plastic nanocomposite structures using a wide range of fabrication techniques, including melt electrowriting, casting, and piston-driven 3D printing. The resulting constructs comprising active phosphotriesterase (arPTE) readily detoxify organophosphates with persistent activity over repeated cycles and for long time periods. Moreover, we show that the protein guest molecules, such as arPTE or sfGFP, increase the compressive Young's modulus of the plastics and that the identity of the biomolecule influences the nanomorphology and mechanical properties of the resulting materials. Overall, we demonstrate that these biologically active nanocomposite plastics are compatible with state-of-the-art 3D fabrication techniques and that the methodology could be readily applied to produce robust and on-demand smart nanomaterial structures.

An artificial membrane binding protein-polymer surfactant nanocomplex facilitates stem cell adhesion to the cartilage extracellular matrix

One of the major challenges within the emerging field of injectable stem cell therapies for articular cartilage (AC) repair is the retention of sufficient viable cell numbers at the site of injury. Even when delivered via intra-articular injection, the number of stem cells retained at the target is often low and declines rapidly over time. To address this challenge, an artificial plasma membrane binding nanocomplex was rationally designed to provide human mesenchymal stem cells (hMSCs) with increased adhesion to articular cartilage tissue. The nanocomplex comprises the extracellular matrix (ECM) binding peptide of a placenta growth factor-2 (PlGF-2) fused to a supercharged green fluorescent protein (scGFP), which was electrostatically conjugated to anionic polymer surfactant chains to yield [S^-]scGFP_PlGF2. The [S^-]scGFP_PlGF2 nanocomplex spontaneously inserts into the plasma membrane of hMSCs, is not cytotoxic, and does not inhibit differentiation. The nanocomplex-modified hMSCs showed a significant increase in affinity for immobilised collagen II, a key ECM protein of cartilage, in both static and dynamic cell adhesion assays. Moreover, the cells adhered strongly to bovine ex vivo articular cartilage explants resulting in high cell numbers. These findings suggest that the re-engineering of hMSC membranes with [S^-]scGFP_PlGF2 could improve the efficacy of injectable stem cell-based therapies for the treatment of damaged articular cartilage.

Modeling the Mechanical Response of Microtubule Lattices to Pressure

Microtubules, the largest and stiffest filaments of the cytoskeleton, have to be well adapted to the high levels of crowdedness in cells to perform their multitude of functions. Furthermore, fundamental processes that involve microtubules, such as the maintenance of the cellular shape and cellular motion, are known to be highly dependent on external pressure. In light of the importance of pressure for the functioning of microtubules, numerous studies interrogated the response of these cytoskeletal filaments to osmotic pressure, resulting from crowding by osmolytes, such as poly(ethylene glycol)/poly(ethylene oxide) (PEG/PEO) molecules, or to direct applied pressure. The interpretation of experiments is usually based on the assumptions that PEG molecules have unfavorable interactions with the microtubule lattices and that the behavior of microtubules under pressure can be described by using continuous models. We probed directly these two assumptions. First, we characterized the interaction between the main interfaces in a microtubule filament and PEG molecules of various sizes using a combination of docking and molecular dynamics simulations. Second, we studied the response of a microtubule filament to compression using a coarse-grained model that allows for the breaking of lattice interfaces. Our results show that medium length PEG molecules do not alter the energetics of the lateral interfaces in microtubules but rather target and can penetrate into the voids between tubulin monomers at these interfaces, which can lead to a rapid loss of lateral interfaces under pressure. Compression of a microtubule under conditions corresponding to high osmotic pressure results in the formation of the deformed phase found in experiments. Our simulations show that the breaking of lateral interfaces, rather than the buckling of the filament inferred from the continuous models, accounts for the deformation.

An atomistic view of solvent-free protein liquids: the case of Lipase A

Solvent-free enzymes hold the promise of being able to deliver higher activity at elevated temperatures by virtue of them being not limited by the boiling point of the solvent. They have been realized in the liquid phase through a polymer surfactant coating on the protein surface. However, a clear understanding of intermolecular interactions, structure, dynamics, and the behaviour of the minuscule amount of water present in the solvent-free protein liquid is essential to enhance the activity of these biofluids. Using atomistic molecular dynamics simulations, we demonstrate that the scaled spatial correlations between proteins in the hybrid liquid phase of Lipase A enzymes are comparable to the inter-particle correlations in a noble gas fluid. The hydrophilic region of the surfactants forms a coronal layer around each enzyme which percolates throughout the liquid, while the hydrophobic parts are present as disjointed clusters. Inter-surfactant interactions, determined to be attractive and in the range of -200 to -300 kcal mol^-1, stabilize the liquid state. While the protein retains its native state conformational dynamics in the solvent-free form, the fluxionality of its side chains is much reduced; at 333 K, the latter is found to be equivalent to that of the enzyme in an aqueous solution at 249 K. Despite the sluggishness of the solvent-free enzyme, some water molecules exhibit high mobility and transit between enzymes primarily via the interspersed hydrophilic regions. These microscopic insights offer ideas to improve substrate diffusion in the liquid to enable the enhancement of catalytic activity.

Diffusivelike Motions in a Solvent-Free Protein-Polymer Hybrid

The interaction between proteins and hydration water stabilizes protein structure and promotes functional dynamics, with water translational motions enabling protein flexibility. Engineered solvent-free protein-polymer hybrids have been shown to preserve protein structure, function, and dynamics. Here, we used neutron scattering, protein and polymer perdeuteration, and molecular dynamics simulations to explore how a polymer dynamically replaces water. Even though relaxation rates and vibrational properties are strongly modified in polymer coated compared to hydrated proteins, liquidlike polymer dynamics appear to plasticize the conjugated protein in a qualitatively similar way as do hydration-water translational motions.

Preparation and application of solvent-free liquid proteins with enhanced thermal and anhydrous stabilities

This perspective details a robust chemical modification strategy to protect proteins from temperature, aggregation, and non-aqueous environments.

The Effect of Residual Triton X-100 on Structural Stability and Infection Activity of Adenovirus Particles

To ensure the high purity and biological activity of the adenovirus vector to be used for clinical applications, a stable and linearly scalable preparation method is highly imperative. During the adenovirus-harvesting process, the Triton X-100-based lysis method possesses the advantages of higher efficiency as well as easier linearization and amplification. Most Triton X-100 can be removed from the adenovirus sample by chromatographic purification. However, there is no report that a small amount of residual Triton X-100, present in adenovirus sample, can affect the particle integrity, infectivity, and structure of adenoviruses. Here, we found that although residual Triton X-100 affected the short-term stability, purity, infectivity, and structure of adenoviruses at 37°C, it did not hamper these properties of adenoviruses at 4°C. This study suggests that although the Triton X-100-based lysis method is a simple, efficient, and easy-to-scale process for lysing host cells to release the adenovirus, the storage conditions of adenovirus products must be taken into consideration.

Solvent-free liquid avidin as a step toward cold chain elimination

The temperature sensitivity of vaccines and therapeutic proteins forces the distribution of life-saving treatments to rely heavily on the temperature-controlled (usually 2-8°C) supply and distribution network known as the cold chain. Here, using avidin as a model, we demonstrate how surface engineering could significantly increase the thermal stability of therapeutic proteins. A combination of spectroscopic (Fourier transform infrared, circular dichroism, and ultraviolet-visible) and scattering techniques (dynamic light scattering, small-angle, and wide-angle X-ray scattering) were deployed to probe the activity, structure, and stability of the model protein. Temperature-dependent synchrotron radiation circular dichroism spectroscopy was used to demonstrate a significant increase in thermal stability, with a half denaturation temperature of 139.0°C and reversible unfolding with modified avidin returning to a 90% folded state when heated to temperatures below 100°C. Accelerated aging studies revealed that modified avidin retained its secondary structure after storage at 40°C for 56 days, equivalent to 160 days at 25°C. Furthermore, binding studies with multiple ligands revealed that the binding site remained functional after modification. As a result, this approach has potential as a storage technology for therapeutic proteins and the elimination of the cold chain, enabling the dissemination of life-saving vaccines worldwide.

Tandem catalysis in multicomponent solvent-free biofluids

Enzymes are widely employed to reduce the environmental impact of chemical industries as biocatalysts improve productivity and offer high selectively under mild reaction conditions in a diverse range of chemical transformations. The poor stability of biomacromolecules under reaction conditions is often a critical bottleneck to their application. Protein engineering or immobilization onto solid substrates may remedy this limitation but, unfortunately, this is often at the expense of catalytic potency or substrate specificity. In this work, we show that the combinatorial approach of chemical modification and supramolecular nanoencapsulation can endow mechanistically diverse enzymes with apparent extremophilic behavior. A protein-polymer surfactant core-shell architecture facilitates construction of increasingly complex biofluids from individual biosynthetic components, each of which retain biological activity at hydration levels almost two orders of magnitude below solvation. The herein constructed multifunctional biofluids operate in tandem up to 150 °C and in the total absence of solvent under apparent diffusional mass-transport limitation. The biosynthetic promotion of extremophilic traits for enzymes with diverse catalytic motions and chemical functions highlights the extraordinary capacity for a viscous surfactant milieu to replace both hydration and bulk waters.

Sequential Electrostatic Assembly of a Polymer Surfactant Corona Increases Activity of the Phosphotriesterase arPTE

We present a new methodology for the generation of discrete molecularly dispersed enzyme-polymer-surfactant bioconjugates. Significantly, we demonstrate that >3-fold increase in the catalytic efficiency of the diffusion-limited phosphotriesterase arPTE can be achieved through sequential electrostatic addition of cationic and anionic polymer surfactants, respectively. Here, the polymer surfactants assemble on the surface of the enzyme via ion exchange to yield a compact corona. The observed rate enhancement is consistent with a mechanism whereby the polymer-surfactant corona gives rise to a decrease in the dielectric constant in the vicinity of the active site of the enzyme, accelerating the rate-determining product diffusion step. The facile methodology has significant potential for increasing the efficiency of enzymes and could therefore have a substantially positive impact for industrial enzymology.

Designer artificial membrane binding proteins to direct stem cells to the myocardium

We present a new cell membrane modification methodology where the inherent heart tissue homing properties of the infectious bacteria Streptococcus gordonii are transferred to human stem cells. This is achieved via the rational design of a chimeric protein-polymer surfactant cell membrane binding construct, comprising the cardiac fibronectin (Fn) binding domain of the bacterial adhesin protein CshA fused to a supercharged protein. Significantly, the protein-polymer surfactant hybrid spontaneously inserts into the plasma membrane of stem cells without cytotoxicity, instilling the cells with a high affinity for immobilized fibronectin. Moreover, we show that this cell membrane reengineering approach significantly improves retention and homing of stem cells delivered either intracardially or intravenously to the myocardium in a mouse model.

Accelerated Molecular Dynamics Simulation for Helical Proteins Folding in Explicit Water

In this study, we examined the folding processes of eight helical proteins (2I9M, TC5B, 1WN8, 1V4Z, 1HO2, 1HLL, 2KFE, and 1YYB) at room temperature using the explicit solvent model under the AMBER14SB force field with the accelerated molecular dynamics (AMD) and traditional molecular dynamics (MD), respectively. We analyzed and compared the simulation results obtained by these two methods based on several aspects, such as root mean square deviation (RMSD), native contacts, cluster analysis, folding snapshots, free energy landscape, and the evolution of the radius of gyration, which showed that these eight proteins were successfully and consistently folded into the corresponding native structures by AMD simulations carried out at room temperature. In addition, the folding occurred in the range of 40~180 ns after starting from the linear structures of the eight proteins at 300 K. By contrast, these stable folding structures were not found when the traditional molecular dynamics (MD) simulation was used. At the same time, the influence of high temperatures (350, 400, and 450 K) is also further investigated. Study found that the simulation efficiency of AMD is higher than that of MD simulations, regardless of the temperature. Of these temperatures, 300 K is the most suitable temperature for protein folding for all systems. To further investigate the efficiency of AMD, another trajectory was simulated for eight proteins with the same linear structure but different random seeds at 300 K. Both AMD trajectories reached the correct folded structures. Our result clearly shows that AMD simulation are a highly efficient and reliable method for the study of protein folding.

Artificial cell membrane binding thrombin constructs drive in situ fibrin hydrogel formation

Cell membrane re-engineering is emerging as a powerful tool for the development of next generation cell therapies, as it allows the user to augment therapeutic cells to provide additional functionalities, such as homing, adhesion or hypoxia resistance. To date, however, there are few examples where the plasma membrane is re-engineered to display active enzymes that promote extracellular matrix protein assembly. Here, we report on a self-contained matrix-forming system where the membrane of human mesenchymal stem cells is modified to display a novel thrombin construct, giving rise to spontaneous fibrin hydrogel nucleation and growth at near human plasma concentrations of fibrinogen. The cell membrane modification process is realised through the synthesis of a membrane-binding supercationic thrombin-polymer surfactant complex. Significantly, the resulting robust cellular fibrin hydrogel constructs can be differentiated down osteogenic and adipogenic lineages, giving rise to self-supporting monoliths that exhibit Young's moduli that reflect their respective extracellular matrix compositions.

Insight into the Structure and Activity of Surface-Engineered Lipase Biofluids

Despite a successful application of solvent-free liquid protein (biofluids) concept to a number of commercial enzymes, the technical advantages of enzyme biofluids as hyperthermal stable biocatalysts cannot be fully utilized as up to 90-99% of native activities are lost when enzymes were made into biofluids. With a two-step strategy (site-directed mutagenesis and synthesis of variant biofluids) on Bacillus subtilis lipase A (BsLA), we elucidated a strong dependency of structure and activity on the number and distribution of polymer surfactant binding sites on BsLA surface. Here, it is demonstrated that improved BsLA variants can be engineered via site-mutagenesis by a rational design, either with enhanced activity in aqueous solution in native form, or with improved physical property and increased activity in solvent-free system in the form of a protein liquid. This work answered some fundamental questions about the surface characteristics for construction of biofluids, useful for identifying new strategies for developing advantageous biocatalysts.

Thermally robust solvent-free biofluids of M13 bacteriophage engineered for high compatibility with anhydrous ionic liquids

Soft materials typically lack structural complexity. Chemically modifying viruses can produce biomaterials with added functionality that overcome this limitation.

Insight into the molecular mechanism behind PEG-mediated stabilization of biofluid lipases

Bioconjugates established between anionic polyethylene glycol (PEG) based polymers and cationic proteins have proven to be a promising strategy to engineer thermostable biocatalysts. However, the enzyme activity of these bioconjugates is very low and the mechanism of non-covalent PEG-stabilization is yet to be understood. This work presents experimental and molecular dynamics simulation studies, using lipase-polymer surfactant nanoconjugates from mesophile Rhizomucor miehei (RML), performed to evaluate the effect of PEG on enzyme stability and activity. Results demonstrated that the number of hydrogen bonds between the cationized RML and PEG chain correlates with enzyme thermostability. In addition, an increase of both the number of PEG-polymers units and cationization degree of the enzyme leads to a decrease of enzyme activity. Modelling with SAXS data of aqueous solutions of the biofluid lipases agrees with previous hypothesis that these enzymes contain a core constituted of folded protein confined by a shell of surfactants. Together results provide valuable insight into the mechanism of non-covalent PEG mediated protein stabilization relevant for engineering active and thermostable biofluids. Furthermore, the first biofluids RML with activity comparable to their cationized counterpart are presented.

Probing Adsorption Behaviors of BSA onto Chiral Surfaces of Nanoparticles

Chiral properties of nanoscale materials are of importance as they dominate interactions with proteins in physiological environments; however, they have rarely been investigated. In this study, a systematic investigation is conducted for the adsorption behaviors of bovine serum albumin (BSA) onto the chiral surfaces of gold nanoparticles (AuNPs), involving multiple techniques and molecular dynamic (MD) simulation. The adsorption of BSA onto both L- and D-chiral surfaces of AuNPs shows discernible differences involving thermodynamics, adsorption orientation, exposed charges, and affinity. As a powerful supplement, MD simulation provides a molecular-level understanding of protein adsorption onto nanochiral surfaces. Salt bridge interaction is proposed as a major driving force at protein-nanochiral interface interaction. The spatial distribution features of functional groups (COO^- , NH₃⁺ , and CH₃ ) of chiral molecules on the nanosurface play a key role in the formation and location of salt bridges, which determine the BSA adsorption orientation and binding strength to chiral surfaces. Sequentially, BSA corona coated on nanochiral surfaces affects their uptake by cells. The results enhance the understanding of protein corona, which are important for biological effects of nanochirality in living organisms.

BrisSynBio: a BBSRC/EPSRC-funded Synthetic Biology Research Centre

BrisSynBio is the Bristol-based Biotechnology and Biological Sciences Research Council (BBSRC)/Engineering and Physical Sciences Research Council (EPSRC)-funded Synthetic Biology Research Centre. It is one of six such Centres in the U.K. BrisSynBio's emphasis is on rational and predictive bimolecular modelling, design and engineering in the context of synthetic biology. It trains the next generation of synthetic biologists in these approaches, to facilitate translation of fundamental synthetic biology research to industry and the clinic, and to do this within an innovative and responsible research framework.

Strategies for cell membrane functionalization

The ability to rationally manipulate and augment the cytoplasmic membrane can be used to overcome many of the challenges faced by conventional cellular therapies and provide innovative opportunities when combined with new biotechnologies. The focus of this review is on emerging strategies used in cell functionalization, highlighting both pioneering approaches and recent developments. These will be discussed within the context of future directions in this rapidly evolving field.

Liquefaction of Biopolymers: Solvent-free Liquids and Liquid Crystals from Nucleic Acids and Proteins

Biomacromolecules, such as nucleic acids, proteins, and virus particles, are persistent molecular entities with dimensions that exceed the range of their intermolecular forces hence undergoing degradation by thermally induced bond-scission upon heating. Consequently, for this type of molecule, the absence of a liquid phase can be regarded as a general phenomenon. However, certain advantageous properties usually associated with the liquid state of matter, such as processability, flowability, or molecular mobility, are highly sought-after features for biomacromolecules in a solvent-free environment. Here, we provide an overview over the design principles and synthetic pathways to obtain solvent-free liquids of biomacromolecular architectures approaching the topic from our own perspective of research. We will highlight the milestones in synthesis, including a recently developed general surfactant complexation method applicable to a large variety of biomacromolecules as well as other synthetic principles granting access to electrostatically complexed proteins and DNA.

These synthetic pathways retain the function and structure of the biomacromolecules even under extreme, nonphysiological conditions at high temperatures in water-free melts challenging the existing paradigm on the role of hydration in structural biology. Under these conditions, the resulting complexes reveal their true potential for previously unthinkable applications. Moreover, these protocols open a pathway toward the assembly of anisotropic architectures, enabling the formation of solvent-free biomacromolecular thermotropic liquid crystals. These ordered biomaterials exhibit vastly different mechanical properties when compared to the individual building blocks. Beyond the preparative aspects, we will shine light on the unique potential applications and technologies resulting from solvent-free biomacromolecular fluids: From charge transport in dehydrated liquids to DNA electrochromism to biocatalysis in the absence of a protein hydration shell. Moreover, solvent-free biological liquids containing viruses can be used as novel storage and process media serving as a formulation technology for the delivery of highly concentrated bioactive compounds. We are confident that this new class of hybrid biomaterials will fuel further studies and applications of biomacromolecules beyond water and other solvents and in a much broader context than just the traditional physiological conditions.

Direct folding simulation of helical proteins using an effective polarizable bond force field

Snapshots of the intermediate conformation of Trp-cage at various simulation times using AMBER03, EPB03, AMBER12SB, and EPB12SB. Here, the N terminal is always on the top.

Effect of electrostatic polarization and bridging water on CDK2–ligand binding affinities calculated using a highly efficient interaction entropy method

A new highly efficient interaction entropy (IE) method combined with the polarized protein-specific charge (PPC) force field is employed to investigate the interaction mechanism of CDK2–ligand binding and the effect of the bridging water.

Surface Structure of Hydroxyapatite from Simulated Annealing Molecular Dynamics Simulations

The surface structure of hydroxyapatite (HAP) is crucial for its bioactivity. Using a molecular dynamics simulated annealing method, we studied the structure and its variation with annealing temperature of the HAP (100) surface. In contrast to the commonly used HAP surface model, which is sliced from HAP crystal and then relaxed at 0 K with first-principles or force-field calculations, a new surface structure with gradual changes from ordered inside to disordered on the surface was revealed. The disordering is dependent on the annealing temperature, Tmax. When Tmax increases up to the melting point, which was usually adopted in experiments, the disordering increases, as reflected by its radial distribution functions, structural factors, and atomic coordination numbers. The disordering of annealed structures does not show significant changes when Tmax is above the melting point. The thickness of disordered layers is about 10 Å. The surface energy of the annealed structures at high temperature is significantly less than that of the crystal structure relaxed at room temperature. A three-layer model of interior, middle, and surface was then proposed to describe the surface structure of HAP. The interior layer retains the atomic configurations in crystal. The middle layer has its atoms moved and its groups rotated about their original locations. In the surface layer, the atomic arrangements are totally different from those in crystal. In particular for the hydroxyl groups, they move outward and cover the Ca(2+) ions, leaving holes occupied by the phosphate groups. Our study suggested a new model with disordered surface structures for studying the interaction of HAP-based biomaterials with other molecules.

Tobacco Mosaic Virus-Based 1D Nanorod-Drug Carrier via the Integrin-Mediated Endocytosis Pathway

For cancer therapy, viruses have been utilized as excellent delivery vehicles because of their facile transfection efficiency in their host cells. However, their inherent immunogenicity has become the major obstacle for their translation into approved pharmaceuticals. Herein, we utilized rodlike plant virus, tobacco mosaic virus (TMV), which is nontoxic to mammals and mainly infects tobacco species, as anticancer nanorod-drug vector for cancer therapy study. Doxorubicin (DOX) was installed in the inner cavity of TMV by hydrazone bond, which enabled the pH-sensitive drug release property. Conjugation of cyclic Arg-Gly-Asp (cRGD) on the surface of TMV can enhance HeLa cell uptake of the carrier via the integrin-mediated endocytosis pathway. Comparing with free DOX, the cRGD-TMV-hydra-DOX vector had similar cell growth inhibition and much higher apoptosis efficiency on HeLa cells. Moreover, the in vivo assay assumed that cRGD-TMV-hydra-DOX behaved similar antitumor efficiency but much lower side effect on HeLa bearing Balb/c-nu mice. Our work provides novel insights into potentially cancer therapy based on rodlike plant viral nanocarriers.

Solubilizing and Stabilizing Proteins in Anhydrous Ionic Liquids through Formation of Protein-Polymer Surfactant Nanoconstructs

Nonaqueous biocatalysis is rapidly becoming a desirable tool for chemical and fuel synthesis in both the laboratory and industry. Similarly, ionic liquids are increasingly popular anhydrous reaction media for a number of industrial processes. Consequently, the use of enzymes in ionic liquids as efficient, environment-friendly, commercial biocatalysts is highly attractive. However, issues surrounding the poor solubility and low stability of enzymes in truly anhydrous media remain a significant challenge. Here, we demonstrate for the first time that engineering the surface of a protein to yield protein-polymer surfactant nanoconstructs allows for dissolution of dry protein into dry ionic liquids. Using myoglobin as a model protein, we show that this method can deliver protein molecules with near native structure into both hydrophilic and hydrophobic anhydrous ionic liquids. Remarkably, using temperature-dependent synchrotron radiation circular dichroism spectroscopy to measure half-denaturation temperatures, our results show that protein stability increases by 55 °C in the ionic liquid as compared to aqueous solution, pushing the solution thermal denaturation beyond the boiling point of water. Therefore, the work presented herein could provide a platform for the realization of biocatalysis at high temperatures or in anhydrous solvent systems.