Bacterially Grown Cellulose/Graphene Oxide Composites Infused with γ-Poly (Glutamic Acid) as Biodegradable Structural Materials with Enhanced Toughness

Bioinspired bacterial cellulose (BC) composites are next-generation renewable materials that exhibit promising industrial applications. However, large-scale production of inorganic/organic BC composites by in situ fermentation remains difficult. The methods based on BC mechanical disintegration impair the mechanical property of dried BC films, while the static in situ fermentation methods fail to incorporate inorganic particles within the BC network because of the limited diffusion ability. Furthermore, the addition of other components in the fermentation medium significantly interferes with the production of BC. Here, a tough BC composite with a layered structure reminiscent of the tough materials found in nature (e.g., nacre, dentin, and bone) is prepared using a semistatic in situ fermentation method. The bacterially produced biopolymer γ-poly(glutamic acid) (PGA), together with graphene oxide (GO), is introduced into the BC fermentation medium. The resulting dried BC-GO-PGA composite film shows high toughness (36 MJ m-3), which makes it one of the toughest BC composite film reported. In traditional in situ fermentation methods, the addition of a second component significantly reduces the wet thickness of the final composites. However, in this report, we show that addition of both PGA and GO to the fermentation medium shows a synergistic effect in increasing the wet thickness of the final BC composites. By gently agitating the solution, GO particles get entrapped into the BC network, as the formed pellicles can move below the liquid level and the GO particles suspended in the liquid can be entrapped into the BC network. Compared to other methods, this method achieves high toughness while using a mild and easily scalable fabrication procedure. These bacterially produced composites could be employed in the next generation of biodegradable structural high-performance materials, construction materials, and tissue engineering scaffolds (tendon, ligament, and skin) that require high toughness. BN/Marie-Eve Aubin-Tam La

Bioprinting of Regenerative Photosynthetic Living Materials

Living materials, which are fabricated by encapsulating living biological cells within a non-living matrix, have gained increasing attention in recent years. Their fabrication in spatially defined patterns that are mechanically robust is essential for their optimal functional performance but is difficult to achieve. Here, a bioprinting technique employing environmentally friendly chemistry to encapsulate microalgae within an alginate hydrogel matrix is reported. The bioprinted photosynthetic structures adopt pre-designed geometries at millimeter-scale resolution. A bacterial cellulose substrate confers exceptional advantages to this living material, including strength, toughness, flexibility, robustness, and retention of physical integrity against extreme physical distortions. The bioprinted materials possess sufficient mechanical strength to be self-standing, and can be detached and reattached onto different surfaces. Bioprinted materials can survive stably for a period of at least 3 days without nutrients, and their life can be further extended by transferring them to a fresh source of nutrients within this timeframe. These bioprints are regenerative, that is, they can be reused and expanded to print additional living materials. The fabrication of the bioprinted living materials can be readily up-scaled (up to ≥70 cm × 20 cm), highlighting their potential product applications including artificial leaves, photosynthetic bio-garments, and adhesive labels.</p

Mechanochemical basis of protein degradation by a double-ring AAA+ machine

Molecular machines containing double or single AAA+ rings power energy-dependent protein degradation and other critical cellular processes, including disaggregation and remodeling of macromolecular complexes. How the mechanical activities of double-ring and single-ring AAA+ enzymes differ is unknown. Using single-molecule optical trapping, we determine how the double-ring ​ClpA enzyme from Escherichia coli, in complex with the ​ClpP peptidase, mechanically degrades proteins. We demonstrate that ​ClpA unfolds some protein substrates substantially faster than does the single-ring ​ClpX enzyme, which also degrades substrates in collaboration with ​ClpP. We find that ​ClpA is a slower polypeptide translocase and that it moves in physical steps that are smaller and more regular than steps taken by ​ClpX. These direct measurements of protein unfolding and translocation define the core mechanochemical behavior of a double-ring AAA+ machine and provide insight into the degradation of proteins that unfold via metastable intermediates.Howard Hughes Medical InstituteNational Institutes of Health (U.S.) (Grant AI-16892

Subunit asymmetry and roles of conformational switching in the hexameric AAA+ ring of ClpX

The hexameric AAA+ ring of Escherichia coli ClpX, an ATP-dependent machine for protein unfolding and translocation, functions with the ClpP peptidase to degrade target substrates. For efficient function, ClpX subunits must switch between nucleotide-loadable (L) and nucleotide-unloadable (U) conformations, but the roles of switching are uncertain. Moreover, it is controversial whether working AAA+-ring enzymes assume symmetric or asymmetric conformations. Here, we show that a covalent ClpX ring with one subunit locked in the U conformation catalyzes robust ATP hydrolysis, with each unlocked subunit able to bind and hydrolyze ATP, albeit with highly asymmetric position-specific affinities. Preventing U↔L interconversion in one subunit alters the cooperativity of ATP hydrolysis and reduces the efficiency of substrate binding, unfolding and degradation, showing that conformational switching enhances multiple aspects of wild-type ClpX function. These results support an asymmetric and probabilistic model of AAA+-ring activity.National Institutes of Health (U.S.) (Grant GM-101988)Massachusetts Institute of Technology (Poitras Predoctoral Fellowship

Application of isothermal titration calorimetry in evaluation of protein–nanoparticle interactions

Nanoparticles (NPs) offer a number of advantages over small organic molecules for controlling protein behaviour inside the cell. Protein binding to the surface of NPs depends on their surface characteristics, composition and method of preparation (Mandal et al. in J Hazard Mater 248–249:238–245, 2013). It is important to understand the binding affinities, stoichiometries and thermodynamical parameters of NP–protein interactions in order to see which interaction will have toxic and hazardous consequences and thus to prevent it. On the other side, because proteins are on the brink of stability, they may experience interactions with some types of NPs that are strong enough to cause denaturation or significantly change their conformations with concomitant loss of their biological function. Structural changes in the protein may cause exposure of new antigenic sites, “cryptic” peptide epitopes, potentially triggering an immune response which can promote autoimmune disease (Treuel et al. in ACS Nano 8(1):503–513, 2014). Mechanistic details of protein structural changes at NP surface have still remained elusive. Understanding the formation and persistence of the protein corona is critical issue; however, there are no many analytical methods which could provide detailed information about the NP–protein interaction characteristics and about protein structural changes caused by interactions with nanoparticles. The article reviews recent studies in NP–protein interactions research and application of isothermal titration calorimetry (ITC) in this research. The study of protein structural changes upon adsorption on nanoparticle surface and application of ITC in these studies is emphasized. The data illustrate that ITC is a versatile tool for evaluation of interactions between NPs and proteins. When coupled with other analytical methods, it is important analytical tool for monitoring conformational changes in proteins

Modular assembly of proteins on nanoparticles

Generally, the high diversity of protein properties necessitates the development of unique nanoparticle bio-conjugation methods, optimized for each different protein. Here we describe a universal bio-conjugation approach which makes use of a new recombinant fusion protein combining two distinct domains. The N-terminal part is Glutathione S-Transferase (GST) from Schistosoma japonicum, for which we identify and characterize the remarkable ability to bind gold nanoparticles (GNPs) by forming gold–sulfur bonds (Au–S). The C-terminal part of this multi-domain construct is the SpyCatcher from Streptococcus pyogenes, which provides the ability to capture recombinant proteins encoding a SpyTag. Here we show that SpyCatcher can be immobilized covalently on GNPs through GST without the loss of its full functionality. We then show that GST-SpyCatcher activated particles are able to covalently bind a SpyTag modified protein by simple mixing, through the spontaneous formation of an unusual isopeptide bond

Observation of the diphoton decay of the Higgs boson and measurement of its properties

Peer reviewe

Precise determination of the mass of the Higgs boson and tests of compatibility of its couplings with the standard model predictions using proton collisions at 7 and 8 TeV

Peer reviewe

Search for Dark Matter and Supersymmetry with a Compressed Mass Spectrum in the Vector Boson Fusion Topology in Proton-Proton Collisions at root s=8 TeV

Peer reviewe

Measurement of the production cross section ratio σ(χb2(1P))/σ(χb1(1P))in pp collisions at √s=8TeV

A measurement of the production cross section ratio σ(χb2(1P))/σ(χb1(1P))σ(χb2(1P))/σ(χb1(1P)) is presented. The χb1(1P)χb1(1P) and χb2(1P)χb2(1P) bottomonium states, promptly produced in pp collisions at View the MathML sources=8 TeV, are detected by the CMS experiment at the CERN LHC through their radiative decays χb1,2(1P)→ϒ(1S)+γχb1,2(1P)→ϒ(1S)+γ. The emitted photons are measured through their conversion to e+e−e+e− pairs, whose reconstruction allows the two states to be resolved. The ϒ(1S)ϒ(1S) is measured through its decay to two muons. An event sample corresponding to an integrated luminosity of 20.7 fb−120.7 fb−1 is used to measure the cross section ratio in a phase-space region defined by the photon pseudorapidity, |ηγ|<1.0|ηγ|<1.0; the ϒ(1S)ϒ(1S) rapidity, |yϒ|<1.5|yϒ|<1.5; and the ϒ(1S)ϒ(1S) transverse momentum, View the MathML source7<pTϒ<40 GeV. The cross section ratio shows no significant dependence on the ϒ(1S)ϒ(1S) transverse momentum, with a measured average value of View the MathML source0.85±0.07(stat+syst)±0.08(BF), where the first uncertainty is the combination of the experimental statistical and systematic uncertainties and the second is from the uncertainty in the ratio of the χbχb branching fractions