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SilE and SilB are both proteins involved in the silver efflux pump found in Gram-negative bacteria such as S. typhimurium. Using model peptides along with NMR and CD experiments, we show how SilE may store silver ions prior to delivery and we hypothesize for the first time the interplay between SilB and SilE.

Anaerobic microorganisms of the Geobacter genus are effective electron sources for the synthesis of nanoparticles, for bioremediation of polluted water, and for the production of electricity in fuel cells. In multistep reactions, electrons are transferred via iron/heme cofactors of c-type cytochromes from the inner cell membrane to extracellular metal ions, which are bound to outer membrane cytochromes. We measured electron production and electron flux rates to 5×10 5  e s -1 per G. sulfurreducens. Remarkably, these rates are independent of the oxidants, and follow zero order kinetics. It turned out that the microorganisms regulate electron flux rates by increasing their Fe 2+ /Fe 3+ ratios in the multiheme cytochromes whenever the activity of the extracellular metal oxidants is diminished. By this mechanism the respiration remains constant even when oxidizing conditions are changing. This homeostasis is a vital condition for living systems, and makes G. sulfurreducens a versatile electron source., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The binding of lanthanide containers [Ln(β-diketonate) 3 dig] [dig = 1-methoxy-2-(2-methoxyethoxy)ethane] to aromatic tridentate N-donor ligands ( L ) in dichloromethane produces neutral nine-coordinate heteroleptic [ L Ln(β-diketonate) 3 ] complexes, the equilibrium reaction quotients of which vary with the total concentrations of the reacting partners. This problematic drift prevents the determination of both reliable thermodynamic stability constants and intrinsic host-guest affinities. The classical solution theory assigns this behavior to changes in the activity coefficients of the various partners in nonideal solutions, and a phenomenological approach attempts to quantitatively attribute this effect to some partition of the solvent molecules between bulk-innocent and contact-noninnocent contributors to the chemical potential. This assumption eventually predicts an empirical linear dependence of the equilibrium reaction quotient on the concentration of the formed [ L Ln(β-diketonate) 3 ] complexes, a trend experimentally supported in this contribution for various ligands L differing in lipophilicity and nuclearity and for lanthanide containers grafted with diverse β-diketonate coligands. Even if the origin of the latter linear dependence is still the subject of debate, this work demonstrates that this approach can be exploited by experimentalists for extracting reliable thermodynamic constants suitable for analyzing and comparing host-guest affinities in organic solvents.

Here, we show by solution nuclear magnetic resonance measurements that the urea-unfolded protein apoazurin becomes elongated when the synthetic crowding agent dextran 20 is present, in contrast to the prediction from the macromolecular crowding effect based on the argument of volume exclusion. To explore the complex interactions beyond volume exclusion, we employed coarse-grained molecular dynamics simulations to explore the conformational ensemble of apoazurin in a box of monodisperse crowders under strong chemically denaturing conditions. The elongated conformation of unfolded apoazurin appears to result from the interplay of the effective attraction between the protein and crowders and the shape of the crowders. With a volume-conserving crowder model, we show that the crowder shape provides an anisotropic direction of the depletion force, in which a bundle of surrounding rodlike crowders stabilize an elongated conformation of unfolded apoazurin in the presence of effective attraction between the protein and crowders.

Impairment or stimulation of the immune system by ionizing radiation (IR) impacts on immune surveillance of tumor cells and non-malignant cells and can either foster therapy response or side effects/toxicities of radiation therapy. For a better understanding of the mechanisms by which IR modulates T-cell activation and alters functional properties of these immune cells, we exposed human immortalized Jurkat cells and peripheral blood lymphocytes (PBL) to X-ray doses between 0.1 and 5 Gy. This resulted in cellular responses, which are typically observed also in naïve T-lymphocytes in response of T-cell receptor immune stimulation or mitogens. These responses include oscillations of cytosolic Ca 2+ , an upregulation of CD25 surface expression, interleukin-2 and interferon-γ synthesis, elevated expression of Ca 2+ sensitive K + channels and an increase in cell diameter. The latter was sensitive to inhibition by the immunosuppressant cyclosporine A, Ca 2+ buffer BAPTA-AM, and the CDK1-inhibitor RO3306, indicating the involvement of Ca 2+ -dependent immune activation and radiation-induced cell cycle arrest. Furthermore, on a functional level, Jurkat and PBL cell adhesion to endothelial cells was increased upon radiation exposure and was highly dependent on an upregulation of integrin beta-1 expression and clustering. In conclusion, we here report that IR impacts on immune activation and functional properties of T-lymphocytes that may have implications in both toxic effects and treatment response to combined radiation and immune therapy in cancer patients.

Since its identification as an independent topic after the first world war, the chemistry of (bio)polymers and macromolecules rapidly benefited from intense synthetic activities driven by contributors focusing on formulation and structural aspects. Satisfying rationalization and predictions concerning polymer organization, stability, and reactivity were, however, delayed until the late fifties, when physical chemists set the basis of an adapted thermodynamic modeling. The recent emergence of metal-containing (bio)organic polymers (i.e., metallopolymers) thus corresponds to a logical extension of this field with the ultimate goal of combining the rich magnetic and optical properties of open-shell transition metals with the processability and structural variety of polymeric organic scaffolds. Since applications as energy storage materials, drug delivery vectors, shape-memory materials, and photonic devices can be easily envisioned for these materials, the development of metallopolymers is faced with some urgency in producing novel exploitable structures, while the rational control of their formation, organization, and transformation remains elusive. Caught between the sometimes antagonistic requirements of economic efficiency on one side and of scientific pertinence on the other side, the ongoing achievements in the control of the metal loadings of multi-site polymers are highlighted here with some tutorial discussions of luminescent lanthanidopolymers as proof-of-concept., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Objective: Adhesion of cells to the extracellular matrix is facilitated by integrin receptors. We recently found that a nanoscale organization of plasma membrane located integrins containing the β1 subunit is responsible for an enhanced radio-resistance in 3D cultured cells over cells grown in 2D. While ionizing radiation is known to have broad effects on the lipid composition of the plasma membrane and their organization in lipid-rafts, it is not clear whether the effects of ionizing radiation on the nanoscale clustering of integrins is lipid-raft dependent., Results: Using single molecule microscopy we can show that β1 integrins colocalize with cholesterol in lipid-rafts. Ionizing radiation, as an extrinsic stressor, causes the separation of β1 integrins from cholesterol lipid raft suggesting that the effects of ionizing radiation on the clustering of β1 integrins are lipid-raft independent.

Metal-containing (bio)organic polymers are materials of continuously increasing importance for applications in energy storage and conversion, drug delivery, shape-memory items, supported catalysts, organic conductors and smart photonic devices. The embodiment of luminescent components provides a revolution in lighting and signaling with the ever-increasing development of polymeric light-emitting devices. Despite the unique properties expected from the introduction of optically and magnetically active lanthanides into organic polymers, the deficient control of the metal loading currently limits their design to empirical and poorly reproducible materials. We show here that the synthetic efforts required for producing soluble multi-site host systems L k are largely overcome by the virtue of reversible thermodynamics for mastering the metal loading with the help of only two parameters: (1) the affinity of the luminescent lanthanide container for a single binding site and (2) the cooperative effect which modulates the successive fixation of metallic units to adjacent sites. When unsymmetrical perfluorobenzene-trifluoroacetylacetonate co-ligands (pbta - ) are selected for balancing the charge of the trivalent lanthanide cations, Ln 3+ , in six-coordinate [Ln(pbta) 3 ] containers, the explored anti-cooperative complexation processes induce nearest-neighbor intermetallic interactions twice as large as thermal energy at room temperature ( RT = 2.5 kJ mol -1 ). These values have no precedent when using standard symmetrical containers and they pave the way for programming metal alternation in luminescent lanthanidopolymers.

The cellular interaction with the extracellular matrix (ECM) modulates many key processes such as proliferation, migration, differentiation and survival. In addition, cells cultured under 3D conditions in presence of an ECM display a marked radioresistance towards ionizing radiation (IR) in comparison to conventionally 2D cultured cells. This process, also known as "cell-adhesion-mediated-radio-resistance" (CAM-RR), has been linked to the chromatin structure that differs between cells cultured on stiff surfaces versus cell grown on soft planar supports or in 3D environments. As integrins are the key mediators of cell adhesion and mechanosensing, they originate the molecular signalling towards chromatin remodelling in response to a cell's microenvironment. We aimed to investigate this molecular origin that leads to CAM-RR by investigating the distribution of integrins at the single molecule level and show that cells cultured in 2D keep a lower fraction of integrin β1 in clusters and maintain a less defined cluster status than 3D cultured cells. Upon X-irradiation this nanoscale distribution of integrin β1 is disturbed at much lower dosages in 2D versus 3D cultured cells. Radioresistance is thus linked to the ability to maintain a well defined organization of integrins in clusters, making integrin distribution a potential drug target for radiosensitization.

Cells of multicellular organisms are surrounded by and attached to a matrix of fibrous polysaccharides and proteins known as the extracellular matrix. This fibrous network not only serves as a structural support to cells and tissues but also plays an integral part in the process as important as proliferation, differentiation, or defense. While at first sight, the extracellular matrices of plant and animals do not have much in common, a closer look reveals remarkable similarities. In particular, the proteins involved in the adhesion of the cell to the extracellular matrix share many functional properties. At the sequence level, however, a surprising lack of homology is found between adhesion-related proteins of plants and animals. Both protein machineries only reveal similarities between small subdomains and motifs, which further underlines their functional relationship. In this review, we provide an overview on the similarities between motifs in proteins known to be located at the plant cell wall-plasma membrane-cytoskeleton interface to proteins of the animal adhesome. We also show that by comparing the proteome of both adhesion machineries at the level of motifs, we are also able to identify potentially new candidate proteins that functionally contribute to the adhesion of the plant plasma membrane to the cell wall.

The basic concept of allosteric cooperativity used in biology, chemistry and physics states that any change in the intermolecular host-guest interactions operating in multisite receptors can be assigned to intersite interactions. Using lanthanide metals as guests and linear multi-tridentate linear oligomers of variable lengths and geometries as hosts, this work shows that the quantitative modeling of metal loadings requires the consideration of a novel phenomenon originating from solvation processes. It stepwise modulates the intrinsic affinity of each isolated site in multisite receptors, and this without resorting to allosteric cooperativity. An easy-to-handle additive model predicts a negative power law dependence of the intrinsic affinity on the length of the linear metallopolymer. Applied to lanthanidopolymers, the latter common analysis overestimates cooperativity factors by more than two orders of magnitude., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

This work demonstrates how the thermodynamic loading of monodisperse polymeric single-stranded multi-tridentate receptors of variable lengths is controlled by the nature of the metallic carrier Ln(hfac)3 (Ln is La, Eu or Y, and hfac is hexafluoroacetylacetonate). Whereas the intrinsic affinity of the tridentate binding site is maximum for medium-sized Eu(3+) and decreases for Y(3+), the contraction of the hydrodynamic radius of the polymer upon metal loading induces positive allosteric cooperativity for the smaller cations. The origin of this behaviour is rationalized within the frame of intermetallic dipole-dipole interactions modulated by the solvation potential of dipolar solutes in dielectric materials. Positive cooperativity produces local high-density of metal ions along the ligand strands (metal clustering) with potential interest in energy migration and sensing processes.

The properties of paper sheets can be tuned by adjusting the surface or bulk chemistry using functional polymers that are applied during (online) or after (offline) papermaking processes. In particular, polymers are widely used to enhance the mechanical strength of the wet state of paper sheets. However, the mechanical strength depends not only on the chemical nature of the polymeric additives but also on the distribution of the polymer on and in the lignocellulosic paper. Here, we analyze the photochemical attachment and distribution of hydrophilic polydimethylacrylamide-co-methacrylate-benzophenone P(DMAA-co-MABP) copolymers with defined amounts of photoreactive benzophenone moieties in model paper sheets. Raman microscopy was used for the unambiguous identification of P(DMAA-co-MABP) and cellulose specific bands and thus the copolymer distribution within the cellulose matrix. Two-dimensional Raman spectral maps at the intersections of overlapping cellulose fibers document that the macromolecules only partially surround the cellulose fibers, favor to attach to the fiber surface, and connect the cellulose fibers at crossings. Moreover, the copolymer appears to accumulate preferentially in holes, vacancies, and dips on the cellulose fiber surface. Correlative brightfield, Raman, and confocal laser scanning microscopy finally reveal a reticular three-dimensional distribution of the polymer and show that the polymer is predominately deposited in regions of high capillarity (i.e., in proximity to fine cellulose fibrils). These data provide deeper insights into the effects of paper functionalization with a copolymer and aid in understanding how these agents ultimately influence the local and overall properties of paper.

This work illustrates the use of basic statistical mechanics for rationalizing the loading of linear multitridentate polymers with trivalent lanthanides, Ln(III), and identifies the specific ionic sizes of europium and yttrium as promising candidates for the further design of organized heterometallic f–f′ materials. Using [Ln(hfac)3] (hfac = hexafluoroacetylacetonate) as lanthanide carriers, the thermodynamically controlled formation of Wolf type-II lanthanidopolymers [{Ln(hfac)3}m(L4)] is modeled with the help of two simple microscopic descriptors: (i) the intrinsic affinity of Ln(III) for the tridentate binding sites fN3(Ln) and (ii) the intermetallic interactions ΔE1–2(Ln,Ln) operating between two occupied adjacent sites. Selective complexation (fN3La << fN3Eu > fN3(Y)) modulated by anticooperative interactions (ΔE1–2(La,La) ≃ ΔE1–2(Eu,Eu) > ΔE1–2(Y,Y) ≈ 0) favors the fixation of Eu(III) in semiorganized lanthanidopolymers [{Eu(hfac)3}m(L4)] displaying exploitable light-downshifting.

Transfer news: the use of a simple method allows the various sensitization steps in Eu(III) -containing complexes to be deciphered. Incorporation of an increasing number of electron-withdrawing fluorine atoms on the rigid and electronically tunable phenyl spacer between two tridentate binding units (see picture, red O, dark blue N) affects the quantum yield, intersystem crossing, and energy-transfer processes in a rational way., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Atherosclerosis results in the narrowing of arterial blood vessels and this causes significant changes in the endogenous shear stress between healthy and constricted arteries. Nanocontainers that can release drugs locally with such rheological changes can be very useful. Here, we show that vesicles made from an artificial 1,3-diaminophospholipid are stable under static conditions but release their contents at elevated shear stress. These vesicles have a lenticular morphology, which potentially leads to instabilities along their equator. Using a model cardiovascular system based on polymer tubes and an external pump to represent shear stress in healthy and constricted vessels of the heart, we show that drugs preferentially release from the vesicles in constricted vessels that have high shear stress.

The first asymmetric Cu-catalyzed conjugate addition of dialkylzinc zinc reagents to a large scope of enals in presence of phosphoramidite, SimplePhos, or (R)-BINAP ligands with enantiomeric excesses up to 90% is reported. Moreover, ACA of Grignard reagents afforded moderate to good 1,4-regioselectivities with enantioselectivities up to 90%.