Showing papers on "Chemical binding published in 2013"
TL;DR: There is a need to systematically investigate the bioavailability of omega-3 fatty acids formulations, which might be a key to designing more effective studies in the future.
Abstract: Supplements have reached a prominent role in improving the supply of long-chain omega-3 fatty acids, such as Eicosapentaenoic acid (EPA 20:5n-3) and Docosahexaenoic acid (DHA 22:6n-3). Similar to other nutrients, the availability of omega-3 fatty acids is highly variable and determined by numerous factors. However, the question of omega-3 fatty acids bioavailability has long been disregarded, which may have contributed to the neutral or negative results concerning their effects in several studies. This review provides an overview of the influence of chemical binding form (free fatty acids bound in ethylesters, triacylglycerides or phospholipids), matrix effects (capsule ingestion with concomitant intake of food, fat content in food) or galenic form (i.e. microencapsulation, emulsification) on the bioavailability of omega-3 fatty acids. There is a need to systematically investigate the bioavailability of omega-3 fatty acids formulations, which might be a key to designing more effective studies in the future.
271 citations
TL;DR: PLGA nanoparticles modified by chitosan showed versatility of surface and a possible improvement in the efficacy of current PLGA-based drug delivery system.
Abstract: Shortage of functional groups on surface of poly(lactide-co-glycolide) (PLGA)-based drug delivery carriers always hampers its wide applications such as passive targeting and conjugation with targeting molecules. In this research, PLGA nanoparticles were modified with chitosan through physical adsorption and chemical binding methods. The surface charges were regulated by altering pH value in chitosan solutions. After the introduction of chitosan, zeta potential of the PLGA nanoparticle surface changed from negative charge to positive one, making the drug carriers more affinity to cancer cells. Functional groups were compared between PLGA nanoparticles and chitosan-modified PLGA nanoparticles. Amine groups were exhibited on PLGA nanoparticle surface after the chitosan modification as confirmed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The modified nanoparticles showed an initial burst release followed by a moderate and sustained release profile. Higher percentage of drugs from cumulative release can be achieved in the same prolonged time range. Therefore, PLGA nanoparticles modified by chitosan showed versatility of surface and a possible improvement in the efficacy of current PLGA-based drug delivery system.
223 citations
TL;DR: Experimental results support O-O bond formation between O5 and possibly an oxyl radical as proposed by Siegbahn and exclude W1 as the second substrate water.
Abstract: The assignment of the two substrate water sites of the tetra-manganese penta-oxygen calcium (Mn4O5Ca) cluster of photosystem II is essential for the elucidation of the mechanism of biological O-O bond formation and the subsequent design of bio-inspired water-splitting catalysts. We recently demonstrated using pulsed EPR spectroscopy that one of the five oxygen bridges (μ-oxo) exchanges unusually rapidly with bulk water and is thus a likely candidate for one of the substrates. Ammonia, a water analog, was previously shown to bind to the Mn4O5Ca cluster, potentially displacing a water/substrate ligand [Britt RD, et al. (1989) J Am Chem Soc 111(10):3522–3532]. Here we show by a combination of EPR and time-resolved membrane inlet mass spectrometry that the binding of ammonia perturbs the exchangeable μ-oxo bridge without drastically altering the binding/exchange kinetics of the two substrates. In combination with broken-symmetry density functional theory, our results show that (i) the exchangable μ-oxo bridge is O5 {using the labeling of the current crystal structure [Umena Y, et al. (2011) Nature 473(7345):55–60]}; (ii) ammonia displaces a water ligand to the outer manganese (MnA4-W1); and (iii) as W1 is trans to O5, ammonia binding elongates the MnA4-O5 bond, leading to the perturbation of the μ-oxo bridge resonance and to a small change in the water exchange rates. These experimental results support O-O bond formation between O5 and possibly an oxyl radical as proposed by Siegbahn and exclude W1 as the second substrate water.
138 citations
TL;DR: The results provide the first evidence for release of bound residues during alteration of the redox environment and indicate that sequential anoxic-oxic incubation approaches-considered effective in remediation of environments containing halogenated xenobiotics-do not completely remove Xenobiotics from environmental matrices.
Abstract: Tetrabromobisphenol A (TBBPA) is one of the most commonly used flame retardants and has become an environmental contaminant worldwide We studied the fate of (14)C-labeled TBBPA in soil under static anoxic (195 days) and sequential anoxic (125 days)-oxic (70 days) conditions During anoxic incubation, TBBPA dissipated with a half-life of 36 days, yielding four debromination metabolites: bisphenol A (BPA) and mono-, di-, and tribrominated BPA At the end of anoxic incubation, all four brominated BPAs completely disappeared, leaving BPA (54% of initial TBBPA) as the sole detectable organic metabolite TBBPA dissipation was accompanied by trace mineralization (<13%) and substantial bound-residue formation (35%), probably owing to chemical binding to soil organic matter Subsequent oxic incubation was effective in degrading accumulated BPA (half-life 11 days) through mineralization (6%) and bound-residue formation (62%) However, 42% of the anoxically formed bound residues was released as TBBPA and lower brominated BPAs, which were then persistent during oxic incubation Our results provide the first evidence for release of bound residues during alteration of the redox environment and indicate that sequential anoxic-oxic incubation approaches-considered effective in remediation of environments containing halogenated xenobiotics-do not completely remove xenobiotics from environmental matrices
123 citations
TL;DR: The efficient synthesis is reported here the efficient synthesis of 4,4'-bis(diethylphosphonomethyl)-2,2'-bipyridine and 4,2-bis( diethylPhosphonate)-2-bipiridine, as well as the mono-, bis-, and tris-substituted ruthenium complexes.
Abstract: Water-stable, surface-bound chromophores, catalysts, and assemblies are an essential element in dye-sensitized photoelectrosynthesis cells for the generation of solar fuels by water splitting and CO2 reduction to CO, other oxygenates, or hydrocarbons. Phosphonic acid derivatives provide a basis for stable chemical binding on metal oxide surfaces. We report here the efficient synthesis of 4,4′-bis(diethylphosphonomethyl)-2,2′-bipyridine and 4,4′-bis(diethylphosphonate)-2,2′-bipyridine, as well as the mono-, bis-, and tris-substituted ruthenium complexes, [Ru(bpy)2(Pbpy)]2+, [Ru(bpy)(Pbpy)2]2+, [Ru(Pbpy)3]2+, [Ru(bpy)2(CPbpy)]2+, [Ru(bpy)(CPbpy)2]2+, and [Ru(CPbpy)3]2+ [bpy = 2,2′-bipyridine; Pbpy = 4,4′-bis(phosphonic acid)-2,2′-bipyridine; CPbpy = 4,4′-bis(methylphosphonic acid)-2,2′-bipyridine].
103 citations
TL;DR: An organic-inorganic bio-hybrid bead composite was fabricated by trapping and condensing amorphous silica into the network structures of calcium ion cross-linked alginate (CA) and Xanthan gum (XG) gel beads as mentioned in this paper.
89 citations
TL;DR: The results show that calcium not only can stabilize carbon sp2 hybridization at a larger range of pressure but also can contribute in superconducting behavior, which would further ignite experimental and theoretical interest in alkaline–earth metal carbides to uncover their peculiar physical properties under extreme conditions.
Abstract: Carbon can exist as isolated dumbbell, 1D chain, 2D plane, and 3D network in carbon solids or carbon-based compounds, which attributes to its rich chemical binding way, including sp-, sp(2)-, and sp(3)-hybridized bonds. sp(2)-hybridizing carbon always captures special attention due to its unique physical and chemical property. Here, using an evolutionary algorithm in conjunction with ab initio method, we found that, under compression, dumbbell carbon in CaC2 can be polymerized first into 1D chain and then into ribbon and further into 2D graphite sheet at higher pressure. The C2/m structure transforms into an orthorhombic Cmcm phase at 0.5 GPa, followed by another orthorhombic Immm phase, which is stabilized in a wide pressure range of 15.2-105.8 GPa and then forced into MgB2-type phase with wide range stability up to at least 1 TPa. Strong electron-phonon coupling λ in compressed CaC2 is found, in particular for Immm phase, which has the highest λ value (0.562-0.564) among them, leading to its high superconducting critical temperature Tc (7.9∼9.8 K), which is comparable with the 11.5 K value of CaC6. Our results show that calcium not only can stabilize carbon sp(2) hybridization at a larger range of pressure but also can contribute in superconducting behavior, which would further ignite experimental and theoretical interest in alkaline-earth metal carbides to uncover their peculiar physical properties under extreme conditions.
67 citations
TL;DR: Four noble-gas compounds NgBeS and the BeS(2) molecule are identified on the basis of the S-34 isotopic substitution, DFT and CCSD(T) theoretical predictions, and a comparison of noble- gas substitution.
Abstract: Laser-ablated beryllium atom has been codeposited at 4 K with hydrogen sulfide in excess noble gas matrices. Four noble-gas compounds NgBeS (Ng = Ne, Ar, Kr, Xe) and the BeS2 molecule are identified on the basis of the S-34 isotopic substitution, DFT and CCSD(T) theoretical predictions, and a comparison of noble-gas substitution. The agreement between the experimental and calculated vibrational frequencies supports the identification of these molecules. The dissociation energies are calculated at 1.6, 12.6, 10.7, and 13.4 kcal/mol for NeBeS, ArBeS, KrBeS, and XeBeS, respectively, at the CCSD(T) level. The BeS Lewis acid molecule favors strong chemical binding between the Be and Ng atoms.
55 citations
TL;DR: A high aspect ratio silicon nanowire (SiNW) sensing membrane modified with amorphous indium-gallium-zincoxide nanoparticles (IGZO NPs) was developed for use in extended-gate field effect transistor (EGFET) pH sensors as mentioned in this paper.
Abstract: A high aspect ratio silicon nanowire (SiNW) sensing membrane modified with amorphous indium–gallium–zinc–oxide nanoparticles (IGZO NPs) was developed for use in extended-gate field-effect transistor (EGFET) pH sensors. The IGZO/SiNWs sensing membranes were first fabricated using the Ag-assisted electroless etching technique and were then decorated with IGZO NPs by sputtering in five separate batches for 3, 6, 9, 12 and 15 min to improve the pH sensing properties. SEM, TEM and FTIR spectroscopy were used to respectively analyze surface morphology, crystallinity and chemical binding. The IGZO NPs provided more oxygen-related binding sites than the pristine SiNWs to adsorb additional H + ions, thus effectively improving pH sensitivity. The 9 min IGZO/SiNW sensor exhibited the best sensitivity of 50 mV/pH, an improvement of about 39% over that of the pristine SiNW sensor (36 mV/pH). The IGZO/SiNW sensor exhibited good pH sensing properties and stability that had potential for mass production in disposable biosensors.
50 citations
TL;DR: The authors showed that mesoporous silica and purely siliceous zeolites with voids of molecular dimensions catalyze NO oxidation by O2 at near ambient temperatures (263-473 K) with reaction orders in NO and O2 identical to those for homogeneous routes and with negative apparent activation energies.
Abstract: Mesoporous silica and purely siliceous zeolites with voids of molecular dimensions (MFI, CHA, BEA) catalyze NO oxidation by O2 at near ambient temperatures (263–473 K) with reaction orders in NO and O2 identical to those for homogeneous routes and with negative apparent activation energies. These findings reflect the stabilization of termolecular transition states by physisorption on surfaces or by confinement within voids in processes mediated by van der Waals forces and without the involvement of specific binding sites. Such interactions lead to the enthalpic stabilization of transition states relative to the gaseous reactants; such enthalpic benefits compensate concomitant entropy losses upon confinement because of the preeminent role of enthalpy in Gibbs free energies at low temperatures. These data and their mechanistic interpretation provide clear evidence for the mediation of molecular transformations by confinement without specific chemical binding at active sites.
40 citations
TL;DR: A diffusion-reaction model solved by means of molecular dynamics and density functional theory calculations provides novel insight into the transport of small ligands in proteins, finding that upon reduction of CO2 to CO, the newly formed Fe-hydroxy ligand greatly strengthens the hydrogen-bond network.
Abstract: The transport of small ligands to active sites of proteins is the basis of vital processes in biology such as enzymatic catalysis and cell signaling, but also of more destructive ones including enzyme inhibition and oxidative damage. Here, we show how a diffusion-reaction model solved by means of molecular dynamics and density functional theory calculations provides novel insight into the transport of small ligands in proteins. In particular, we unravel the existence of an elusive, dynamically formed gas channel, which CO2 takes to diffuse from the solvent to the active site (C-cluster) of the bifunctional multisubunit enzyme complex carbon monoxide dehydrogenase/acetyl-CoA synthase (CODH/ACS). Two cavities forming this channel are temporarily created by protein fluctuations and are not apparent in the X-ray structures. The ligand transport is controlled by two residues at the end of this tunnel, His113 and His116, and occurs on the same time scale on which chemical binding to the active site takes place (0.1-1 ms), resulting in an overall binding rate on the second time scale. We find that upon reduction of CO2 to CO, the newly formed Fe-hydroxy ligand greatly strengthens the hydrogen-bond network, preventing CO from exiting the protein through the same way that CO2 takes to enter the protein. This is the basis for directional transport of CO from the production site (C-cluster of CODH subunit) to the utilization site (A-cluster of ACS subunit). In view of these results, a general picture emerges of how large proteins guide small ligands toward their active sites.
TL;DR: The data suggests that OBPs like AcerASP2 might make a large contribution toward assisting the honeybee in sensing and foraging flowers, and A. cerana has evolved a good circadian rhythm to perceive a flower's odor following the fluctuation of temperature in the olfactory system.
TL;DR: In this paper, an intake study on single walled carbon nanotubes (SWCNTs)-tin oxide (SnO 2 ) nano composite films has been performed, where the composite is prepared on glass substrates in hydrogen atmosphere by electron beam evaporation (e-beam) technique.
TL;DR: In this paper, the use of a 1.5μm thermally nitrided Cr interlayer was examined as an effective diffusion barrier throughout the CVD process, and the formation of phases within the interlayer during nitridation and diamond CVD was investigated by complementary techniques: SEM, XRD, XPS, SIMS and Raman spectroscopy.
TL;DR: It is concluded that adding iron(III)chloride in these amounts to the surface water of a lake can potentially be a useful restoration method.
Abstract: Eutrophication has caused a decline of charophyte species in many shallow lakes in Europe. Even though external inputs of phosphorus are declining, internal loading of P from the sediment seems to delay the recovery of these systems. Iron is a useful chemical binding agent to combat internal phosphorus loading. However, the effects of iron addition on charophytes are not yet known. In this study we experimentally tested the potential toxicity of iron(III)chloride (FeCl3) on two different charophytes, Chara virgata Kutzing and Chara globularis Thuiller added at the concentration of 20 g Fe m−2 and 40 g Fe m−2 to the surface water. C. virgata growth was not significantly affected, whereas C. globularis growth significantly decreased with increasing iron concentrations. Nonetheless, biomass of both species increased in all treatments relative to starting conditions. The decrease of C. globularis biomass with high iron additions may have been caused by a drop in pH and alkalinity in combination with iron induced light limitation. Iron addition over a longer time scale, however, will not cause this rapid drop in pH. Therefore, we conclude that adding iron(III)chloride in these amounts to the surface water of a lake can potentially be a useful restoration method.
Journal Article•
TL;DR: In this article, the formation of Friedel's salt is the main chemical binding, and physical adsorption is mainly controlled by C-S-H gel, there are some other factors influencing chloride binding, such as fly ash, slag and silica fume.
Abstract: When chloride ions are introduced into cement-based materials,some of chloride ions interact with the hydration products,and some of chloride ions absorb to the hydration products or pore wall.The former is called chloride chemical binding,and the latter is called chloride physical adsorption,they are collectively referred to the chloride binding.The formation of Friedel’s salt is the main chemical binding,physical adsorption is mainly controlled by C–S–H gel.There are some other factors influencing chloride binding.Some supplementary cement materials(i.e.,fly ash,slag and silica fume) also affect chloride binding notably.Due to the chloride binding,it is expected that there should be microstructural changes in cement-based materials.By knowing the chloride binding and the change of microstructure when chloride ions are introduced into cement-base materials well,we could provide a scientific basis for the service life design and prediction of reinforced concrete structures.
TL;DR: The findings provide a firm basis for the design of site-directed mutants that are suitable for the reliable generation of PCSs in proteins with paramagnetic lanthanides.
Abstract: The previously published IDA-SH and NTA-SH tags are small synthetic lanthanide-binding tags derived from cysteine, which afford site-specific lanthanide labelling by disulfide-bond formation with a cysteine residue of the target protein Following attachment to a single cysteine in an α-helix, sizeable pseudocontact shifts (PCS) can be observed, if the lanthanide is immobilized by additional coordination to a negatively charged amino-acid side chain that is located in a neighboring turn of the helix To identify the best labelling strategy for PCS measurements, we performed a systematic study, where IDA-SH or NTA-SH tags were ligated to a cysteine residue in position i of an α-helix, and aspartate or glutamate residues were placed in the positions i − 4 or i + 4 The largest anisotropy components of the magnetic susceptibility tensor were observed for an NTA-SH tag in position i with a glutamate residue in position i − 4 While the NTA-SH tag produced sizeable PCSs regardless of the presence of nearby carboxyl groups of the protein, the IDA-SH tag generated a good lanthanide binding site only if an aspartate was placed in position i + 4 The findings provide a firm basis for the design of site-directed mutants that are suitable for the reliable generation of PCSs in proteins with paramagnetic lanthanides
TL;DR: The determination of ideal decontamination protocols is of utmost importance to reduce morbidity and mortality, however, even expeditious standard washing procedures post dermal chemical exposure often fails to remove chemicals.
Abstract: Cutaneously directed chemical warfare agents can elicit significant morbidity and mortality. The optimization of prophylactic and therapeutic interventions counteracting these agents is crucial, and the development of decontamination protocols and methodology of post dermal exposure risk assessments would be additionally applicable to common industrial and consumer dermatotoxicants. Percutaneous (PC) penetration is often considered a simple one-step diffusion process but presently consists of at least 15 steps. The systemic exposure to an agent depends on multiple factors and the second part of this review covers absorption and excretion kinetics, wash and rub effects, skin substantivity and transfer, among others. Importantly, the partitioning behavior and diffusion through the stratum corneum (SC) of a wide physicochemical array of compounds shows that many compounds have approximately the same diffusion coefficient which determines their percutaneous absorption in vivo. After accounting for anatomical variation of the SC, the penetration flux value of a substance depends mainly on its SC/vehicle partition coefficient. Additionally, the SC acts as a 'reservoir' for topically applied molecules, and tape stripping methodology can quantify the remaining chemical in the SC which can predict the total molecular penetration in vivo. The determination of ideal decontamination protocols is of utmost importance to reduce morbidity and mortality. However, even expeditious standard washing procedures post dermal chemical exposure often fails to remove chemicals. The second part of this overview continues to review percutaneous penetration extending insights into the complexities of penetration, decontamination and potential newer assays that may be of practical importance.
TL;DR: The hypothesis that four water molecules are present in the binding cavity of thapsigargin in sarco/endoplasmic reticulum calcium ATPase (SERCA) and mediate an extensive hydrogen-bonding network is verified by measuring the affinity of newly synthesized model compounds, which are prevented from participating in such water-mediated interactions as hydrogen- bond donors.
Abstract: A crystal structure suggests four water molecules are present in the binding cavity of thapsigargin in sarco/endoplasmic reticulum calcium ATPase (SERCA). Computational chemistry indicates that three of these water molecules mediate an extensive hydrogen-bonding network between thapsigargin and the backbone of SERCA. The orientation of the thapsigargin molecule in SERCA is crucially dependent on these interactions. The hypothesis has been verified by measuring the affinity of newly synthesized model compounds, which are prevented from participating in such water-mediated interactions as hydrogen-bond donors.
TL;DR: In this paper, the adsorption of 4-nitroanisole on silver colloidal nanoparticles was investigated by surfaceenhanced Raman spectroscopy (SERS).
Abstract: The adsorption of 4-nitroanisole on silver colloidal nanoparticles was investigated by surface-enhanced Raman spectroscopy (SERS). Actually, the chemical binding with a metal substrate may play a role in changing the electronic structure of this molecule, which can be considered a push–pull chromophore, because an internal charge-transfer occurs between methoxy and nitrogroup. A SERS signal could be detected only in chloride-activated silver colloids, but the spectrum recorded with green-light excitation was not related to adsorbed 4-nitroanisole, but to its azoderivative, formed by photoreduction of the nitrogroup on the surface of the silver substrate. Copyright © 2013 John Wiley & Sons, Ltd.
TL;DR: The electrochromic performance of MoO3 films formed on ITO coated glass substrates was studied and achieved the optical modulation of about 13% with color efficiency of about 20 cm2/C.
Abstract: Molybdenum oxide (MoO 3) films were deposited on glass and silicon substrates held at temperature 473 K by RF magnetron sputtering of molybdenum target at various oxygen partial pressures in the range
TL;DR: Results indicate that PI polyamide could bind to RNA with a 2 log lower binding affinity than its DNA-binding affinity, which may be associated with differences of secondary structure and chemical binding properties between target RNA and DNA.
Abstract: Pyrrole-imidazole (PI) polyamides are a novel group of gene-silencing compounds, which bind to a minor groove of double stranded (ds)DNA in a sequence-specific manner. To explore the RNA binding properties of PI polyamides targeting rat transforming growth factor-β1 (TGF-β1 Polyamide) and influenza A virus (PA polyamide), we designed dsRNAs with an identical sequence to the target DNA and analyzed RNA binding properties of the polyamide. Biacore assay showed fast binding of TGF-β1 Polyamide to the dsRNA, whereas mismatch polyamide did not bind to the dsRNA. Dissociation equilibrium constant (KD) value was 6.7×10(-7) of the target dsRNA. These results indicate that PI polyamide could bind to RNA with a 2 log lower binding affinity than its DNA-binding affinity. We designed a PI polyamide targeting the panhandle stem region of influenza A virus. KD value of the PI polyamide to dsRNA targeting influenza A virus was 4.6×10(-7). Gel-shift assay showed that TGF-β1 and PA polyamides bound to the appropriate dsDNA, whereas these PI polyamides did not show obvious gel-shift with the appropriate dsRNA. Structural modeling suggests that PI polyamide binds to the appropriate B-form dsDNA in the minor groove, whereas it does not fit in the minor groove to dsRNA. Thus PI polyamides have a lower binding affinity with target dsRNA than they do with dsDNA. The distinct binding properties of PI polyamides to dsRNA and dsDNA may be associated with differences of secondary structure and chemical binding properties between target RNA and DNA.
TL;DR: The consequences of electron energy level degeneracy on the conductance and the chemical force between two bodies at the atomic scale are shown and a square relation G∝F2 arises as a consequence of quantum degeneracy between the interacting frontier states of the scanning tip and a surface atom.
Abstract: Quantum degeneracy is an important concept in quantum mechanics with large implications to many processes in condensed matter. Here, we show the consequences of electron energy level degeneracy on the conductance and the chemical force between two bodies at the atomic scale. We propose a novel way in which a scanning probe microscope can detect the presence of degenerate states in atomic-sized contacts even at room temperature. The tunneling conductance $G$ and chemical binding force $F$ between two bodies both tend to decay exponentially with distance in a certain distance range, usually maintaining direct proportionality $G\ensuremath{\propto}F$. However, we show that a square relation $G\ensuremath{\propto}{F}^{2}$ arises as a consequence of quantum degeneracy between the interacting frontier states of the scanning tip and a surface atom. We demonstrate this phenomenon on the $\mathrm{Si}(111)\mathrm{\text{\ensuremath{-}}}(7\ifmmode\times\else\texttimes\fi{}7)$ surface reconstruction where the Si adatom possesses a strongly localized dangling-bond state at the Fermi level.
TL;DR: A very weak Cu···O interaction is revealed between the copper-carbonate layers that is nevertheless stabilizing (bonding) and may serve as a possible pathway for antiferromagnetic interactions.
Abstract: Chemical binding in a mixed copper sodium carbonate Na2Cu(CO3)2, a layered material showing ferromagnetic intralayer exchange and weak antiferromagnetic interlayer coupling, was examined within the topological analysis of experimental (from high-resolution X-ray diffraction) and theoretical (from periodic quantum chemical calculations) electron density functions in its crystal. Together with modeling of a superexchange pathway within the LSDA and DFT+U approach, the results obtained reveal a very weak Cu···O interaction (0.5 kcal/mol worth) between the copper–carbonate layers that is nevertheless stabilizing (bonding) and may serve as a possible pathway for antiferromagnetic interactions.
TL;DR: The results demonstrate that an efficient immobilization of L. lactis cells to chitin is possible for industrial scale repeated cycle or continuous nisin fermentation.
Abstract: In this study, nisin producer Lactococcus lactis strains displaying cell surface chitin-binding domain (ChBD) and capable of immobilizing to chitin flakes were constructed. To obtain ChBD-based cell immobilization, Usp45 signal sequence with ChBD of chitinase A1 enzyme from Bacillus circulans was fused with different lengths of PrtP (153, 344, and 800 aa) or AcmA (242 aa) anchors derived from L. lactis. According to the whole cell ELISA analysis, ChBD was successfully expressed on the surface of L. lactis cells. Scanning electron microscope observations supported the conclusion of the binding analysis that L. lactis cells expressing the ChBD with long PrtP anchor (800 aa) did bind to chitin surfaces more efficiently than cells with the other ChBD anchors. The attained binding affinity of nisin producers for chitin flakes retained them in the fermentation during medium changes and enabled storage for sequential productions. Initial nisin production was stably maintained with many cycles. These results demonstrate that an efficient immobilization of L. lactis cells to chitin is possible for industrial scale repeated cycle or continuous nisin fermentation.
TL;DR: The findings suggest that NAC reduces the toxicity of the cationic antibacterial monomer MDPB, and adduct formation is partially responsible for the detoxification ability of NAC against MDP B-induced cell damage.
TL;DR: In this article, the effect of substrate temperature (Ts) on the structure, chemical binding configuration, surface morphology, composition, optical and electrical properties of NiO films was investigated and it was suggested that the growth temperature affects the properties of the NiO film.
Abstract: Nickel oxide (NiO) films were deposited on Corning 7059 glass substrates using DC reactive magnetron sputtering at different substrate temperatures in the range 30 o C to 400 o C. The effect of substrate temperature (Ts) on the structure, chemical binding configuration, surface morphology, composition, optical and electrical properties of NiO films was investigated. X-ray diffraction studies indicated that as Ts increased above 200 o C; the preferred orientation (220) intensity was increased and had a stable cubic structure. The X-ray photoelectron spectroscopy studies revealed the grown films have single phase of NiO. From the morphological studies, it was observed that the grain size and root mean square roughness was increased with Ts. It is suggested that the growth temperature affects the properties of NiO film. Higher substrate temperature induces larger grain size and more perfect crystalline structure, which lead to low resistivity.
TL;DR: This work combines chemical binding kinetics with (virological) stoichiometries to better explain virus neutralisation by antibody binding and gives a more subtle explanation of kinetic neutralisation curves in terms of single-hit and multi-hit kinetics.
Abstract: Antibodies binding to the surface of virions can lead to virus neutralisation. Different theories have been proposed to determine the number of antibodies that must bind to a virion for neutralisation. Early models are based on chemical binding kinetics. Applying these models lead to very low estimates of the number of antibodies needed for neutralisation. In contrast, according to the more conceptual approach of stoichiometries in virology a much higher number of antibodies is required for virus neutralisation by antibodies. Here, we combine chemical binding kinetics with (virological) stoichiometries to better explain virus neutralisation by antibody binding. This framework is in agreement with published data on the neutralisation of the human immunodeficiency virus. Knowing antibody reaction constants, our model allows us to estimate stoichiometrical parameters from kinetic neutralisation curves. In addition, we can identify important parameters that will make further analysis of kinetic neutralisation curves more valuable in the context of estimating stoichiometries. Our model gives a more subtle explanation of kinetic neutralisation curves in terms of single-hit and multi-hit kinetics.
TL;DR: This chapter provides an overview of quantitative studies of chemical binding and reactivity at bilayers, aiming to outline the ways bilayer properties alter these processes.
Abstract: A new era of synthetic biology has rekindled interest in achieving a better understanding of simple chemical processes that occur at bilayer membranes. Applying the principles of physical organic chemistry to the analysis of binding and reactivity at bilayers should provide this deeper insight and supplying predictive tools for the design of complex self-assembled systems involving bilayers. In this chapter, we provide an overview of quantitative studies of chemical binding and reactivity at bilayers, aiming to outline the ways bilayer properties alter these processes. Surface charges and low polarity are commonly acknowledged influences on binding and reactivity, but other properties that arise from the liquid crystalline nature of the bilayer, such as phase behavior, anisotropy, and lipid clustering, are also important. In addition, bilayer membranes have a concentrating and orientating effect, producing high effective concentrations of membrane-bound receptors and reagents; studies that elucidate the effect of these high local concentrations on inter-/intramembrane binding or reactivity are described. Then to conclude, a summary of how bilayer properties affect binding and reactivity is presented.
TL;DR: In this paper, a density-functional theory (DFT) analysis of Ni-based catalysts for deactivation is presented, where the authors calculate the chemical binding energy of carbon as a function of its surface coverage and study the local chemical environment via its electronic structure.