Iron Speciation in Organic Matter Fractions Isolated from Soils Amended with Biochar and Organic Fertilizers.

The role and distribution of iron (Fe) species in physical soil fractions have received remarkably little attention in field-scale systems. Here, we identify and quantify the Fe phases into two fractions (fine sand, FSa, and fine silt and clay, FSi + Cl), isolated from an agricultural soil unamended and amended with different organic materials, by Fe K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy. The linear combination fitting and wavelet transform of EXAFS data revealed noticeable differences between unamended FSa and FSi + Cl fractions. Specifically, the FSi + Cl fraction was mainly characterized by ferrihydrite (48%) and Fe(III)-soil organic matter (SOM) complexes (37%), whereas in the FSa fraction, ferrihydrite still represented a major phase (44%), with a lower contribution from Fe(III)-SOM (18%). In the FSa fraction, the addition of the organic amendments resulted in an increase of Fe-SOM complexes (31-35%) and a decrease of ferrihydrite (28-29%). By contrast, in the amended FSi + Cl fractions, the added organic matter led to negligible changes in percent ferrihydrite. Therefore, regardless of the amendment type, the addition of organic matter to soil increased the capability of the coarse fraction (FSa) to stabilize organic carbon, thus pointing out that the role of FSa in carbon sequestration in agricultural soils at a global scale may be overlooked.

Physicochemical Properties of a Bi-aromatic Heterocyclic-Azo/BSA Hybrid System at the Air-Water Interface.

The interaction of a heterocyclic azo compound with itself and with bovine serum albumin (BSA) is realized by probing the structural modifications in Langmuir (L) monolayers and Langmuir-Blodgett (LB) films. It was found from the pressure-area/molecule isotherms that the elastic, thermodynamic, and hysteretic properties of the pure azo L monolayer were strongly altered due to the variation of temperature and pH of subphase water. In addition to that, the modification of such properties of the azo L monolayer due to mixing with BSA was also studied. The incorporation of BSA within the azo molecular assembly reduced the elasticity of that assembly. Such reduction of in-plane elasticity of the pure azo monolayer can also be achieved by reducing the temperature and pH of subphase water without adding BSA. A reduction in area per molecule of the azo assembly at the air-water interface associated with the conformational change from horizontal to vertical orientation facilitating π-π interaction was observed with increase in temperature and pH of the subphase. Such parameters also affected the interactions between azo and BSA molecules within the azo/BSA binary system. The structures of pure azo and binary films can be determined after they are transferred to hydrophilic and hydrophobic Si surfaces using the LB technique. Their out-of-plane and in-plane structures, as extracted from two complementary surface sensitive techniques, X-ray reflectivity and atomic force microscopy, were found to be strongly dependent on mixing with BSA, subphase pH, temperature, and substrate nature.

A multidisciplinary study unveils the nature of a Roman ink of the I century AD.

A multi-instrumental approach combining highly sensitive Synchrotron Radiation-based techniques was used to provide information on the real composition of a dry black ink powder found in a bronze inkwell of the first century AD. The presence of Pb, Cu and Fe in the powder, revealed by XRF and ICP-OES data, leads to raise several hypotheses on their origin. The inkpot and its lid were also investigated by Hand-Held XRF, revealing a bronze alloy (Cu-Sn) with a certain amount of Fe and Pb. The lid was found to be particularly enriched in lead. XRPD, XAS and FTIR measurements showed a substantial presence of silicates and common clay minerals in the ink along with cerussite and malachite, Pb and Cu bearing-carbonates, respectively. These evidences support the hypothesis of an important contamination of the ink sample by the burial environment (soil) and the presence of degradation products of the bronze inkpot. The combined use of IR, Raman, and GC-MS evidenced that the black ink is mainly composed of amorphous carbon deriving from the combustion of organic material mixed with a natural binding agent, Arabic gum.

Synthesis of some tropane-based compounds targeting colon cancer.

Background: In continuation of a previous work concerned with the anticancer activity of some 8-alkyl-2,4-bisarylidene-8-nortropan-3-ones, this work focuses on further modification to the tropane/pyran fused skeleton aiming to obtain improved anticancer activity. Methodology: Reaction of 8-alkyl-2,4-bisarylidene-8-nortropan-3-ones 1-21 with malononitrile under basic conditions afforded tropane/pyran hybrids 22-40 and tropane/pyridine hybrids 41, 42. X-ray crystallography for compounds 22 and 41 as representative examples confirmed their structures. They were tested for their anticancer activity in the HCT116 cell line. Results: Compounds 26 and 33 were the most active compounds with IC50 values of 3.39 and 0.01 µM against HCT116. Moreover, they revealed cyclin-dependent kinase-2 (CDK2) inhibition with IC50 = 104.91 and 49.13 nM, respectively. Furthermore, molecular docking of compounds 26 and 33 in the active site of CDK2 confirmed the obtained results. Conclusion: Tropane/pyran scaffold can be considered as a promising core for anticancer agents acting as CDK2 inhibitors.

Structure and Elastic Properties of an Unsymmetrical Bi-Heterocyclic Azo Compound in the Langmuir Monolayer and Langmuir-Blodgett Film.

We study the structure and elastic properties of the bi-heterocyclic azo compound at the air-water interface through surface pressure (π)-area (A) isotherm recording followed by transferring them on hydrophilic and hydrophobic Si surfaces by the Langmuir-Blodgett (LB) deposition method. A substantial change in the area/molecule is observed as a function of subphase pH and temperature. Such parameters strongly influence intramolecular interactions within azo molecules and the interactions between azo molecules and water that manifested in higher surface activity at low temperature and high pH, which in turn modifies the elasticity of azo assembly at the air-water interface. A large pH-dependent hysteresis with negative change in entropy, indicating molecular rearrangements, is observed. Molecular assembly formed at the air-water interface is then transferred onto hydrophilic and hydrophobic Si surfaces at two different surface pressures (5 and 30 mN/m) by the LB technique. The structural analysis performed by X-ray reflectivity and atomic force microscopy techniques suggests that the LB films exhibit an abrupt layered structure on hydrophilic Si, whereas an overall rough film is formed on hydrophobic Si. The coverage and compactness of individual layers are found to increase with the deposition pressure (5 to 30 mN/m).

Titanium-based potassium-ion battery positive electrode with extraordinarily high redox potential.

The rapid progress in mass-market applications of metal-ion batteries intensifies the development of economically feasible electrode materials based on earth-abundant elements. Here, we report on a record-breaking titanium-based positive electrode material, KTiPO4F, exhibiting a superior electrode potential of 3.6 V in a potassium-ion cell, which is extraordinarily high for titanium redox transitions. We hypothesize that such an unexpectedly major boost of the electrode potential benefits from the synergy of the cumulative inductive effect of two anions and charge/vacancy ordering. Carbon-coated electrode materials display no capacity fading when cycled at 5C rate for 100 cycles, which coupled with extremely low energy barriers for potassium-ion migration of 0.2 eV anticipates high-power applications. Our contribution shows that the titanium redox activity traditionally considered as "reducing" can be upshifted to near-4V electrode potentials thus providing a playground to design sustainable and cost-effective titanium-containing positive electrode materials with promising electrochemical characteristics.

Electronic structure of MAPbI3 and MAPbCl3: importance of band alignment.

Since their first appearance, organic-inorganic perovskite absorbers have been capturing the attention of the scientific community. While high efficiency devices highlight the importance of band level alignment, very little is known on the origin of the strong n-doping character observed in the perovskite. Here, by means of a highly accurate photoemission study, we shed light on the energy alignment in perovskite-based devices. Our results suggest that the interaction with the substrate may be the driver for the observed doping in the perovskite samples.

Synthesis, structural and antimicrobial studies of binary and ternary complexes of a new tridentate thiosemicarbazone.

A new thiosemicarbazone ligand was synthesized and characterized using spectroscopic techniques (UV-Vis and IR) and synchrotron x-ray powder diffraction. With M2+ = Mn2+, Zn2+ and Cd2+, coordination compounds of the type (M[L]2) were isolated. In the presence of sodium dithiocarbamate salts (NadiEtdtc.3H2O = sodium diethyldithiocarbamate trihydrate and Napipdtc = sodium piperidinedithiocarbamate), Zn2+ and Cd2+ were able to form ternary octahedral complexes where each metal binds a deprotonated (thiosemicarbazone) ligand, a monobasic dithiocarbamate ligand and a water molecule. In vitro biological evaluation tests of the free HL ligand and its metal complexes against selected fungal and bacterial cultures were performed. Compared with HL, the complexes displayed enhanced biological activities and ternary Zn (II) complexes displayed comparable antibacterial activities to the chloramphenicol standard.

Vitamin C/Stearic Acid Hybrid Monolayer Adsorption at Air-Water and Air-Solid Interfaces.

Because of the antioxidant activity of vitamin C (Vit C) polar heads, they can be used as a protective agent for fatty acids. Hence, the study on the growth of Vit C/stearic acid (SA) mixed binary films at air-water interface (known as Langmuir monolayer) and air-solid interface (known as Langmuir-Blodgett films) is of paramount interest. Although Vit C is situated at subsurface beneath SA molecules and interacts via hydrogen bonding between the hydroxyl groups of Vit C and SA, several Vit C molecules may infiltrate within SA two-dimensional matrix at the air-water interface. The increased mole fraction of Vit C (0.125-0.5) and the reduction of temperature (from 22 to 10 °C) of the subphase water result in an increase in the amount of adsorbed Vit C at the air-water interface. The surface pressure (π)-area (A) isotherms illustrate that such inclusion of Vit C provokes a spreading out of Vit C/SA binary monolayers, which leads to an alteration of different physicochemical parameters such as elasticity, Gibbs free energy of mixing, enthalpy, entropy, interaction energy parameter, and activity coefficient. However, being polar in nature, the transfer of pure Vit C on substrates gets affected. It can be transferred onto substrate by mixing suitably with SA as confirmed by infrared spectra. Their structures, extracted X-ray reflectivity, and atomic force microscopy (topography and phase imaging) are found to be strongly dependent on the nature of the substrate (hydrophilic and hydrophobic).

Chitosan-fatty acid interaction mediated growth of Langmuir monolayer and Langmuir-Blodgett films.

The interaction of chitosan with bio-membranes, which plays important role in deciding its use in biological applications, is realized by investigating the interaction of chitosan with stearic acid (fatty acid) in Langmuir monolayers (at air-water interface) and Langmuir-Blodgett (LB) films (after transferring it onto solid substrate). It is found from the pressure-area isotherms that the chitosan insertion causes an expansion of chitosan-fatty acid hybrid monolayers, which reduces the elasticity and make the film heterogeneous. It is likely that at low surface pressure chitosan is situated at the interface, interacting with stearic acid molecules via electrostatic and hydrophobic interactions whereas at high pressure chitosan mainly located at subsurface beneath stearic acid molecules. In the latter case the interaction is predominantly electrostatic yielding very small contribution to the surface pressure. The reduction of temperature of the subphase water allows more number of chitosan molecules to reach surface to increase the pressure/interaction. On the other hand, although pure chitosan is found difficult to relocate on the substrate from air-water interface due to its hydrophilic-like nature, it alongside stearic acid (amphiphilic molecules) can be transferred onto substrate using LB technique as evident from infrared spectra. Their out-of-plane and in-plane structures, as extracted from two complementary surface sensitive techniques- X-ray reflectivity and atomic force microscopy, are found strongly dependent on the chitosan mole fraction and the deposition pressure. These analysis of the film-structure will essentially allow one to model the system better and provide better insight into the interaction.

Visualization by cryo-electron microscopy of genomic RNA that binds to the protein capsid inside bacteriophage MS2.

The icosahedrally symmetrized structure of bacteriophage MS2 as determined by cryo-electron microscopy (EM) reveals the presence of genomic RNA that attaches to coat-protein dimers. Earlier X-ray diffraction studies revealed similar interactions between the unique operator hairpin of the MS2 genomic RNA and the coat-protein dimer. This observation leads us to conclude that not only the operator, but also many other RNA sequences in the genome of MS2, are able to bind to the coat-protein dimer. A substantial number of potential coat-protein-dimer binding sites are present in the genome of MS2 that can account for the observed RNA densities in the EM map. Moreover, it appears that these stem-loop structures are able to bind in a similar fashion to the coat protein dimer as the wild-type operator hairpin. The EM map also shows additional density between the potential operator-binding sites, linking the RNA stem-loops together to form an icosahedral network around the 3 and 5-fold axes. This RNA network is bound to the inside of the MS2 capsid and probably influences both capsid stability and formation, supporting the idea that capsid formation and RNA packaging are intimately linked to each other.

Crystal structure of an empty capsid of turnip yellow mosaic virus.

Empty capsids (artificial top component) of turnip yellow mosaic virus were co-crystallized with an encapsidation initiator RNA hairpin. No clear density was observed for the RNA, but there were clear differences in the conformation of a loop of the coat protein at the opening of the pentameric capsomer (formed by five A-subunits) protruding from the capsid, compared to the corresponding loop in the intact virus. Further differences were found at the N terminus of the A-subunit. These differences have implications for the mechanism of decapsidation of the virus, required for infection.

Recycling of aborted ribosomal 50S subunit-nascent chain-tRNA complexes by the heat shock protein Hsp15.

When heat shock prematurely dissociates a translating bacterial ribosome, its 50S subunit is prevented from reinitiating protein synthesis by tRNA covalently linked to the unfinished protein chain that remains threaded through the exit tunnel. Hsp15, a highly upregulated bacterial heat shock protein, reactivates such dead-end complexes. Here, we show with cryo-electron microscopy reconstructions and functional assays that Hsp15 translocates the tRNA moiety from the A site to the P site of stalled 50S subunits. By stabilizing the tRNA in the P site, Hsp15 indirectly frees up the A site, allowing a release factor to land there and cleave off the tRNA. Such a release factor must be stop codon independent, suggesting a possible role for a poorly characterized class of putative release factors that are upregulated by cellular stress, lack a codon recognition domain and are conserved in eukaryotes.